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Interpreting ecology and behaviour from the vertebrate fossil track record

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Abstract

Fossil tracks represent a direct window onto the lives of extinct organisms, being formed and preserved in situ. Because track morphology is determined by limb motion, foot anatomy and substrate consistency, studies of fossil tracks can provide insight into producer, behaviour and palaeoenvironment. However, each determining factor is subject to variation, either continuous or discrete, and this variation may be co-dependent, making it difficult to correctly interpret a track. In addition to variance from the track-forming variables, tracks and tracksites are subject to further obfuscation because of time averaging, even before the effects of weathering, erosion and exposure are accounted for. This paper presents a dis-cussion of the factors that may confound interpretation of fossil tracks, trackways and tracksites, and reviews experimental studies that have attempted to elucidate and eliminate these sources of confusion.

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... Preserved trackways from these dinosaurs indicate that often their fore-and hindfeet impressions differ in depth (Falkingham et al. 2011b(Falkingham et al. , 2012, implying differential underfoot pressures. Determining foot surface area in these animals can be complex, however, and attribution of specific trackmakers to trackways is notoriously difficult (Farlow, 1992;Clack, 1997;Falkingham, 2014), partly because matching impressions of fully fleshed feet to skeletal remains would require accurate methods of predicting skeletal to skin foot morphology, which is currently difficult and largely speculative (Jannel et al. 2019). Indeed, matching the tracks of extant animals to the correct species is often not straightforwardas illustrated by the existence of field guides produced to help fieldworkers with this problem (e.g. ...
... Assigning specific trackmakers to fossilised trackways is a difficult task (Falkingham, 2014). It is our hope that these results could be used to constrain potential trackmaker identity. ...
... When predicting the skeletal surface area of the feet of extinct animals, and identifying trackmakers, the many complexities of footprint formation must be taken into account. The shape of footprints is determined not only by foot anatomy, but also dynamics of the limbs and substrate consistency (Padian & Olsen, 1984;Minter et al. 2007;Falkingham, 2014). Underfoot pressures (Hatala et al. 2013), centre of mass position (Castanera et al. 2013) and style of locomotion (Hatala et al. 2016) all contribute to variations in limb dynamics, and consequently the morphology of a track. ...
Article
The surface area of feet in contact with the ground is a key morphological feature that influences animal locomotion. Underfoot pressures (and consequently stresses experienced by the foot), as well as stability of an animal during locomotion, depend on the size and shape of this area. Here we tested whether the area of a skeletal foot could predict in vivo soft tissue foot surface area. Computed tomography scans of 29 extant tetrapods (covering mammals, reptiles, birds and amphibians) were used to produce models of both the soft tissues and the bones of their feet. Soft tissue models were oriented to a horizontal plane, and their outlines projected onto a surface to produce two-dimensional silhouettes. Silhouettes of skeletal models were generated either from bones in CT pose or with all autopodial bones aligned to the horizontal plane. Areas of these projections were calculated using alpha shapes (mathematical tight-fitting outline). Underfoot area of soft tissue was approximately 1.67 times that of skeletal tissue area (~ 2 times for manus, ~ 1.6 times for pes, if analysed separately). This relationship between skeletal foot area and soft tissue area, while variable in some of our study taxa, could provide information about the size of the organisms responsible for fossil trackways, suggest what size of tracks might be expected from potential trackmakers known only from skeletal remains, and aid in soft tissue reconstruction of skeletal remains for biomechanical modelling.
... Fossil footprints attributed to Homo erectus are reported from the Danakil Desert, Eritrea from an ancient lake shore deposit dated to ~800 ka (Archaeology News Network, 2016). Additional sites within the Koobi Fora Formation record Pleistocene bipedal hominin and large vertebrate tracks and trackways -including rare examples of trackways produced by swimming hippopotami (Behrensmeyer & Laporte, 1981;Bennett et al., 2009;2014;Brown et al., 2006;Hatala et al., 2017;Roach et al., 2016). ...
... Additional late Pleistocene human track sites from the region include Nahoon (~124 ka) in Eastern Cape Province, and Brenton-on-Sea (~90 ka) and Langbaan Lagoon (~117 ka), both in Western Cape Province (Berger & Hilton-Barber, 2000;Jacobs & Roberts, 2009;Roberts, 2008;Roberts & Berger, 1997). Numerous fossil animal tracks and trackway sites preserved in aeolianites (i.e., from Witsand to Robberg Nature Reserve) that represent contemporary animal genera were also discovered along the Cape south coast (Helm, Cawthra, Combrink, et al., 2020;Helm, Cawthra, Cowling, et al., 2020;Helm, Cawthra, de Vynck, et al., 2019; (Behrensmeyer & Laporte, 1981;Bennett et al., 2009;2014;Brown et al., 2006;hatala et al., 2017;Roach et al., 2016); 4 -sandai Plain (Loboi silts), Lake Bogoria, Kenya (Late Pleistocene) (scott et al., 2008); 5 -Engare sero, Lake natron, Tanzania (5760 ± 30 to 19.1 ± 3.1 ka) (Balashova et al., 2016;hatala et al., 2020;Liutkus-Pierce et al., 2016;Zimmer et al., 2018); 6 -Laetoli, Tanzania (~3.6 Ma) (Day & Wickens, 1980;Leakey, 1978b;Raichlen et al., 2010); 7 -nahoon site, Eastern cape Province, south Africa (~124 ka) (Jacobs & Roberts, 2009;Roberts, 2008); 8 -Brenton-on-sea, Western cape Province, south Africa (~90 ka) ; 9 -still Bay, Western cape Province, south Africa (~90 ka) (helm, cawthra, de Vynck, et al., 2019;Roberts et al., 2008); 10 -Langbaan Lagoon, Western cape Province, south Africa (~117 ka) (Berger & hilton-Barber, 2000;Roberts & Berger, 1997); 11 -namib sand sea, Walvis Bay, namibia (late holocene) (Morse et al., 2013); 12 -cape south coast sites, south Africa (Late Pleistocene) (helm, cawthra, combrink, et al., 2020;helm, cawthra, cowling, et al., 2020;helm, cawthra, de Vynck, et al., 2019;helm et al., 2017;helm et al., cawthra, hattingh, 2019;Roberts, 2008;Roberts et al., 2008Roberts et al., ). et al., 2008. ...
... Such surfaces record a snapshot in time and allow rare, direct observation of ancient inter-and intra-species interaction and behaviour. The discovery of trackways (instead of isolated tracks) would allow additional research into the locomotion style and speed of track makers at Olduvai (Falkingham, 2014;Lockley, 1998). Tracks and skeletal fossils are rarely found in the same strata, and the discovery of additional tracks and trackways would further our palaeoecological understanding of Olduvai Gorge during the early-to mid-Pleistocene. ...
Article
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Large animal tracks, unequivocally attributable to terrestrial mammals, are reported for the first time in sediment from uppermost Bed I (Tuff IF; ∼1.803 million years ago) at Olduvai Gorge, Tanzania. One track in particular (attributed to the ichnogenus Pecoripeda) retains an exceptional level of detail, demonstrating the excellent trackway-preserving potential of the volcanic ash fall (tuff) layers at this important hominin archaeological locality. Olduvai Gorge is renowned for its abundant Plio-Pleistocene (zoo)archaeological discoveries and fossiliferous deposits vis-à-vis studies of human evolution. Fossil trackways, and trace fossils more widely, provide an important additional tool for characterizing ancient ecosystems, which remain underexplored at Olduvai. Considered together with fossil hominin remains, information derived from coeval fossil animal tracks provides additional insight into our ancestors’ behaviour and their interactions with the surrounding palaeoenvironment. A range of large herbivore tracks indicates the availability of nearby resources (i.e., freshwater, vegetation preferred by grazers/browsers). These newly-discovered tracks are of archaeological and palaeontological significance because they highlight the potential for future discovery of animal or hominin tracks and trackways preserved in tuff at Olduvai and in other archaeological localities.
... Footprint morphology is the result of kinematic interactions between the foot and the substrate, which can produce varied track morphologies within the same trackway sequences (Falkingham, 2014;Razzolini et al., 2014;Wings et al., 2016;Lallensack et al., 2016). Thus, kinematic and sedimentological influences can mask true foot morphology, requiring careful consideration of the factors that created a specific track, whether morphological, kinematic, or taphonomic; a difficult task when dealing with the fossil record. ...
... Behavior, taphonomy, and sediment rheology can each greatly affect the shape of a footprint, causing differences even within a single trackway (Thulborn, 1990;Manning, 2004;Falkingham, 2014;Razzolini et al., 2014;Lallensack et al., 2016). To reduce the effects of variability from differing preservation and also the subjectivity of interpreting footprint outlines, each track from the Wapiti Formation is represented by minimum, maximum, and sometimes 'best interpretation' outlines ( Fig. 2; as recommended by Falkingham, 2016). ...
... A sliding semi-landmark approach was chosen because true homology between landmarks amid the curves cannot be assumed, whereas geometric homology of the entire curves can be established on the basis that they represent the outer margins of the foot (Gunz and Mitteroecker, 2013;Bardua et al., 2019). The six homologous landmarks represent: the posterior apex of the heel impression; tip of the impression of digit II; hypex between the impressions of digits II and III; tip of the impression of digit III; hypex between the impressions of digits III and IV; and tip of the impression of digit IV (Fig. 3B), although we acknowledge that hypex positions are particularly variable track features, even within single trackways (Belvedere, 2008;Falkingham, 2014;Wings et al., 2016;Razzolini et al., 2014;Lallensack et al., 2016). Therefore, preservational and kinematic influences on the morphology of each track were individually assessed (see 'non-anatomical influences on track morphology'). ...
Article
Fossil tracks should theoretically capture differences in pedal anatomy between growth stages of the same taxon, particularly those related to the soft tissue of the foot, providing a more realistic view of pedal ontogeny than skeletal material alone. However, recognizing these ontogenetic trajectories is complicated by the influence of preservation and kinematics on track morphology, as well as the inherent difficulty of referring different tracks to a single taxon. Here, we explore differences in track morphology from a collection of tracks attributed to tyrannosaurids from Unit 4 of the Wapiti Formation (upper Campanian) in western Canada. Along with morphology, close geographic and stratigraphic associations suggest that the tracks pertain to similar tyrannosaurid trackmakers. A geometric morphometric analysis of the track outlines reveals size-dependent increase in relative track robusticity, driven primarily by an increase in 'heel' breadth and surface area. This relationship is lost when the dataset is expanded to include tyrannosaurid tracks globally, which we attribute to increased stratigraphic and taxonomic 'noise' within the global dataset that masks the tightly constrained patterns obtained from the Wapiti Formation tracks. Although there is some substrate and kinematic influence on certain aspects of track morphology, we hypothesize that the observed size-dependent relationship reflects genuine expansion in the breadth of the heel soft tissues and probably their overall surface area associated with growth. Increased pedal robusticity likely assisted with weight bearing and locomotor stability as body mass increased over ontogeny, supporting previous hypotheses that some tyrannosaurids underwent a growth-related reduction in relative agility and/or cursorial performance.
... A common goal of track analysis is identifying the most likely trackmaking organisms. However, the overall shape of a track is influenced by some combination of three factors-autopodial anatomy (the shape of the foot), its dynamic motion (how the animal is locomoting), and the conditions of the substrate across which it traverses [59]. Frustratingly, the combination of these factors implies both that a single trackmaking organism can produce a variety of different track morphologies (as seen in the case of individual trackways in [60]) or different organisms can produce similar track morphologies. ...
... Since variations in the shape of dinosaur footprints result from the combination of gross pedal morphology, the motion of the foot through the substrate, the consistency of the substrate, and post-registrational taphonomic processes [40,59], variations in track morphology observed in the trackways and track association the site do not definitively imply that there are multiple trackmaking theropod species at BP1. Using an average of the track lengths in each trackway, the hip heights of the trackmakers for BP1_Twy_02, BP1_Twy_03, and TA_1 were calculated (Table 3). ...
Article
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Dinosaur fossils from the Middle Jurassic are rare globally, but the Isle of Skye (Scotland, UK) preserves a varied dinosaur record of abundant trace fossils and rare body fossils from this time. Here we describe two new tracksites from Rubha nam Brathairean (Brothers’ Point) near where the first dinosaur footprint in Scotland was found in the 1980s. These sites were formed in subaerially exposed mudstones of the Lealt Shale Formation of the Great Estuarine Group and record a dynamic, subtropical, coastal margin. These tracksites preserve a wide variety of dinosaur track types, including a novel morphotype for Skye: Deltapodus which has a probable stegosaur trackmaker. Additionally, a wide variety of tridactyl tracks shows evidence of multiple theropods of different sizes and possibly hints at the presence of large-bodied ornithopods. Overall, the new tracksites show the dinosaur fauna of Skye is more diverse than previously recognized and give insight into the early evolution of major dinosaur groups whose Middle Jurassic body fossil records are currently sparse.
... The preservation of the ichnites is controlled by the substrate conditions, as well as by the trackmakers locomotion (Melchor and Sarjeant, 2004;Falkingham, 2014;Melchor, 2015). Among a complex interaction of variables (Falkingham, 2014), the relative moisture of the substrate is one of the most relevant features (Brand, 1996;Melchor and Sarjeant, 2004;Melchor, 2015). ...
... The preservation of the ichnites is controlled by the substrate conditions, as well as by the trackmakers locomotion (Melchor and Sarjeant, 2004;Falkingham, 2014;Melchor, 2015). Among a complex interaction of variables (Falkingham, 2014), the relative moisture of the substrate is one of the most relevant features (Brand, 1996;Melchor and Sarjeant, 2004;Melchor, 2015). Therefore, the resulting footprint morphologies provide information on water content and substrate rheology (Brand, 1996), factors closely related to the environment. ...
Article
The Middle Triassic successions of coastal and distal alluvial systems are often characterized by the presence of the tetrapod ichnotaxon Rhynchosauroides. Nevertheless, few studies paid attention on the paleoenvironmental implications of this widely distributed ichnogenus. The finding of a new Rhynchosauroides-dominated tracksite opens the window to the use of such footprints in paleoenvironmental studies. The tracksite is located in the active quarry of Pedrera de Can Sallent, at Castellar del Vallès (Catalan Basin, NE Iberian Peninsula). The footprints were recovered from the Middle Muschelkalk detrital unit, composed of a claystone-sandstone-gypsum succession from a sabkha setting of late Anisian-middle Ladinian age. This unit was deposited during a short regression interval within the main Middle Triassic transgression represented by the Muschelkalk facies. The ichnoassociation is composed of Rhynchosauroides isp., and a single, partially preserved, undetermined large footprint. Among Rhynchosauroides specimens, three different preservation states were recognized, corresponding to substrates in (1) subaqueous conditions (surfaces with scarce, deformed, and deeply impressed ichnites), (2) occasionally flooded (mostly trampled surfaces, footprints commonly well preserved), and (3) subaerial exposition (surfaces with few footprints, sometimes corresponding to faint impressions or only preserved by claw marks). The footprint morphological variations of Rhynchosauroides are correlated to substrate rheology and further to the environmental conditions. Rhynchosauroides is a characteristic morphotype that often dominates in the Anisian-Ladinian coastal and distal alluvial settings of several European tracksites. Therefore, these ichnoassociations in such environments, awaiting further detailed analyses, may constitute a distinct ichnocoenosis.
... Based on these morphological analyses, hundreds of ichnotaxa (grouped in ichnogenera and ichnospecies, and sometimes in ichnofamilies as well) have been erected. Nevertheless, in several studies the conditions of the original substrate (e.g., composition, granulometry, original moisture, rheology) where footprints were impressed and the behavior of the trackmakers have not been fully considered, though such factors are the main constraints (together with the autopodia anatomy) of the final track morphology (Falkingham, 2014;Gatesy and Falkingham, 2017;Belvedere et al., 2018;Marchetti et al., 2019a). Therefore, several ichnotaxa have been erected on the basis of extramorphological features, which represent variations not due to the foot anatomy (Peabody, 1948;Haubold, 1996). ...
... Therefore, before doing ichnotaxonomical inferences, the process of autopodia impression in the sediment should be understood (e.g., Gatesy et al., 1999;Falkingham and Gatesy, 2014;Gatesy and Falkingham, 2017;Mujal and Schoch, 2020). In addition, the effects of the substrate conditions at the time of impression should be considered (see also section "Relative Depth Patterns on Permian to Triassic Tetrapod Footprints" below), because they can alter significantly the morphological traits linked to anatomy (Falkingham, 2014). Moreover, a number of other effects occurring after the track recording, such as trace fossil and sedimentary structure superimpositions and the sediment erosion, should be correctly interpreted (e.g., Marty et al., 2009). ...
Article
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In recent years photogrammetry has become an essential tool in the study of tetrapod footprints. Morphological analyses of footprints are interpretative; thus, researchers should use as much information as possible in order to eventually provide an objective conclusion. In this regard, photogrammetry is an extremely helpful tool to avoid potential biases and to better present ichnological data. We review the use of this technique in several Permian and Triassic tetrapod ichnological studies, with considerations on (1) ichnotaxonomy, (2) track-trackmaker correlation, (3) locomotion and/or behavior, (4) substrate induced effects, and (5) preservation of the fossil record and heritage. Furthermore, based on the available three-dimensional (3D) data on Permian and Triassic material, we present a first qualitative interpretation of relative depth patterns and the related functional prevalence (most deeply impressed area) within footprints. We identified three main groups: (1) anamniote, captorhinomorph/parareptile tracks (medialmedian functional prevalence), (2) diapsid tracks (median functional prevalence), and (3) synapsid tracks (median-lateral functional prevalence). The use of 3D photogrammetric models brings new light to the tetrapod footprint record, helping to better understand tetrapod communities throughout the late Paleozoic (and the end-Guadalupian and end-Permian extinctions) and the tetrapod recovery during the early Mesozoic.
... The link between footprints and their producers is of great interest in vertebrate ichnology and the usefulness for both stratigraphic and biological purposes depends in part on the precise assignment to the producing taxa (Lockley 1991(Lockley , 1998Manning 2004;Falkingham 2014). This interpretation presents a series of limitations of a sedimentary (e.g. ...
... substrate moisture content, sediment grain size, sediment time exposed, processes that may further modify the track, three dimensional preservation), anatomical (e.g. locomotory pattern, absence of synapomorphies in the autopodium), taxonomic (e.g impossibility to correlate a taxonomic level with an taxonomic one) and a stratigraphic nature showing that that a trace cannot always be assigned to a trackmaker despite its good conservation (Leonardi 1987;Carrano and Wilson 2001;Razzolini et al. 2014;Falkingham 2014). ...
Article
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In this work we present new avian fossil footprints preserved in the Vinchina Formation at del Yeso Creek, La Rioja, Argentina. To understand the morphological variation of very similar footprints not organizaed in trackways, we use statistical analyses combined with taphonomic analyses, resulting in a more refined classification of the ichnotaxa. Accordingly, the monospecific ichnogenus Phoenicopterichnum rector Aramayo and Manera de Blanco 1987 assigned to flamingoes, has two new ichnospecies, P. lucioi isp. nov. and P. vinchinaensis isp. nov. In addition, footprints produced by anatids, Anatipeda ips, are also reported. The predictive clustering analysis allow us to propose new ichnospe-cies by identifying which variables are of statistical significance to differentiate morphotypes. We defined two taphonomic groups and plotted it on the cluster analysis, inferring that the taphonomic input do not influence the morphologic analysis. Finally, we recommend testing statistically which variables are in fact of more influence in distinguishing morphotypes and/or ichnotaxa. That increase the value of paleobiological and/or ichnotaxonomical interpretations. By using these tools, we can achieve a better identification of footprint morphologies and consequently their trackmakers and the assignation of ichnotaxa to help address biological diversity in the past.
... Fossilised tracks are a valuable palaeontological resource providing direct insight into the lives of extinct organisms otherwise unavailable from bones alone. In the absence of body fossils, tracks can provide unique evidence of the producer's presence in the fauna at that time and setting, as well as information about limb motion, soft-tissue anatomy and palaeoenvironment (Padian and Olsen, 1984;Minter et al., 2007;Falkingham, 2014). To date, no terrestrial vertebrate trace fossils have been recorded from the Penarth Group of the Upper Triassic, including the Aust section (Swift and Duffin, 1999), nor indeed from any deposits in the UK dating to the Rhaetian (Sarjeant, 1975;Delair and Sarjeant, 1985), being the final division of the Triassic lasting from 205.7-201.3 ...
... This means that fleeting terrestrial conditions would not be so surprising. Although body fossil remains may be the result of post-mortem transportation, tracks must necessarily be preserved in situ providing certainty over environmental reconstruction (Conti et al., 2005;Falkingham, 2014). Specimen TECMAG0161 / Fig. 4. CT data presented as volume render and single slice, illustrating the lack of detail and structure visible beneath impression 1. Scale bar for lower slice = 100 mm. ...
Article
Terrestrial vertebrate trace fossils are relatively abundant in mid-to-late Triassic and early Jurassic deposits in the British Isles but to date none at all have been recorded from the Rhaetian, the final stage of the Triassic. This represents a persistent gap in the terrestrial ichnological record. We present the first Rhaetian track to be recognised in the British Isles, found at Aust Cliff on the south bank of the Severn Estuary near Bristol in SW England. This locality is well known for disarticulated remains of Rhaetian fossil reptiles including some terrestrial species but in 2006 a track (TECMAG0161) was found for the fist time. Although the specimen was found ex-situ the palynological data from the surrounding matrix confirms a Rhaetian age. The track was examined with CT scanning and photogrammetry. We tentatively assign the track to the ichnogenus Procolophonichnium based on size and digit proportions. The isolated nature of the specimen offers little concrete information about the track maker but such tracks have previously been attributed to parareptiles or therapsid trackmakers. The specimen adds a datapoint to an otherwise ichnologically empty period of time in the British Isles. The track also provides solid evidence for a [locally] terrestrial environment in a sequence that is otherwise considered predominantly marine or estuarine. This discovery suggests that there may be more such tetrapod tracks of Rhaetian age preserved, at least at Aust, and further searching will hopefully lead to the current minimal dataset being expanded.
... Numerous pieces of information can be gathered by comparing fossil trackways to modern trackways. The focus of many paleoichnological studies is locomotion and morphology, behavior, and/or paleoenvironmental conditions; these factors can be replicated in modern settings to help improve understanding of fossil data (e.g., Padian and Olsen 1989;Melchor et al. 2012;Falkingham 2014). Gait, stride length, and speed can be inferred from any trackway but not from body-fossil evidence alone. ...
... Gait, stride length, and speed can be inferred from any trackway but not from body-fossil evidence alone. Tracks are three-dimensional (3D) structures; track depth is important because understanding the forces needed to create the track, along with the relative depth of varying portions of the track, are critical for interpreting patterns of locomotion including speed or posture (e.g., Thulborn and Wade 1989;Gatesy et al. 1999;Avanzini et al. 2012;Xing et al. 2012;Falkingham 2014). As direct observation of extinct fossil tracemakers is impossible, the best way to interpret all of these features is to capture them in neoichnological studies that limit human presence when animals are producing tracks and trackways. ...
Article
A new experimental setup using a collapsible wooden tray, monopod, and digital video camera is used to observe and collect modern bird tracks. This setup is unique because it simultaneously captures tracemaker behavior, trace morphology, and media consistency (i.e., grain size and moisture content), and can be used in the laboratory and in natural environments. Here we provide examples produced by domestic chickens (Gallus gallus). Using this setup we determined that bird track morphology varies in a predictable manner with respect to sediment grain size and the percent of water present. The finer the sediment grain size, the more detail is likely to be preserved. If the sediment is completely dry, no track details will be preserved - digit impressions will be broad and will not taper at the tips; digit impression length will be longer than the actual digit lengths. If the sediment is wet (8.8%-6.7%), digit impressions will taper to points, will not be as wide as in dry sediment, and will not preserve pad impressions. If the sediment is variably moist (5.3%-3.2%), the detail level of pad or scale impressions, depending on the grain size, may be present. Within this study, we propose a sinuosity index that allows for quantification of sinuous avian trackways, and quantify the trackway parameters of behaviors, including start-stop walking, walking, running, takeoff, and landing. Both takeoff and landing traces are significantly deeper than the proceeding or following walking and running traces. Start-stop walking does not always result in side-by-side paired tracks, and often the bird will pause in midstride. Linking behavior and morphology of tracks can be used to better interpret ancient behavior and the depositional environment in which ancient tracks were produced.
... Vertebrate tracks are often ephemeral, but under exceptional circumstances these traces may become part of the fossil record. When preserved, these ichnological data can provide avenues for important paleobiological insights regarding extinct taxa, including those related to anatomy, locomotion, social behaviors, and paleoenvironments (see Falkingham, 2014 for a review). ...
Article
Hominin footprint sites are excellent sources of data that provide insights into early human physiology, anatomy, and social structures. They are also potential tourist attractions that are often situated in relatively under-developed parts of the world. Unfortunately, many footprint sites are also located in high energy environments and/or are pressed into poorly indurated sediments, which make them highly susceptible to erosion. This paper proposes a non-invasive and low-cost method employing Structure- from-Motion photogrammetry to quantify erosion rates in the absence of permanent ground control points. Using point cloud comparison algorithms between data collected at different times, it is possible to quantitatively analyze the locations, volumes, and rates of material loss. We applied this technique to several footprints within the Engare Sero footprint site in northern Tanzania to assess erosional change between 2010 and 2017. Our comparisons show that prints are vertically eroding at average rates ranging from 0.10 to 0.17 mm/yr with some localized areas experiencing much higher rates over shorter dura- tions. We identify three primary modes of erosion: 1) flaking, 2) abrasion, and 3) boring of holes. Erosion appears to have occurred episodically with major events, such as flooding, separated by periods of relative stability. The methods presented here are valuable for paleoanthropologists to better understand how footprint erosion might adversely affect inferences regarding print-makers, and they are valuable for decision-makers, who can create conservation plans to better protect and maximize the utility of known hominin footprint sites.
... In the 1980s, this palaeoecological research diverged into (1) ichnofabric analysis, which focused on tiering positions and crosscutting relations (e.g., Bromley and Ekdale 1986;Taylor and Goldring 1993) and (2) ichnofacies analysis, which focused on ethological treatments (e.g., Bromley, Pemberton, and Rahmani 1984;Pemberton and Frey 1984;Frey, Pemberton, and Saunders 1990;Bromley and Asgaard 1991). The concepts in ichnology advanced further with neoichnological experimental surveys (e.g., Gingras et al. 2008;Counts and Hasiotis 2009;Knecht et al. 2009;Rodr ıguez-Tovar et al. 2010;Falkingham 2014) which improved in interpreting the origin of the trace fossils and also with the advancements in trace fossil's application in sequence stratigraphy (e.g., Savrda 1991;Buatois and M angano 2009); petroleum exploration (e.g., Pemberton et al. 1992b;La Croix et al. 2017) and evolutionary studies (e.g., Buatois and M angano 2013). ...
Article
Jurassic deposits of shallow to marginal marine (delta) environments are widely reported from different continents of the world. This study shows inter-relationship of the animal-sediment behaviours in shallow and marginal marine conditions, suggesting an interpretation of the possible ichnodisparity. The Jurassic succession exposed at Washtawa Dome and Adhoi Anticline of Wagad highland, Kachchh comprises an approximately 341 m thick succession, divided into two formations – Lower Washtawa and Upper Wagad Sandstone. Eight sparsely to highly bioturbated sedimentary units show twenty-three identifiable ichnospecies from fifteen ichnogenera representing five ichnoassemblages broadly attributable to the Skolithos and the Cruziana ichnofacies, and developed in shallow-marine strandplain shoreface and delta depositional facies. The relative frequency statistical data reveals the dominant occurrence of feeding structures generated by polychaetes preferentially in quartz arenites. These structures represent sub-horizontal, sub-vertical and complex burrows, and show twelve and six categories of architectural designing Callovian-Oxfordian of shallow-marine shoreface and Oxfordian-Kimmeridgian shallow-water delta successions, respectively. The lower ichnodiversity and ichnodisparity associated with the Oxfordian-Kimmeridgian deltaic intervals represents a decrease in the exploitation of under-used ecospace, due to unfavourable environmental conditions rather than an expression of evolutionary radiation.
... The phase of track registration is a dynamic interaction between the living producer and the substrate, and so the producer's foot anatomy and behavior and the substrate properties at the time of impression play a central role in this phase (e.g. Padian and Olsen, 1984;Milàn and Bromley, 2006;Milan and Bromley, 2007;Falkingham, 2014;Farlow et al., 2018a). Usually, the footprints start to be registered in their proximal part (sole, palm, proximal part of digits), which act as a support during the foot's landing, and they end to be registered in their distal part (distal part of digits, claws), which act as a lever for the foot propulsion (e.g. ...
Article
The morphology of fossil footprints is the basis of vertebrate footprint ichnology. However, the processes acting during and after trace fossil registration which are responsible for the final morphology have never been precisely defined, resulting in a dearth of nomenclature. Therefore, we discuss the concepts of ichnotaphonomy, ichnostratinomy, taphonomy, biostratinomy, registration and diagenesis and describe the processes acting on footprint morphology. In order to evaluate the morphological quality of tetrapod footprints, we introduce the concept of morphological preservation, which is related to the morphological quality of footprints (M-preservation, acronym MP), and distinguish it from physical preservation (P-preservation, acronym PP), which characterizes whether or not a track is eliminated by taphonomic and diagenetic processes. M-preservation includes all the morphological features produced during and after track registration prior to its study, and may be divided into substages (ichnostratinomic, registrational, taphonomic, stratinomic, diagenetic). Moreover, we propose an updated numerical preservation scale for M-preservation. It ranges from 0.0 (worst preservation) to 3.0 (best preservation); intermediate values may be used and specific features may be indicated by letters. In vertebrate footprint ichnotaxonomy, we regard the anatomy-consistent morphology and to a lesser extent the trackway pattern as the only acceptable ichnotaxobases. Only footprints showing a good morphological preservation (grade 2.0–3.0) are useful in ichnotaxonomy, whereas ichnotaxa based on poor morphological preservation (grade 0.0–1.5) are considered ichnotaphotaxa (nomina dubia) characterized by extramorphologies. We applied the preservation scale on examples from the Palaeozoic to the present time, including three ichnotaphotaxa and 18 anatomy-consistent ichnotaxa/morphotypes attributed to several vertebrate footprint producers. Results indicate the utility, feasibility and suitability of this method for the entire vertebrate footprint record in any lithofacies, strongly recommending its use in future ichnotaxonomic studies.
... They also remove trackway asymmetries, including discrepancies between left and right pace lengths, and lateral displacements of the manual relative to the pedal prints. The morphology of fossil footprints is controlled by three factors, namely, the anatomy of the trackmaker, substrate properties, and behavior (Falkingham, 2014). This concept may be extended to trackway configurations. ...
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Forelimb posture in sauropod dinosaurs is still poorly understood. Although a laterally directed (semisupinated) manus is the plesiomorphic condition in sauropodomorphs, the sauropod track record prevailingly shows anterolateral to anterior manus orientations, suggesting a high degree of manus pronation. The ?Middle Jurassic Tafaytour tracksites described herein preserve at least 10 trackways, nine of which show laterally oriented, and in two examples even posterolaterally oriented, manual impressions. Located in the Argana Basin of the Western High Atlas, Morocco, the tracksite yields hundreds of footprints on a highly bioturbated surface, including examples with well-preserved digit and claw impressions. Footprint morphology and trackway configuration vary greatly between trackways. A literature review indicates that laterally directed manual impressions are restricted to small- and medium-sized trackmakers. Statistical analysis was performed on a larger sample (n = 79) of small sauropod trackways from around the world, indicating that lateral manual orientations are correlated with low locomotion speeds and narrow trackway gauges. Manus pronation in sauropods is hypothesized to occur when the forelimb is actively contributing to the propulsion of the animal, which would be the case at faster speeds or at wider trackway gauges where the center of mass is located more anteriorly. We present new approaches to the quantitative analysis of trackway data. Mean configuration plots allow for direct graphical comparisons of different trackways. Two types of trackway asymmetries are defined and quantified. The apparent glenoacetabular distance (GAD) represents a feasible proxy for body size, at least for the smaller sauropod trackmakers analyzed herein. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Lallensack, J. N., S. Ishigaki, A. Lagnaoui, M. Buchwitz, and O. Wings. 2019. Forelimb orientation and locomotion of sauropod dinosaurs: insights from the ?Middle Jurassic Tafaytour tracksites (Argana Basin, Morocco). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1512501.
... Ichnoassemblages of dinosaur footprints shed light on the diversity and community structure of their tracemakers (Lockley, 1989;Falkingham, 2014), but their form and abundance is often biased by the composition and sedimentary mechanics of the substrate onto which they were emplaced, as well as the outcrop of strata in which they are preserved (Milàn and Bromley, 2007;Falkingham et al., 2011;Gatesy and Falkingham, 2017). ...
Article
An assemblage of dinosaur footprints is reported from the Lower Cretaceous (Berriasian-Valanginian) Ashdown Formation of East Sussex, southern England. The ichnofauna is concentrated around a 2 m thick stratigraphic marker, the Lee Ness Sandstone, where recent cliff retreat has revealed 85 recognisable footprints attributable to 13 morphotypes, many of which bear high-fidelity skin impressions. The newly identified morphotypes mean that this tracksite hosts one of the most diverse dinosaur ichnoassemblages in the well-documented Mesozoic record of Britain; recording the activity of theropod, ornithopod, thyreophoran and possibly sauropod tracemakers. Most of the footprints were emplaced on a single floodplain mudstone horizon beneath a fluvial crevasse splay sandstone, where preservation was favoured by cohesive sediment and a prolonged interval of sedimentary stasis, during which trackways could be imparted. The sedimentological context of the trackways reveals evidence of interactions between dinosaurs and the riverine landscape that they inhabited; including the development of microtopographies around footprints, which impacted invertebrate burrowing activity, and evidence for dinosaur wading below the bankfull level of small meandering channels and oxbow lakes. Modern analogue suggests that the large dinosaurs may have played a significant role as zoogeomorphic engineers within the ancient floodplain setting, but the imperfect translation of sedimentary environment to sedimentary rock means that geological evidence for such is ambiguous.
... Longer histories of ichnological research in other subfields of paleontology have demonstrated the variety of ways in which tracks can offer valuable insights into the anatomy, locomotion, ecology, and behavior of fossil taxa (e.g., Hitchcock, 1836;Lockley and Meyer, 2000;Falkingham, 2014). In many ways, these immediate snapshots of behavior, which are typically formed in quick succession by ani- mals that presumably lived in close proximity and potentially interacted with each other, provide windows to the past that are unparalleled in the skeletal fossil record. ...
Article
Recent discoveries have made hominin tracks an increasingly prevalent component of the human fossil record, and these data have the capacity to inform long-standing debates regarding the biomechanics of hominin locomotion. However, there is currently no consensus on how to decipher biomechanical variables from hominin tracks. These debates can be linked to our generally limited understanding of the complex interactions between anatomy, motion, and substrate that give rise to track morphology. These interactions are difficult to study because direct visualization of the track formation process is impeded by foot and substrate opacity. To address these obstacles, we developed biplanar X-ray and computer animation methods, derived from X-ray Reconstruction of Moving Morphology (XROMM), to analyze the 3D dynamics of three human subjects' feet as they walked across four substrates (three deformable muds and rigid composite panel). By imaging and reconstructing 3D positions of external markers, we quantified the 3D dynamics at the foot-substrate interface. Foot shape, specifically heel and medial longitudinal arch deformation, was significantly affected by substrate rigidity. In deformable muds, we found that depths measured across tracks did not directly reflect the motions of the corresponding regions of the foot, and that track outlines were not perfectly representative of foot size. These results highlight the complex, dynamic nature of track formation, and the experimental methods presented here offer a promising avenue for developing and refining methods for accurately inferring foot anatomy and gait biomechanics from fossil hominin tracks.
... The formation of an ichnite is the result of a complex interaction between the autopode and the substrate. The track morphology is not only determined by the podal anatomy, but also depends on extrinsic agents such as the trackmaker behavior (e.g., foot pressure, speed, motion, gait type), the nature of the track-bearer deposits (e.g., composition, granulometry, moisture content, degree of consistency, infaunal activity), and properties of the fluid/sediment interface (e.g., subaerial and/or subaquatic environment, flow energy, weathering intensity, sedimentation and erosion rates, presence of superficial microbial mat, development of a vegetal cover) (Minter et al., 2007;Falkingham, 2014;Falkingham et al., 2014;McCrea et al., 2015). Therefore, there is a great number of external factors, either syn-or post-depositional (Schulp and Brokx, 1999;Schulp, 2002), as well as a series of pre-and post-impressional effects (McCrea et al., 2015), that can actively influence the footprint appearance and trackway quality, and that must be properly recognized and systematically excluded from the diagnosis of the ichnotaxon. ...
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The analysis of paleoichnites and trackways corresponding to Holarctic ungulates, from the late Pleistocene (Lujanian Stage/Age) of Pehuen Co and Laguna del Monte tracksites (Buenos Aires Province, Argentina), allows the recognition of several clinical signs (ich-nopathologies) that reflect some of the main pedal affections and alterations experienced by living members of the group. Proboscipeda australis (Aramayo and Manera de Bianco, 1987a) presents occasional fissures on its hoof-prints, interpreted as fractures on the hornwall (vertical) and cracking of the sole (horizontal). Hippipeda isp. exhibits a series of morphologic anomalies in the digital impression, linked to contracted heel (transversely compressed hoof, narrowing and distal projection of tal-onar region, with an approximation of both heel-bulb impressions and an enlargement of the spacing between frog baseline and heel buttresses), distorted hoof (asymmetrical sole region and hoof wall, with forwardly projected internal pillar [toe-quarter junction] and anteriorly displaced external heel buttress), turkish-slipper foot (over-elongated hoofprint, showing hyper-lengthening of lateral walls [inner and outer quarters], and hypertrophy of frog and bars). Lamaichnum guanicoe Aramayo and Manera de Bianco, 1987b displays eventual evidence of horny overgrowth: inward/ subparallel (loss of bilateral symmetry, medial curving of digits, uneven sizing of toepad prints) and outward/divergent (lateral curving of digits, overexpansion of interclavular gap [with ample separation between both digital ends], enlargement and widening of the tracks, normal acquisition of a secondary heteropody). These intraspecific variations (ichnopathological characters) are often used to segregate a second llamoid ichnospecies: Lamaichnum tulipensis (Aramayo and Manera de Bianco, 1987b), herein proposed as teratologic synonym of Lamaichnum guanicoe.
... Substrate consistency depends on its rheology and mechanics and varies with the texture (i.e., size, sorting, sphericity, roundness, etc.) of the sand grains, the mineralogical composition of the clasts and the moisture, but other conditions also affect track preservation in an eolian setting, such as the rapid burial of the perturbed sediment, the dip angle of the substrate, and the moisture content at the exact moment of the production of the tracks (McKee, 1944(McKee, , 1947Allen, 1997;Manning, 2004;Milàn, 2006;Milàn & Bromley, 2006;Jackson, Whyte & Romano, 2009;Jackson, Whyte & Romano, 2010;Scott, Renaut & Owen, 2010;Razzolini et al., 2014;Mancuso et al., 2016;Milàn & Falkingham, 2016). Biological (such as the animal's mass, limb dynamics and the geometry of the autopodia) and ecological (such as the trackmaker's speed and direction of the travel) variations are also known to affect the preservation of tetrapod tracks (Thulborn, 1990;Falkingham, Margetts & Manning, 2010;Falkingham et al., 2011;Falkingham, 2014;Falkingham, Hage & Bäker, 2014). ...
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Tetrapod tracks in eolianites are widespread in the fossil record since the late Paleozoic. Among these ichnofaunas, the ichnogenus Chelichnus is the most representative of the Permian tetrapod ichnological record of eolian deposits of Europe, North America and South America, where the Chelichnus Ichnofacies often occurs. In this contribution, we describe five sets of tracks (one of which is preserved in cross-section), representing the first occurrence of Dicynodontipus and Chelichnus in the “Pirambóia Formation” of southern Brazil. This unit represents a humid desert in southwestern Pangea and its lower and upper contacts lead us to consider its age as Lopingian–Induan. The five sets of tracks studied were compared with several ichnotaxa and body fossils with appendicular elements preserved, allowing us to attribute these tracks to dicynodonts and other indeterminate therapsids. Even though the “Pirambóia Formation” track record is sparse and sub-optimally preserved, it is an important key to better understand the occupation of arid environments by tetrapods across the Permo–Triassic boundary.
... The fossilized tracks and trackways of extinct vertebrates offer valuable information about locomotion, behaviour, palaeoecology, substrate conditions, and paleoenvironment 5,6 . Indeed, fossil tracks can also complement information from the osteological record by providing additional data on geographical distributions 7 , first and last occurrences 7,8 and evolutionary radiations 9 . ...
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We present a new locality with at least 880 vertebrate tracks found at the top of a limestone bed from the lower Miocene Tudela Formation (Spain). The trampled surface was formed by artiodactyls that crossed a muddy carbonate accumulated under the influence of water level variations in a palustrine environment. The tracks reflect different types of morphological preservation. The well-preserved tracks have tetradactyl digit impressions caused by both manus and pes, and are the type series of a new artiodactyl ichnotaxon, Fustinianapodus arriazui ichnogen. nov. and ichnosp. nov. The rest of the tracks, which are not as well preserved, are didactyl and were classified as undetermined artiodactyl tracks. According to their preservation, morphology, size, arrangement and orientation, we propose that this tracksite is the product of a social behaviour, particularly gregariousness, of a multi-age group of artiodactyls ~19 Ma ago. The morphologic and palaeoecologic data presented here suggest that the trackmakers were a group of anthracotheres with a livelihood similar to current hippos. They crossed, periodically, a fresh water palustrine area along some preferential pathways (trails).
... The final shape of a footprint is determined by a combination of factors related to the anatomy of the trackmaker's autopodium, the kinematics and the substrate (Marty, Strasser & Meyer, 2009;Falkingham, 2014); another important factor is the level in which the tracks were preserved (Milàn & Bromley, 2006), i.e., if they are preserved as undertracks. In the case of the tracksites of Highway A16, we can rule out this factor as the excavations were carried out level-by-level, so the footprints are true tracks (or natural casts). ...
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Background Minute to medium-sized (footprint length (FL) less than 30 cm) tridactyl dinosaur tracks are the most abundant in the Late Jurassic tracksites of Highway A16 (Reuchenette Formation, Kimmeridgian) in the Jura Mountains (NW Switzerland). During excavations, two morphotypes, one gracile and one robust, were identified in the field. Furthermore, two large-sized theropod ichnospecies ( Megalosauripus transjuranicus and Jurabrontes curtedulensis ) and an ornithopod-like morphotype (Morphotype II) have recently been described at these sites. Methods The quality of morphological preservation (preservation grade), the depth of the footprint, the shape variation, and the footprint proportions (FL/footprint width (FW) ratio and mesaxony) along the trackways have been analyzed using 3D models and false-color depth maps in order to determine the exact number of small to medium-sized morphotypes present in the tracksites. Results The study of footprints ( n = 93) recovered during the excavations has made it possible to identify and characterize the two morphotypes distinguished in the field. The gracile morphotype is mainly characterized by a high FL/FW ratio, high mesaxony, low divarication angles and clear, sharp claw marks, and phalangeal pads (2-3-4). By contrast, the robust morphotype is characterized by a lower FL/FW ratio, weaker mesaxony, slightly higher divarication angles and clear, sharp claw marks (when preserved), whereas the phalangeal pads are not clearly preserved although they might be present. Discussion The analysis does not allow the two morphotypes to be associated within the same morphological continuum. Thus, they cannot be extramorphological variations of similar tracks produced by a single trackmaker. Comparison of the two morphotypes with the larger morphotypes described in the formation ( M. transjuranicus , J. curtedulensis , and Morphotype II) and the spatio-temporal relationships of the trackways suggest that the smaller morphotypes cannot reliably be considered as small individuals of any of the larger morphotypes. The morphometric data of some specimens of the robust morphotype (even lower values for the length/width ratio and mesaxony) suggest that more than one ichnotaxon might be represented within the robust morphotype. The features of the gracile morphotype (cf. Kalohipus isp.) are typical of “grallatorid” ichnotaxa with low mesaxony whereas those of the robust morphotype (cf. Therangospodus isp. and Therangospodus ? isp.) are reminiscent of Therangospodus pandemicus . This work sheds new light on combining an analysis of variations in footprint morphology through 3D models and false-color depth maps, with the study of possible ontogenetic variations and the identification of small-sized tridactyl ichnotaxa for the description of new dinosaur tracks.
... The reader may be forgiven for questioning at the outset, however, what dinosaur and human tracks have in common and why they appear together in the same work. Even though such tracks are imprinted by completely different trackmakers and in very different geological time periods, both are biogenic sedimentary structures that represent the dynamic interaction of a foot (morphology + kinematics) with the substrate properties at the time of formation (Padian & Olsen, 1984;Marty, Strasser & Meyer, 2009;Falkingham, 2014). Once formed they may be affected and modified during taphonomy (e.g., Cohen et al., 1991;Scott et al., 2007;Marty, Strasser & Meyer, 2009;Scott, Renaut & Owen, 2010) and diagenesis (Phillips et al., 2007). ...
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Vertebrate tracks are subject to a wide distribution of morphological types. A single trackmaker may be associated with a range of tracks reflecting individual pedal anatomy and behavioural kinematics mediated through substrate properties which may vary both in space and time. Accordingly, the same trackmaker can leave substantially different morphotypes something which must be considered in creating ichnotaxa. In modern practice this is often captured by the collection of a series of 3D track models. We introduce two concepts to help integrate these 3D models into ichnological analysis procedures. The mediotype is based on the idea of using statistically-generated three-dimensional track models (median or mean) of the type specimens to create a composite track to support formal recognition of a ichno type. A representative track (mean and/or median) is created from a set of individual reference tracks or from multiple examples from one or more trackways. In contrast, stat-tracks refer to other digitally generated tracks which may explore variance. For example, they are useful in: understanding the preservation variability of a given track sample; identifying characteristics or unusual track features; or simply as a quantitative comparison tool. Both concepts assist in making ichnotaxonomical interpretations and we argue that they should become part of the standard procedure when instituting new ichnotaxa. As three-dimensional models start to become a standard in publications on vertebrate ichnology, the mediotype and stat-track concepts have the potential to help guiding a revolution in the study of vertebrate ichnology and ichnotaxonomy.
... Although the incorporation of additional body parts, such as the tail or torso, into a musculoskeletal model may further constrain limb ROM, this must be balanced against a concurrent increase in uncertainty regarding model articulation and also the concomitant reduction in analytical sample size, which becomes limited perforce to those specimens that are relatively complete. On the rare occasions when trackways can be assigned confidently to fossil taxa, their gauge, stride length, and other track features may also inform potential posture and limb range of motion (e.g., Alexander, 1989;Henderson, 2006;Hatala et al., 2016; but see Falkingham, 2014). ...
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The moment arm of a muscle defines its leverage around a given joint. In a clinical setting, the quantification of muscle moment arms is an important means of establishing the ‘healthy’ functioning of a muscle and in identifying and treating musculoskeletal abnormalities. Elsewhere in modern animal taxa, moment arm studies aim to illuminate adaptions of the musculoskeletal system towards particular locomotor or feeding behaviors. In the absence of kinematic data, paleontologists have likewise relied upon estimated muscle moment arms as a means of reconstructing musculoskeletal function and biomechanical performance in fossil species. With the application of ‘virtual paleontological’ techniques, it is possible to generate increasingly detailed musculoskeletal models of extinct taxa. However, the steps taken to derive such models of complex systems are seldom reported in detail. Here we present a case study for calculating three-dimensional muscle moment arms using Stegosaurus stenops Marsh, 1887, to highlight both the potential and the limitations of this approach in vertebrate paleontology. We find the technique to be mostly insensitive to choices in muscle modeling parameters (particularly relative to other sources of uncertainty in paleontological studies), although exceptions do exist. Of more concern is the current lack of consensus on what functional signals, if any, are contained within moment arm data derived from extant species. Until a correlation between muscle moment arm and function can be broadly identified across a range of modern taxa, the interpretation of moment arms calculated for extinct taxa should be approached with caution. Citation for this article: Brassey, C. A., S. C. R. Maidment, and P. M. Barrett. 2017. Muscle moment arm analyses applied to vertebrate paleontology: a case study using Stegosaurus stenops Marsh, 1887. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1361432.
... Because the vertebrate track morphology is determined by the limb motion, autopod anatomy and substrate consistency, studies about fossil tracks provide information about trackmaker, behaviour and palaeoenvironment (see Falkingham, 2014). Therefore, when vertebrate tracks and trackways are well-preserved, it is possible to obtain more valuable information about the autopod morphology and the trackmaker mode of locomotion (Gatesy, 2001;Castanera et al., 2013a,b;Razzolini et al., 2016). ...
Article
The Paso Córdoba fossiliferous site (Río Negro, Northern Patagonia) is one of the first Mesozoic fossiliferous localities studied in Argentina. There, turtle, crocodile and dinosaur remains as well as dinosaur and bird tracks have been recorded. Recently, a new locality with vertebrate tracks, the Cañadón del Desvío, has been discovered in Paso Córdoba. Six track-bearing layers were located in outcrops belonging to the Anacleto (lower to middle Campanian, Neuquén Group) and Allen (middle Campanian-lower Maastrichtian, Malargüe Group) formations. The Cañadón del Desvío locality reveals that vertebrate trace fossils are distributed in two distinct environments, floodplains of a meandering fluvial to shallow lacustrine system and a wet interdune deposit that is associated to an aeolian setting. Also, in the logged section several soft sediment deformation structures were found. In regard of this, a sedimentary facies analysis is provided in order to assess the palaeoenvironmental implications of this new record. The analysed tracks are preserved in cross-sections, on bedding-planes and as natural casts. When it is possible, the tracking surface, true tracks, undertracks and overtracks/natural casts have been identified and the track preservation and the formation history of the tracksite are discussed. Only two tracks preserve enough anatomical details to relate them with their trackmakers, in this case hadrosaurid dinosaurs. The stratigraphical, facial and palaeoenvironmental data of this study support the idea of a transitional passage between the Anacleto and Allen Formation in Paso Córdoba. The presence of hadrosaurid dinosaur tracks suggests that the upper part of the log, where this kind of tracks were found, likely belong to Allen Formation due to this dinosaurs appear in the Southern Hemisphere in this epoch. The sum of osteological and ichnological remains improve the Paso Córdoba paleofaunistic knowledge. The presence of six different levels in which the trackmakers walked reflects the abundance of vertebrates in the transition between Anacleto and Allen formations.
... transjuranicus open nomenclature is used when tracks reflect a limited preservational variation on the strict definition of this ichnogenus [3] and therefore when digits are separated and distinguishable from one another, heel pad (PIV1) is not very discernible, and morphometric parameters for tracks and trackway configuration are typical, such as tracks longer than wide, elongated, asymmetric, moderate mesaxony, notch developed between digit II and heel area impression, trackway configuration somewhat irregular. This classification is linked to a preservational variation of the M. transjuranicus track morphology due to substrate consistency, limb kinematics and/or behavior of the trackmaker [101] rather than foot anatomy (different trackmaker). ...
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A new ichnospecies of a large theropod dinosaur, Megalosauripus transjuranicus, is described from the Reuchenette Formation (Early–Late Kimmeridgian, Late Jurassic) of NW Switzerland. It is based on very well-preserved and morphologically-distinct tracks (impressions) and several trackways, including different preservational types from different tracksites and horizons. All trackways were excavated along federal Highway A16 near Courtedoux (Canton Jura) and systematically documented in the field including orthophotos and laserscans. The best-preserved tracks were recovered and additional tracks were casted. Megalosauripus transjuranicus is characterized by tridactyl tracks with clear claw and digital pad impressions, and notably an exceptionally large and round first phalangeal pad on the fourth digit (PIV1) that is connected to digit IV and forms the round heel area. Due to this combination of features, M. transjuranicus clearly is of theropod (and not ornitho-pod) origin. M. transjuranicus is compared to other Megalosauripus tracks and similar ichno-taxa and other unassigned tracks from the Early Jurassic to Early Cretaceous. It is clearly different from other ichnogenera assigned to large theropods such as Eubrontes–Grallator from the Late Triassic and Early Jurassic or Megalosauripus–Megalosauropus–Bueckebur-gichnus and Therangospodus tracks from the Late Jurassic and Early Cretaceous. A second tridactyl morphotype (called Morphotype II) is different from Megalosauripus trans-juranicus in being subsymmetric, longer than wide (sometimes almost as wide as long), with blunt toe impressions and no evidence for discrete phalangeal pad and claw marks. Some Morphotype II tracks are found in trackways that are assigned to M. transjuranicus, to M.? transjuranicus or M. cf. transjuranicus indicating that some Morphotype II tracks are intra-trackway preservational variants of a morphological continuum of Megalosauripus transjura-nicus. On the other hand, several up to 40 steps long trackways very consistently present Morphotype II features (notably blunt digits) and do not exhibit any of the features that are typical for Megalosauripus (notably phalangeal pads). Therefore, it is not very likely that these tracks are preservational variants of Megalosauripus transjuranicus or PLOS ONE | https://doi.
... Various methods have been developed to analyze the morphology of theropod footprints formed in a variety of sediments with varying fluidity levels, effects of movement including speed and effects on underlying sedimentary layers (e.g., Falkingham, 2014;Falkingham, 2016;Falkingham & Gatesy, 2014;Lallensack, Van-Heteren & Wings, 2016;Milàn & Bromley, 2006;Milàn, 2006). One of the more novel approaches was utilizing live Dromaius (emus) to walk through sediments of varying grain sizes and fluidity levels; which demonstrated that morphological variation of the prints were dictated by variations of substrate consistency (Milàn, 2006). ...
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Distinguishing the difference between theropod and ornithopod footprints has proved a difficult task due to their similarities. Herein our aim was to produce a method where a skeleton could be more closely matched to actual fossilised footprints. The reconstructed pes of the Australian Megaraptoran Australovenator wintonensis was utilised for this footprint reconstruction. It was 3-D printed in life size, molded and cast to produce a flexible theropod foot for footprint creation. The Dinosaur Stampede National Monument, Lark Quarry, Queensland, Australia was used as our case study to compare fossilised dinosaur footprints with our reconstructed theropod prints. The footprints were created in a sediment that resembled the paleo-sediments of Lark Quarry prior to being traversed by dinosaurs. Measurements of our Australovenator prints with two distinctly different print types at Lark Quarry revealed similarities with one distinct trackway which has been the center of recent debate. These footprints consist of 11 consecutive footprints and show distinct similarities in both size and proportions to our Australovenator footprints.
... These different infillings correspond both to internal overtracks but with a different preservation (see Marty et al., 2009 for further insights on internal overtracks). Such features suggest that the infilling occurred under slightly different environmental conditions, and thus that the surface was exposed (either under subaquatic or subaerial conditions, not covered by sediment) during a relatively long time (i.e., time averaged substrates; see Falkingham, 2014). Nonetheless, the lack of wrinkle structures within the microbial mat is indicative of a short time, if any, of exposition of the substrate under subaerial conditions. ...
Article
Triassic temnospondyl amphibian tracks are relatively rare, in contrast with the body fossil record. Herein we report temnospondyl tracks from the base of the Anthrakonitbank carbonate bed, within the upper Middle Triassic Lower Keuper succession (Erfurt Formation) in the Vellberg Fossil-Lagerstätte of southern Germany. The sedimentary succession comprises restricted marine deposits, and the track-bearing layer includes microbial mats covering thin bone-beds. The ichnological material includes >20 footprints, four of which are arranged in a trackway, and all footprints comprise manus impressions with no pes preserved. The combination of characters, such as tetradactyl clawless manus impressions, relative digit length and angulation, and trackway with low pace angulation, are different from any known tetrapod ichnotaxon. While the scarcity of material precludes a confident ichnotaxonomy, comparison with the autopodia in the body fossil record suggests capitosaur stereospondyls as the most probable trackmakers. Ichnological and sedimentological features indicate that the trackmakers displayed a walking-swimming locomotion, with a sprawling posture, only touching the substrate with the forelimbs, as seen in present-day swimming crocodiles. The Vellberg tetrapod tracks reported here contribute to our knowledge of the Triassic ichnological record, as well as the life style and habitats of temnospondyls.
... It has to be stressed that the shape of a track is not only determined by anatomy but also by foot kinematics and substrate properties (especially the water content), post-formational alteration, and the mode of preservation (e.g. transmitted undertrack vs. true track) (Falkingham 2014). For example, collapse of track walls may not only erase such detail but greatly shrink an impression and even lead to unexpected shapes Gatesy and Falkingham 2020;Lallensack et al. 2022b). ...
... On deformable substrates, however, the ground yields with each step. If the substrate deforms plastically (i.e., the deformation is not elastically recovered), a footprint, or track, is made (Allen, 1989;Falkingham et al., 2011;Falkingham, 2014). Previous studies have revealed that with increasing substrate deformability, greater subsurface foot motions occur, and increasingly larger volumes of substrate are impacted (Milàn, 2006;Hatala et al., 2018;Gatesy and Falkingham, 2020;. ...
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The stance phase of walking is when forces are applied to the environment to support, propel, and maneuver the body. Unlike solid surfaces, deformable substrates yield under load, allowing the foot to sink to varying degrees. For bipedal birds and their dinosaurian ancestors, a shared response to walking on these substrates has been identified in the looping path the digits follow underground. Because a volume of substrate preserves a 3-D record of stance phase in the form of footprints or tracks, understanding how the bipedal stride cycle relates to this looping motion is critical for building a track-based framework for the study of walking in extinct taxa. Here we used biplanar X-ray imaging to record and analyze 161 stance phases from 81 trials of three Helmeted Guineafowl (Numida meleagris) walking on radiolucent substrates of different consistency (solid, dry granular, firm to semi-liquid muds). Across all substrates, the feet sank to a range of depths up to 78% of hip height. With increasing substrate hydration, the majority of foot motion shifted from above to below ground. Walking kinematics sampled across all stride cycles revealed six sequential gait-based events originating from both feet, conserved throughout the spectrum of substrate consistencies during normal alternating walking. On all substrates that yielded, five sub-phases of gait were drawn out in space and formed a loop of varying shape. We describe the two-footed coordination and weight distribution that likely contributed to the observed looping patterns of an individual foot. Given such complex subsurface foot motion during normal alternating walking and some atypical walking behaviors, we discuss the definition of “stance phase” on deformable substrates. We also discuss implications of the gait-based origins of subsurface looping on the interpretation of locomotory information preserved in fossil dinosaur tracks.
... The high quality of most footprints would be enhanced by the presence of microbial mats (e.g., Marty et al., 2009;Carmona et al., 2011;Marchetti et al., 2019b). The high abundance of footprints, moreover, may have resulted from a combination of: (1) increased activity of the trackmakers (i.e., environment favourable for their presence), implying that the trackmakers would be gregarious as suggested by Demathieu and Demathieu (2004) (see also Diedrich, 2008;Mujal et al., 2016bMujal et al., , 2018a; (2) high preservation potential because of the presence of microbial mats, implying a potential overrepresentation of trackmakers in cohesive substrates exposed during a relatively long period (i.e., time averaging of substrates, see Falkingham, 2014). An additional explanation for the abundance of Rhynchosauroides is that this ichnogenus was probably produced by several different small-to medium-sized "lacertoid-like" taxa (neodiapsids, including archosauromorphs and lepidosauromorphs), which would have been common inhabitants of the Middle Triassic coastal settings (cf. ...
Article
Tetrapod ichnology is a powerful tool to reconstruct the faunal composition of Middle Triassic ecosystems. However, reconstructions based on a single palaeoenvironment provide an incomplete and impoverished picture of the actual palaeodiversity. In this paper, we analyse Middle Triassic tetrapod ichnoassociations from the detrital Muschelkalk facies of the Catalan Basin of northeast Spain, ranging from terrestrial to coastal settings. We identified two main tetrapod ichnoassociations, preserved in two different palaeoenvironments, comprising the following ichnogenera and morphotypes: Procolophonichnium, Chelonipus, Rhynchosauroides, Rotodactylus, Chirotherium, Isochirotherium, Sphingopus, and indeterminate chirotheriids. We also statistically analyse a database of all known Middle Triassic tetrapod footprint localities worldwide; this database includes, for each track locality, the precise age, the palaeoenvironment and the presence/absence of ichnotaxa. Our results on the composition of ichnofauna within the palaeoenvironments of the Catalan Basin are integrated into this database. This approach allows us to revisit the palaeoenvironmental bias linked to the marine transgression that affected the Western Tethys region. Tetrapod ichnoassociations reveal the following palaeoenvironmental patterns: (1) in coastal settings, ichnoassociations are Rhynchosauroides-dominated and diversity is relatively low; (2) in terrestrial settings and those with less marine influences, ichnoassociations are non-Rhynchosauroides-dominated, usually characterised by more abundant chirotheriid tracks and, generally, a higher track diversity. The correlation between tetrapod ichnoassociations and sedimentary facies reveals how palaeoenvironmental constraints influenced faunal assemblages, especially those of the Middle Triassic of the Western Tethys region. Ichnoassociations allow the ecological response of tetrapod faunas to the environmental changes to be inferred for this critical time interval. Marine transgressions strongly influenced tetrapod ecosystems: environmental conditions were key for the faunal recovery in the aftermath of the end-Permian extinction, with the settlement of the so-called modern faunas and the rise of the dinosaur lineage.
... While the importance of tracks as paleobiological data sources cannot be overstated, their interpretation suffers from multiple levels of uncertainty, including time averaging of tracksites, trackmaker identification, and interpretation of track morphology and trackway patterns. 20 Limb phase, as a central parameter, is important not only in its own right but may help to better constrain other uncertainties, such as duty factor and-because the apparent gleno-acetabular distance depends on the limb phase-body size and shape of the trackmaker, which may eventually aid in identifying trackmaker taxa. ...
Article
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Limb phase, the timing of the footfalls in quadrupedal locomotion that describes common gaits such as the trot and the pace gait,1,2 is widely believed to be difficult or even impossible to estimate for extinct tetrapods.3-5 We here present a fundamentally new approach that allows for estimating limb phase based on variation patterns in long trackways. The approach is tested on trackways of modern mammals, where the estimates generally correspond well with the actually employed limb phase. We then estimate limb phases of giant wide-gauged sauropod dinosaurs based on three long trackways from the Lower Cretaceous of Arkansas, US.6,7 Gait selection at the largest body sizes is of considerable interest given the lack of modern analogs. Contrary to previous assumptions,8,9 our estimates suggest lateral sequence diagonal couplet walks, in which the footfalls of the diagonal limb pairs (e.g., right hind and left fore) are more closely related in time than those of the same side of the body (e.g., right hind and right fore). Such a gait selection allows for efficient walking while maintaining diagonal limb support throughout the step cycle, which is important for a giant, wide-gauged trackmaker.10 Estimations of limb phase may help to constrain other gait parameters, body size and shape, and, finally, potential trackmaker taxa.
... All theropod tracks still appear to belong to a single type, with all the observable morphological variation (presence/absence of metatarsal impressions, variation in width of individual digits) being attributable to substrate conditions and animal behaviour (e.g. Marty et al. 2009;Falkingham 2014;Razzolini et al. 2014;Gatesy and Falkingham 2017;Heredia et al. 2021). All the Bemaraha tridactyl footprints belong to theropods with a hip height estimated by standard methods (Thulborn 1990) to be about 1.50 + 0.25 m. ...
Article
The Bemaraha Formation preserves a unique and abundant record of dinosaur footprints, the only occurrence of this type known from Madagascar. Theropod and sauropod tracks occur in Middle Jurassic strata and form an important record from this otherwise poorly documented time interval. Here we report on 18 new tracksites, raising the total number of known localities in the Bemaraha to 31. The majority of these sites occur at a same stratigraphic level that can be traced over an area of at least 30 km ² , which makes it one of the most laterally extensive occurrences of dinosaur tracks on record in the southern hemisphere. Dinosaur tracks are restricted to a few bedding surfaces representing times of sea-level lowstand within a normally marine environment. Theropod tracks are by far more abundant than sauropod tracks and typically are oriented towards the palaeocoastline. This pattern is interpreted as evidence of a short-scale migration between feeding and resting grounds. The Bemaraha Formation thus allows a rare glimpse into dinosaur behaviour in a marginal marine environment of Jurassic age.
... Yet despite the great potential of these data and numerous recent advances in hominin ichnology, there still exist major obstacles that limit access to the invaluable information preserved by fossil hominin tracks. Perhaps the most important obstacle is our currently limited understanding of the complex interactions between foot anatomy, kinematics and substrate through which a track is formed [18][19][20]. Morse et al. [21] demonstrated, through a case study of Holocene human tracks from Namibia, that track morphology can vary substantially as the same individual walks through substrates of different consistencies. Yet the underlying reasons for that variation remain unknown. ...
Article
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The emergence of bipedalism had profound effects on human evolutionary history, but the evolution of locomotor patterns within the hominin clade remains poorly understood. Fossil tracks record in vivo behaviours of extinct hominins, and they offer great potential to reveal locomotor patterns at various times and places across the human fossil record. However, there is no consensus on how to interpret anatomical or biomechanical patterns from tracks due to limited knowledge of the complex foot-substrate interactions through which they are produced. Here, we implement engineering-based methods to understand human track formation with the ultimate goal of unlocking invaluable information on hominin locomotion from fossil tracks. We first developed biplanar X-ray and three-dimensional animation techniques that permit visualization of subsurface foot motion as tracks are produced, and that allow for direct comparisons of foot kinematics to final track morphology. We then applied the discrete element method to accurately simulate the process of human track formation, allowing for direct study of human track ontogeny. This window lets us observe how specific anatomical and/or kinematic variables shape human track morphology , and it offers a new avenue for robust hypothesis testing in order to infer patterns of foot anatomy and motion from fossil hominin tracks.
... Fossil trackways provide invaluable information about extinct faunal assemblages, and the palaeodistribution, foot morphology, locomotion and behaviour of extinct animals (Alexander, 1976;Falkingham, 2014;Sarjeant, 1995). Middle Jurassic trackways are relatively well known from the British Isles, for example there are extensive sites in Yorkshire (Romano & Whyte, 2003a), Oxfordshire (Day et al., 2004), and the Isle of Skye (e.g., dePolo et al., 2018Romano et al., 2018). ...
Article
We describe a new and unusual vertebrate trackway from the Middle Jurassic Scalby Formation of the Cleveland Basin, Yorkshire, United Kingdom. The Enigmatic Burniston Trackway (EBT) is the first and only example of such a trackway known from this region. The best preserved EBT print, belonging to a pentadactyl tetrapod, does not resemble any known Middle Jurassic ichnogenus, but shares features with Triassic and Cretaceous archosaur and synapsid ichnotaxa. EBT most closely resembles the Triassic ichnogenus Synaptichnium in having the longest digit III, shortest digits I and V, and digit V positioned posterior to the other digits. Synaptichnium has been assigned to various trackmakers, including crocodylomorphs, and early archosaurs (‘thecodonts’ and aetosaurs). However, the anteriorly oriented digits and reduced and posterolaterally placed digit V of EBT also resemble Sederipes from the Cretaceous, and Dicynodontipus from the Permian-Triassic (both representing large-bodied synapsid or ‘mammal’ trackmakers). Unlike most traces assigned to cynodont (including mammalian) or crocodylomorph makers, EBT has low total digit divergence. Digit imprints end in short claws and the pes is rotated by ∼20° outwards in relation to the manus. Preservation is fragmentary for most of the trackway and the specimen could not be collected, but we record it here and provide comparative context within the existing ichnofossil record. We discuss the issues regarding ‘mammal’ ichnofossil literature, including taxonomic nomenclature, inconsistent diagnostic criteria, and assumptions made previously about Mesozoic synapsid body mass.
... As it, they represent an original snapshot on the composition of groups and their behaviours during their lives (e.g. Mastrolorenzo et al. 2006;Hasiotis et al. 2007;Schmincke et al. 2010;Falkingham 2014). They differ in this respect from skeletal or lithic material whose accumulations may have occurred during various and repeated occupations over long periods (Farizy 1994;Pettitt 1997). ...
... As it, they represent an original snapshot on the composition of groups and their behaviours during their lives (e.g. Mastrolorenzo et al. 2006;Hasiotis et al. 2007;Schmincke et al. 2010;Falkingham 2014). They differ in this respect from skeletal or lithic material whose accumulations may have occurred during various and repeated occupations over long periods (Farizy 1994;Pettitt 1997). ...
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Hominin tracks represent a unique window into moments in the life of extinct individuals. They can provide biological and locomotor data that are not accessible from skeletal remains. However, these tracks are relatively scarce in the fossil record, particularly those attributed to Neandertals. They are also most often devoid of associated archaeological material, which limits their interpretation. The Palaeolithic site of Le Rozel (Normandy, France) located in a dune complex formed during the Upper Pleistocene has yielded between 2012 and 2017 several hundred tracks (257 hominin footprints, 8 handprints as well as 6 animal tracks). This ichnological assemblage is distributed within five stratigraphic subunits dated to 80,000 years. These subunits are rich in archaeological material that attests to brief occupations by Neandertal groups and provides information about the activities that they carried out. The ichnological assemblage discovered at Le Rozel is the largest attributed to Neandertals to date and more generally the most important for hominin taxa other than Homo sapiens. The particularly large number of footprints can provide major information for our understanding of the Palaeolithic occupations at Le Rozel and for our knowledge of the composition of Neandertal groups.
... In fact, this stratigraphic section was used to 524 establish the site formation model for the sloth-human trackway (see Figure 5A) intersections. For instance, the longer this surface was exposed, the greater the chance that trackway 600 forming events occurred sporadically over much broader time scales, such as days, weeks, years, or 601 possibly millennia (Falkingham, 2014). This would increase the likelihood of superimposed tracks and 602 trackways that formed during different unrelated track forming events (Lockley and Hunt, 1995). ...
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The margins of Paleolake Otero in southern New Mexico, USA, contain one of the largest concentrations of fossilized late Pleistocene (Rancholabrean) megafauna trackways in North America. These fossil footprints include tracks of Ice Age proboscideans, ground sloth, dire wolf, and camelids, as well as humans. Biomechanical interpretations of these fossil footprints suggest that prehistoric people in the basin regularly interacted with the megafauna. However, these trackway studies employ a geomorphic context that assumes an unlikely static landscape that changed very little after the human–megafauna interaction occurred during much of the terminal Pleistocene to the latest Holocene. In this study, we present a new lacustrine paleoclimate record from the western margin of Paleolake Otero to demonstrate that the lake underwent six developmental phases as lake levels waxed and waned at the end of the last Ice Age, reflecting a dynamic shoreline. We also reconcile how different factors have complicated the currently proposed timing of these human–megafauna trackway intersections; namely, the lake is now thought to have persisted during the terminal Pleistocene longer than previously thought, and multiple older pre-Ice Age trackways are thought to have been exhumed by Holocene wind erosion. Finally, we propose an alternative model that states that the human trackways are not contemporaneous with nearby megafauna trackways, but simply reflect humans crossing over re-exhumed, and much older, trackway surfaces.
... The morphology of the vertebrate tracks is determined by both the trackmaker, including foot anatomy and locomotor dynamics, and the substrate properties such as grain size, composition, moist content and consistency (Manning, 2004;Milàn, 2006;Díaz-Martínez et al., 2009;Marty et al., 2009;Falkingham, 2014). Track morphology also depends on the relation between the stratigraphic level in which are observed the tracks (e.g. ...
Article
Several dinosaur tridactyl tracks showing inter- and intra-trackways morphological variations from the Cenomanian Candeleros Formation of the Neuquén Basin, Argentina, have been documented. Footprints occur on three different stratigraphic levels and are impressed on medium-grained sandstone of fluvial origin. Level 1 includes deep tridactyl tracks with metatarsal impressions (average length of 31 cm) preserved as true tracks and undertracks that could have been generated due to simply sinking of the pes into a soft substrate and also probably by a continuous walk in a squatting position. Level 2 shows the largest tridactyl tracks (average length of 58 cm) recognized in this work, situated a few meters close to an already studied sauropod trackway. The different preservation between these bipedal and quadrupedal tracks could be explained due to different substrate properties and dissimilarities of the pedal shape between trackmakers. Level 3 comprises small to large tridactyl tracks (length from 6 to 34 cm) including intra-trackway morphological variation, that is interpreted as a result of changes in the substrate properties, mainly moisture content, along the tracking surface. Taking into account that the footprints studied here are poorly preserved, they were not assigned to any particular ichnotaxon. The large tridactyl tracks have been attributed to carcharodontosaurid theropod trackmakers while medium and small tracks to undetermined bipedal dinosaur. One pair of these large theropod tracks was closely documented on the same tracking surface of the aforementioned studied sauropod trackway, attributed to rebbachisaurids. This suggests that both carcharodontosaurid and rebbachisaurid trackmakers coexisted in the same habitats as the osteological record noted. This tracksite represents an example of the morphological variability of dinosaur tridactyl tracks controlled mainly by the substrate properties, and how an approach aimed at understanding footprint formation and preservation is necessary before beginning ichnotaxonomical studies, among others.
... Vertebrate tracks are three-dimensional (3D) products resulting from the interaction between a trackmaker and the substrate over which the animal moves (Falkingham 2014). These products can be preserved as either true tracks, natural casts or undertracks (also known as transmitted prints or ghost prints; Lockley 1991). ...
Article
The upper Stormberg Group of Lesotho has an abundant and diverse ichnological record that dates to the Early Jurassic. Herein, we re-evaluate a known ichnosite in the lowermost Clarens Formation (Karoo Supergroup) at Tsikoane in northern Lesotho. The site was reported to preserve tridactyl tracks as natural casts in the ceiling of overhangs and true track impressions on a fallen sandstone block. At least three track-bearing palaeosurfaces, associated with horizontally laminated sandstones and desiccated green mudstones, can be traced over a distance of 250 m. Associated with one of the track-bearing palaeosurfaces, discrete, U-shaped, cross-sectional structures are interpreted as a series of natural casts, surface tracks, true tracks and undertracks. Although the Tsikoane tracks were historically assigned to a single ichnogenus, later synonymised with Grallator, our findings show a higher diversity of tridactyl ichnites, with tracks that have Kayentapus-like and Eubrontes-like features in addition to previously recognised Grallator-like features. These new findings, within their high-resolution sedimentological context, improve the understanding of theropod palaeodiversity and palaeoecology in southern Africa during a crucial period in dinosaur history marked by increases in both abundance and diversity.
... A commonly shared, practical approach to the understanding of the dynamics of the registration process relates the final morphology of a trace to three main factors: organism morphology, organism behaviour and substrate properties (e.g. Padian and Olsen, 1984;Minter et al., 2007;Falkingham, 2014). The traces left on the Moon are unique for several reasons, namely, humans have been the only organisms trampling and interfering with the Moon's soil during exploration campaigns. ...
Article
Humankind began with extra-planetary expeditions in the 1960s. To date, more than fifty manned and unmanned lunar missions have taken place. Maybe, the most iconic image of these campaigns is the bootprint left and photographed by the astronaut Edwin Aldrin. Nevertheless, there is also other evidence of human activities on the Moon, such as rover trails, drill holes, vehicles, and rubbish. For some researchers, ichnology only studies the traces made by one or several individuals with their own bodies, but other authors advocate that artefacts as well as traces made by these artefacts are also traces. In this context, the ichnology of the Moon allows both analysis of the traces left on the lunar surface themselves and discussion of the aim and scopes of ichnology. The Moon ichnology, which arises from the development of hominid ichnology, includes technical artefacts (called technofossils, e.g. Lunar Module, flag, religious text) and traces of technical artefacts (comprised in the new category technotraces, e.g. bootprints, drill holes) but not traces made by individuals with parts of their bodies. Although the lunar environment is very different from that of the Earth due to the absence of atmosphere, magnetic field, water, organic material and life, it is possible to propose three ichnological analogies between the Earth and its satellite. First of all, traces on the Moon surface are subjected to very slow sedimentation rates, similar to what occurs in abyssal bottoms or caves, among other environments. Moreover, physical and mechanical properties allow comparison with processes leading to the formation of traces in volcanic ash deposits with those acting on the soil and regolith of the Moon. Finally, cultural similarities have been identified between the traces left by humans on the Moon and comparable expeditions of humankind, such as Antarctica and the North Pole. The evolution of human technical artefacts has been used to help characterise the onset of the “Anthropocene”. These artefacts can be included within the technosphere and can also be thought to be phenotypic expressions of human genes. Therefore, the traces left on the Moon as well as others which are in other celestial bodies or even in the space, can be considered evidence of extended phenotype of Homo sapiens and the “Anthropocene” beyond the Earth.
... L'un des principaux intérêts des empreintes est qu'elles ouvrent une fenêtre vers des moments de vie d'individus appartenant à des populations passées (e.g. Mastrolorenzo et al., 2006 ;Hasiostis et al., 2007 ;Falkingham, 2014). Leur étude permet d'estimer de nombreuses caractéristiques biologiques informant sur la composition de groupes pendant de brèves périodes (e.g. . ...
Thesis
Les empreintes de pieds d’hominines représentent des vestiges uniques ouvrant une fenêtre sur de brefs moments de vie de groupes disparus. Leur étude donne des informations directes sur la taille et la composition de ces groupes, paramètres essentiels à leur succès adaptatif mais rarement accessibles à partir du registre fossile. Toutefois, l’étude des empreintes est rendue complexe par le nombre de facteurs (caractéristiques corporelles et biomécaniques, nature du substrat, taphonomie) impactant leur morphologie et leur relative rareté au sein du registre fossile. Depuis 2012, plusieurs centaines d’empreintes de pieds potentielles attribuables à des néandertaliens ont été découvertes associées à un riche matériel archéologique dans 5 niveaux datés à 80 000 ans de la paléodune du Rozel (Manche, France). La découverte de ces empreintes offre l’opportunité de s’intéresser à la taille et à la composition des groupes sociaux néandertaliens, problématique centrale de ce doctorat. Dans un premier temps, l’analyse des empreintes potentielles découvertes entre 2012 et 2017 a permis d’identifier 257 empreintes de pieds et 8 empreintes de mains ce qui représente à ce jour le plus gros corpus ichnologique associé aux Néandertaliens. Puis, grâce au développement d’une approche combinant morphométrie et expérimentation, la taille et la composition des groupes a été estimée à partir des empreintes numérisées en 3D. Les empreintes de pieds étudiées reflètent ainsi différentes classes d’âge allant du très jeune enfant (à partir de 1 an) à l’adulte. Les empreintes issues du niveau le plus dense ichnologiquement représentent un groupe de petite taille, probablement composé de 10 à 13 individus, dont 90% étaient des enfants et des adolescents. Les empreintes de pieds du Rozel fournissent ainsi des informations uniques sur la taille et la composition des groupes néandertaliens permettant de mieux comprendre les occupations paléolithiques au Rozel il y a 80 000 ans.
... That is because of the highly sloped track walls at the anterior of the track, most likely resulting from an anterior or posterior motion of the foot and ground reaction force during locomotion. It is worth noting therefore that the three factors determining track morphology (foot anatomy, kinematics, and substrate) may affect different parameters of the track to differing extents, even within a single footfall (Falkingham, 2014). There is also a shortening of length because the track floor is not parallel to the tracking surface -it is deeper under the distal digits than under the metatarsal pad, due to increased pressure at toe-off. ...
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The collection and dissemination of vertebrate ichnological data is struggling to keep up with techniques that are becoming commonplace in the wider palaeontological field. A standard protocol is required to ensure that data is recorded, presented and archived in a manner that will be useful both to contemporary researchers, and to future generations. Primarily, our aim is to make the 3D capture of ichnological data standard practice, and to provide guidance on how such 3D data can be communicated effectively (both via the literature and other means) and archived openly and in perpetuity. We recommend capture of 3D data, and the presentation of said data in the form of photographs, false‐colour images, and interpretive drawings. Raw data (3D models of traces) should always be provided in a form usable by other researchers (i.e. in an open format). If adopted by the field as a whole, the result will be a more robust and uniform literature, supplemented by unparalleled availability of datasets for future workers.
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Background. Minute to medium-sized (FL less than 30 cm) tridactyl dinosaur tracks are the most abundant in the Late Jurassic tracksites of Highway A16 (Reuchenette Formation, Kimmeridgian) in the Jura Mountains (NW Switzerland). During excavations, two morphotypes, one gracile and one robust, were identified in the field. Furthermore, two large-sized theropod ichnospecies ( Megalosauripus transjuranicus and Jurabrontes curtedulensis ) and an ornithopod-like morphotype (Morphotype II) have recently been described at these sites. Methods. The quality of preservation (preservation grade), the depth of the footprint, the shape variation and the footprint proportions (FL/FW ratio and mesaxony) along the trackways have been analysed using 3D models and false-colour depth maps in order to determine the exact number of morphotypes present in the tracksites. Results. The study of the footprints (n = 93) collected during the excavations has made it possible to identify and characterize the two morphotypes distinguished in the field. The gracile morphotype is mainly characterized by a high footprint length/width ratio, high mesaxony, low divarication angles and clear, sharp claw marks and phalangeal pads (2-3-4). By contrast, the robust morphotype is characterized by a lower footprint length/width ratio, weaker mesaxony, slightly higher divarication angles and clear, sharp claw marks (when preserved), whereas the phalangeal pads are not clearly preserved although they might be present. Discussion. The analysis does not allow the two morphotypes to be associated within a morphological continuum. Thus, they cannot be a consequence of extramorphological variations on similar tracks produced by a similar/single trackmaker. Comparison of the two morphotypes with the larger morphotypes described in the formation ( Megalosauripus transjuranicus , Jurabrontes curtedulensis and Morphotype II) and the spatio-temporal relationships of the trackways suggest that the smaller morphotypes cannot reliably be considered small individuals of the larger morphotypes. The morphometric data of some specimens of the robust morphotype (even lower values for the length/width ratio and mesaxony) suggest that more than one ichnotaxon might be represented within the robust morphotype. The features of the gracile morphotype (cf. Kalohipus ) are typical of “grallatorid” ichnotaxa with low mesaxony whereas those of the robust morphotype (cf. Therangospodus and ? Therangospodus ) are reminiscent of Therangospodus pandemicus . This work sheds new light on combining an analysis of variations in footprint morphology through 3D models and false-colour depth maps, with the study of possible ontogenetic variations and the identification of small-sized tridactyl ichnotaxa for the description of new dinosaur tracks.
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The Vértesszőlős quarry, the Palaeolithic site where the “Samu” hominin fossil remains (Homo heidelbergensis) were found, is located in North West Hungary. The site is dated between the Early and Middle Pleistocene (ca. 310 ka). A short distance from where the Samu remains were found is an exposed surface of calcareous mudstone, preserving numerous fossil tracks made by a range of mammals and birds. Of particular interest are three elongate impressions - two potentially successive and one isolated. These tracks have previously been referred to either hominin or ursine trackmakers. Since bear pes tracks can superficially resemble human tracks, we attempted to discern the 3D morphology of the traces using digital photogrammetry. Our analysis suggests the isolated impression is likely the product of two superimposed tracks of a cloven hoofed ungulate. However, the two potentially successive tracks are more problematic. The highly weathered surface (first exposed in the 1960’s) has made interpretation difficult. Both impressions seem to possess a narrow, rounded end similar to the posterior heel margin of a human track. At the anterior end the impressions are broader, and bounded by smaller impressions that could be interpreted as toe marks. However, these two tracks differ considerably in their length/width ratios and are too widely spaced to be part of a single bipedal trackway. It is conceivable that one or both of these impressions may be highly weathered hominin tracks. However, given the highly weathered nature of the exposed surface, and the lack of morphological detail in the tracks, we cannot at this time confidently attribute the tracks to any specific trackmaker, despite our digital models of the tracks provide a means of analysis being relatively objective, and independent from prior assumptions.
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Background. Minute to medium-sized (FL less than 30 cm) tridactyl dinosaur tracks are the most abundant in the Late Jurassic tracksites of Highway A16 (Reuchenette Formation, Kimmeridgian) in the Jura Mountains (NW Switzerland). During excavations, two morphotypes, one gracile and one robust, were identified in the field. Furthermore, two large-sized theropod ichnospecies ( Megalosauripus transjuranicus and Jurabrontes curtedulensis ) and an ornithopod-like morphotype (Morphotype II) have recently been described at these sites. Methods. The quality of preservation (preservation grade), the depth of the footprint, the shape variation and the footprint proportions (FL/FW ratio and mesaxony) along the trackways have been analysed using 3D models and false-colour depth maps in order to determine the exact number of morphotypes present in the tracksites. Results. The study of the footprints (n = 93) collected during the excavations has made it possible to identify and characterize the two morphotypes distinguished in the field. The gracile morphotype is mainly characterized by a high footprint length/width ratio, high mesaxony, low divarication angles and clear, sharp claw marks and phalangeal pads (2-3-4). By contrast, the robust morphotype is characterized by a lower footprint length/width ratio, weaker mesaxony, slightly higher divarication angles and clear, sharp claw marks (when preserved), whereas the phalangeal pads are not clearly preserved although they might be present. Discussion. The analysis does not allow the two morphotypes to be associated within a morphological continuum. Thus, they cannot be a consequence of extramorphological variations on similar tracks produced by a similar/single trackmaker. Comparison of the two morphotypes with the larger morphotypes described in the formation ( Megalosauripus transjuranicus , Jurabrontes curtedulensis and Morphotype II) and the spatio-temporal relationships of the trackways suggest that the smaller morphotypes cannot reliably be considered small individuals of the larger morphotypes. The morphometric data of some specimens of the robust morphotype (even lower values for the length/width ratio and mesaxony) suggest that more than one ichnotaxon might be represented within the robust morphotype. The features of the gracile morphotype (cf. Kalohipus ) are typical of “grallatorid” ichnotaxa with low mesaxony whereas those of the robust morphotype (cf. Therangospodus and ? Therangospodus ) are reminiscent of Therangospodus pandemicus . This work sheds new light on combining an analysis of variations in footprint morphology through 3D models and false-colour depth maps, with the study of possible ontogenetic variations and the identification of small-sized tridactyl ichnotaxa for the description of new dinosaur tracks.
Article
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Whilst bones present a static view of extinct animals , fossil footprints are a direct record of the activity and motion of the track maker. Deep footprints are a particularly good record of foot motion. Such footprints rarely look like the feet that made them; the sediment being heavily disturbed by the foot motion. Because of this, such tracks are often overlooked or dismissed in preference for more foot-like impressions. However, the deeper the foot penetrates the substrate, the more motion is captured in the sediment volume. We have used deep, penetrative, Jurassic dinosaur tracks which have been naturally split into layers, to reconstruct foot motions of animals living over 200 million years ago. We consider these reconstructions to be hypotheses of motion. To test these hypotheses, we use the Discrete Element Method, in which individual particles of substrate are simulated in response to a penetrating foot model. Simulations that produce virtual tracks morphologically similar to the fossils lend support to the motion being plausible, while simulations that result in very different final tracks serve to reject the hypothesis of motion and help generate a new hypothesis.
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Yunnan Province is famous for its diversified Lufeng vertebrate faunas containing many saurischian dinosaur remains. In addition to the body fossil record, dinosaur ichnofossils have also been discovered in Yunnan, and the number of published track sites is on the rise. We report a theropod assemblage from the Lower Jurassic Fengjiahe Formation in Xiyang, central Yunnan. It is the third report and description of dinosaur footprints from the Fengjiahe Formation, and this new track site is the largest in number of footprints for theropods in Yunnan. Over one hundred footprints are preserved on different layers of a claystone-dominated succession close to the Lower-Middle Jurassic boundary. The track area is referred to as a lacustrine shallow-water paleoenvironment. Tracks vary in size, morphology, and preservation. All are tridactyl and digitigrade, and some are identified as undertracks. The best preserved footprints were divided into three morphotypes: morphotype A (>8 cm–27 cm–
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In a neoichnological study, the trackway of a small recent bird (Limicola- like) crossing the slope of a river bank is documented and analyzed in detail. It was preserved along the Issene River in the western High Atlas of Morocco. Photogrammetry and 3-D techniques revealed three different phases of the trackmaker's movement that were essentially controlled by the biomechanical adaptations of the limbs and by the differences in how the foot was indented from up to down slope on the tilted, mud-cracked surface of the tilted mud-cracked surface. The slope of the surface is reflected in the variation of different track parameters, such as stride length, pace length, pace angulation, and imprint depths of different digits. A “didactyl” or fully collapsed morphology preservation pattern is observed as an intra-trackway morphological variation along the whole trackway. Tracks preserve only the up-slope digits: left tracks typically preserve only digit III and IV impressions, while right tracks preserve only digit III and II impressions. The selective absence of impressions of the other digits is interpreted to be the combined product of a water saturated/damp consistency of the sediment at the time of track formation and of the “down-facing” position of the unimpressed digits the latter reflects the differences in the bearing capacities of the “up-slope” portion of the limb versus the “down-slope” portion. The study may be helpful for understanding fossil counterparts formed on similarly uneven terrain.
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The functional anatomy of the hindlimb of bipedal dinosaurs has been intensively studied. Yet, surprisingly little work has been done concerning functional adaptation of digits for terrestrial locomotion. While complete and articulated pes skeletons are scarce, pes shape is abundantly recorded by fossil footprints. We elucidate the significance of footprint shape and size for locomotion using a large sample (n = 303) of tridactyl dinosaur footprints from a broad range of geographical localities and time slots. Size and shape variation are characterized separately for theropods and ornithischians, the two principal trackmaker taxa. At smaller sizes, theropod footprints are best discriminated from ornithischian footprints by their smaller interdigital angle and larger projection of digit III; at larger sizes digital widths are effective discriminants. Ornithischian footprints increase in size from the Early Jurassic to the Late Cretaceous, a trend not observed in theropod footprints. Size and function are argued to be important determinants of footprint shape, and an attempt made to infer function from shape. Digit III projection and length‐to‐width ratio of the footprints are negatively correlated with size in both groups; digit impression width is positively correlated with size only in ornithischians. Digit III projection appears to be positively correlated with cursorial ability. Increased interdigital angles are associated with a decrease in digital width, possibly an adaptation for stability. Weak digit III projection and increased digital width are interpreted as adaptations for graviportality. Footprints yield great potential for the understanding of the functional morphology of dinosaur feet.
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The feet of ground-dwelling birds retain many features of their dinosaurian ancestry. Experiments with living species offer insights into the complex interplay among anatomy, kinematics and substrate during the formation of Mesozoic footprints. However, a key aspect of the track-making process, sub-surface foot movement, is hindered by substrate opacity. Here, we use biplanar X-rays to image guineafowl walking through radiolucent substrates of different consistency (solid, dry granular, firm to semi-liquid muds). Despite substantial kinematic variation, the foot consistently moves in a looping pattern below ground. As the foot sinks and then withdraws, the claws of the three main toes create entry and exit paths in different locations. Sampling these paths at incremental horizons captures two-dimensional features just as fossil tracks do, allowing depth-based zones to be characterized by the presence and relative position of digit impressions. Examination of deep, penetrative tracks from the Early Jurassic confirms that bipeds had an equivalent looping response to soft substrates approximately 200 Ma. Our integration of extant and extinct evidence demonstrates the influence of substrate properties on sinking depth and sub-surface foot motion, both of which are significant sources of track variation in the fossil record of dinosaurs.
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Abstract Prehistoric Man, who depended on hunting for food, certainly would have had a varied terminology for animai tracks, as indeed do the surviving primitive tribes. Contemporary hunters can defme a track based upon many parameters, while using technical terms. Good hunters, especially the primitive ones, are able to determine the species, sex, age, conditions of health, gait and other information about the animai, based on empirical observations of trackways and the trackmakers. Technical terminology for tracks has been used in scientific publications since the first half of the nineteenth century. However, the systematization of these therms took place much later, in generai only whithin the last few decades. Probably the first published listing of terms is the very short one, published (in English) by Frank E. Peabody in 1948 and revised in 1959. The first glossary in French was published by Heyler and Lessertisseur (1963) and is more extensive than the preceding one. It includes some information on measurement techniques. Also in French is the glossary and rnanual found in the introduction to an important monograph by G. R. Demathieu (1970). In German there are good listings of terms in the introduction of two works by Haubold (1971), as well as in his book "Saurierfährten" (1984). Casamiquela (1964) formalized an ichnological terminology in Spanish; in the same work he established methods of study and interpretation of tracks. Sarjeant's review of the tetrapod footprints (1975) is remarkable; it contains important considerations on the measurement, analysis, interpretation and terminology of footprints. M.T. Antunes (1976) presented a study on tracks of dinosaurs from Lagosteiros (Portugal); and first used technical terms in Portuguese. The first attempt at a comparative glossary in seven languages was compiled by G. Leonardi (1979). The glossary put side by side the majority of terms used in English, French, German, Spanish, Italian, Portuguese and Latin; and a list of terms was presented for the first time in a systematic way in the three last languages. Initial contacts for the present work were made in 1977 at the iniciative of this editor. Work started in 1979 and has taken eigth years. It encompasses more than 2500 terms (2588 altogheter; 1271 ichnological; 218 anatomical; 417 biomechanical; 149 on the substratum; 533 statistical. 361 in Spanish; 373 in German; 305 in English; 317 in French; 312 in Italian; 296 in Latin; 326 in Portuguese; 298 in Russian). It was by no means an easy task to unify methods of study and measurement. The patience of my good friends and colleagues in filling out forms, lists and ques-tionnaires was infinite. The contribution of each is specified under the title of each chapter and also, in an abridged form, in the columns of terms for each language. Bill Sarjeant carefully revised the text in English. English was the language chosen for the text because, unfortunately, there is no neutral language. English can be understood by all the ichnologists. Clearly, it would be impossible to publish the text in many languages. The glossary deals with the ichnology of the tetrapods; with trackways and footprints, but not with other vertebrate traces such as eggs, coprolites and dens. The work is presented in following order. First a lengthy introduction to the history of the ichnology of vertebrates (with a selective bibliography) by Bill Sarjeant: Secondly the glossary of terms is presented in eight languages, i.e. the seven languages accepted by the International Code of Zoological Nomenclature and also Portuguese, because it is the language of this editor and of the country (Brazil) where the Work will be published. In Brazil, ichnology has lately received considerable support from the cultural and political milieux (The Ministry of Mines and Energy, inter alia), and from the institutions providing financial help for research, especially the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and the Departamento Nacional da Produção Mineral (DNPM). The subject has aroused great interest also among the Brazilian press and the general public, due to its great fascination. The columns of terms, from left to right, are in alphabetical order of the names of the different languages: from "Castellano" to "Russian". (For "Spanish" we preferred the more correct name of "Castellano", in English, "Castilian" — as distinct from "Catalan"). In each column, the terms are not entered in alphabetical order; instead they are divided into areas (Ichnology, Anatomy, Biornechanics, Substratum, Statistics) since this was felt to be more potentially helpful. In the first section there is a logical order, with general terms first, then with the terms concerned with the trackway, the footprint, and the morphological details of the footprint. The order in each section is not arbitrary, as it may seem at first. It aims to introduce first the basic terms, which are necessary to the understanding and usage of the terms that follow. The position of one or another term is sometimes debatable and might have been done differently. The alphabetical index simplifies location of terms in the glossary and in the discussion. The choice of terms for the substrate (in English) was the work of Bill Sarjeant. The terms for Statistics were chosen by Georges R. Demathieu; consequently they appear in the French alphabetical order. The Statistics section is probably too large: some of the authors found it disproportionate compared to the other sections. Nevertheless I decided to publish it anyway. The difficulty we had in finding equivalent terms in the different linguistic columns convinced us that a statistica glossary in eight languages probably does not exist. Consequently, this section may make easier the reading and linguistic correlation of terms not only for ichnologists but also for paleontologists at large, and maybe even for other researchers. It is an "extra" that we offer to the scientific community! Furthermore, statistics is a science that has only recently been applied to ichnology: some terms, methods and concepts that are not employed in our field yet may be utilized in the near future. Besides the terms already widely used, we introduced some new terms formed by analogy with other languages or by simply transforming adjectives into nouns (as in the example: mesaxonic — mesaxony — axony). Ichnology is a living science, growing rapidly today, so it is understandable that neologisms develop. It was not possible to include all the terms in every column, in part because sometimes we could not find equivalents, but more often because the author responsible for the column did not think it opportune to include in his own language a term that migth be perfect in the other languages, but did not sound right to him. In Latin (that of the scientific milieu and of the western catholic Church) we could not find neologisms that could express some concepts. We have also created some new terms — not in excess, however! The terms cannot always be simply translated, since there are significant conceptual and logical differences between the different languages. Note, for instance, the term "pace" in English. The author responsible for the English language in our glossary thinks that it already includes the concept of "oblique" which in other languages, has to be made explicit. Those terms which are commonly used in the existing literature but which should be avoided because they are either improper or confusing, are placed in parentheses. Optional complements are placed within brackets. In the third section, there is a lengthy discussion of the mean-ing of the terms, by Giuseppe Leonardi. Besides explaining the terms and discussing the relationship between the languages whenever necessary, there is also a discussion concerning the correct way of making the measurements. Included also are some considerations and suggestions on the study of footprints in generai. We had to face up to many semantic difficulties in our attempt to unify the methods of the different countries and schools during the preparation of this text. The numbering of items in the chapter "Discussion etc." is obviously the same as the lists of terms. Each number or item refers to a term or a group of terms. Some special topics follow in an appendix — apparent limbs; thickness of footprint-relief and its significance; research on the distribution of the weight upon the autopodia; and a table of the phalangeal formulae of the reptiles. To conclude, I would like to sumarize briefly our objectives we pursuecl in publishing this work. As already mentioned, ichnology is expanding and an increasing number of papers on this subject are being written in different languages. Correlating terms is not always an easy task; and descriptive methods are often different from school to school, and from country to country. This work is an attempt to unify methods and to correlate terrninologies in eight languages. The utilization of our glossary in future study on vertebrate ichnology shall make possible, to ichnologists in different parts of the world, the understanding of the methods of measurement and study used in any particular paper and of the exact meaning of the terms employed. The future translation and publishing of our lists of terms in other languages by other authors may further widen the common international platform for our field. We hope we have rendered useful service to the ichnological community. Maybe because we are only a few around the world, we constitute a friendly community where everyone knows each other. Our hope is that some day we may all come to use the same methods and in this way, come to understand each other better. Brasilia, October 12, 1986. Giuseppe Leonardi Editor
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A fundamental question remaining unanswered in dinosaur behavior is whether they had the ability to swim. We report the discovery of an exceptional swimming dinosaur trackway, with 12 consecutive footprints, in lacustrine nearshore sediment from the Early Cretaceous Cameros Basin, La Rioja, Spain. The singular morphology of these footprints strongly suggests a floating animal clawing the sediment as it swam. Diagnostic traits of theropod dinosaur footprints are identifiable in these peculiar elongated S-shaped ichnites. Paleoenvironmental reconstruction indicates an upper shoreface setting with a maximum water depth of ˜3 m, substantiating the swimming hypothesis. Ichnological analysis of the trackway shows that this theropod used a pelvic paddle motion, similar to that of modern bipeds, and swam with amplified asymmetrical walking movements to maintain direction into a leftward water current. After recent hints of swimming dinosaurs, this new evidence persuasively demonstrates that some non-avian theropod dinosaurs were swimmers.
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Dinosaur footprints have been used extensively as biostratigraphic markers, environmental indicators, measures of faunal diversity and evidence of group behaviour,. Trackways have also been used to estimate locomotor posture, gait and speed, but most prints, being shallow impressions of a foot's plantar surface, provide little evidence of the details of limb excursion. Here we describe Late Triassic trackways from East Greenland, made by theropods walking on substrates of different consistency and sinking to variable depths, that preserve three-dimensional records of foot movement. Triassic theropod prints share many features with those of ground-dwelling birds, but also demonstrate significant functional differences in position of the hallux (digit I), foot posture and hindlimb excursion.
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The trackway of a swimming theropod (ichnogenus Characichnos) is reported from the Lower Cretaceous Feitianshan Formation of Sichuan, China. These swim tracks help confirm that non-avian theropods were capable of forging moderately deep bodies of water. The trackway occurs on the same surface as a typical walking trackway of a sauropod (ichnogenus Brontopodus). Both occurrences are the first reported from the Cretaceous of Sichuan, and the swim tracks are the first well-preserved example of a Characichnos trackway from China. Additionally, a theropod walking trackway and several ornithopod walking trackways (similar to the ichnogenus Caririchnium) occur in the same horizon. The ornithopod trackways show a parallel orientation, suggesting gregarious behavior of the trackmakers, which may have been iguanodontiforms and/or hadrosauriforms. The co-occurrence of theropod swim tracks and theropod walking tracks suggests a fluctuation of water depth within a distinct time span.
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Abstract: Increasing political and social awareness of the importance of protecting the geological heritage is compelling geoscientists to consider new methods for reconciling conservation and exploration of their research sites. Terrestrial Light Detection And Range (LiDAR) imaging is an accurate method of collecting 3D spatial data that has so far been under-utilized in the geological sciences. This aim of this paper is to assess the value of integrated LiDAR and photogrammetric imaging as a tool for synchronizing scientific exploration with conservation of geological heritage sites. Fumanya (Catalonia) is one of the most important Cretaceous tracksites in Europe, but the nature of exposure of the track-bearing surface has hindered quantitative documentation of the ichnites. Using integrated Light Detection And Range (LiDAR) imaging and photogrammetry it has been possible to construct highresolution Digital Outcrop Models (DOM) of the tracksites. Photo-textured DOMs are a powerful visualization tool and function as fully 3D interactive databases that preserve information about the site that would otherwise be lost to erosion. LiDAR-derived DOMs have the potential to contribute profoundly to future geoconservation projects, particularly as a tool for documenting and monitoring heritage sites and promoting education and tourism. LiDAR scanning also provides sufficient resolution to perform robust quantitative analysis of dinosaur tracks.
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An Early Jurassic tetrapod tracksite in the upper Elliot Formation at Moyeni, southern Lesotho, displays a variety of trackways attributed to large- and medium-sized theropod (Neotrisauropus-type) and ornithischian (Mol,enisauropus-type) dinosaurs, basal crurotarsal archosaurs (chirotheroid-type), and a short-legged basal tetrapod (Episcopopus-type). The tracks are on a low-angle pointbar and are buried with loessic floodplain fine-grained sediment. Calcic paleosols indicate a warm semiarid climate. Many of the footprints were imprinted through an algal mat in a water-margin setting. Convergence of several trackways toward a single point suggests repeated visits to drink or cross the river. One of the two large Moyenisauropus-type trackways has a narrow gauge that suggests an upright, parasagittal gait, whereas the other shows changes in gauge width, stance, and posture as it proceeded up the pointbar slope. At least three resting traces with manus, metatarsal, and tail impressions attributable to the Moyenisauropus-type ornithischian are also preserved. Discovery of two manus-pes pairs of chirotheroid-type footprints in the Moyeni section highlights a mismatch between the body-fossil and trace-fossil records. Chirotheroid tracks are generally thought to be restricted to the Triassic, and their discovery at the Moyeni tracksite compounds the problem of where to place the Triassic-Jurassic boundary in this succession. Three possible scenarios could explain the occurrence of chirotheroid-type tracks at Moyeni: (1) the tracksite is Late Triassic in age; (2) the chirotheroid tracks were made by archosaurs other than basal crurotarsans; (3) the tracks are correctly identified and the age of the Moyeni section is correctly assigned, but the inferred range of chirotheroid-type tracks is incorrect. We suggest that the latter two are the most likely explanations.
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Studies of dinosaur tracks have benefited from a distinction between true tracks and those made in subsurface layers—undertracks. However, the straightforward definition of true tracks becomes problematic when dealing with deep tracks, which often perforate or incise surface layers rather than simply distort them. Deep tracks from the Late Triassic of Greenland were made by theropods moving their feet through a volume of sediment along a complex three-dimensional trajectory. I suggest that designating different portions of the track as direct or indirect features is fruitful for reconstructing foot motion. Identifying which sedimentary grains, rather than which layers, were touched by the foot avoids dismissing deep tracks as undertracks and overlooking a valuable source of kinematic data.
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The fossil trackway Pteraichnus saltwashensis Stokes 1957, from the Momson For- mation of Arizona, originally attributed to a pterodactyloid pterosaur, is reassessed. We conclude that the assignment was incorrect because: 1, Pteraichnus has five toes on the manus (all pterosaurs have four); and 2, pterosaurs did not walk quadrupedally. However, trackways similar in detail to the poorly preserved Pteraichnus can be simulated experimentally by a small caiman, and we suggest that Pteraichnus could have been made by a crocodilian. Experimental work on trackways, coupled with considerations of limb kinematics and substrate conditions, will permit the most robust inferences about paleoichnologic trackmakers, and will thus maximize the utility of fossil footprint data.
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Theropod (carnivorous) dinosaurs spanned a range from chicken-sized to elephant-sized animals. The primary mode of locomotion in these dinosaurs was fairly conservative: Theropods were erect, digitigrade, striding bipeds. Even so, during theropod evolution there were changes in the hip, tail, and hindlimb that undoubtedly affected the way these dinosaurs walked and ran, a trend that reached its extreme in the evolution of birds. Some derived non-avian theropods developed hindlimb proportions that suggest a greater degree of cursoriality than in more primitive groups. Despite this, fossilized trackways provide no evidence for changes in stride lengths of early as opposed to later non-avian theropods. However, these dinosaurs did take relatively longer strides—at least compared with footprint length—than bipedal ornithischian dinosaurs or ground birds. Judging from trackway evidence, non-avian theropods usually walked, and seldom used faster gaits. The largest theropods were probably not as fleet as their smaller relatives.
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Digitization of specimens is becoming an ever more important part of palaeontology, both for archival and research purposes. The advent of mainstream hardware containing depth sensors and RGB cameras, used primarily for interacting with video games, in conjunction with an open platform used by developers, has led to an abundance of highly affordable technology with which to digitize specimens. Here, the Microsoft® Kinect™ is used to digitize specimens of varying sizes in order to demonstrate the potential applications of the technology to palaeontologists. The resulting digital models are compared with models produced using photogrammetry. Although the Kinect™ generally records morphology at a lower resolution, and thus captures less detail than photogrammetric techniques, it offers advantages in speed of data acquisition, and generation of a completed mesh in real time at the point of data collection. Whilst it is therefore limited in archival applications, the ease of use and low cost, driven by strong market competition, make this technology an enticing alternative for studies where rapid digitization of general morphology is desired.
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The gait cycle is continuous, but for practical reasons one is often forced to analyze one or only a few adjacent cycles, for example in non-treadmill laboratory investigations and in fossilized footprint analysis. The nature of variability in long-term gait cycle dynamics has been well-investigated, but short-term variability, and specifically correlation, which are highly relevant to short gait bouts, have not. We presently tested for step-to-step autocorrelation in a total of 5243 plantar pressure (PP) distributions from ten subjects who walked at 1.1m/s on an instrumented treadmill. Following spatial foot alignment, data were analyzed both from three points of interest (POI): heel, central metatarsals, and hallux, and for the foot surface as a whole, in a mass-univariate manner. POI results revealed low average step-to-step autocorrelation coefficients (r=0.327±0.094; mean±st. dev.). Formal statistical testing of the whole-foot r distributions reached significance over an average of only 0.42±0.52% of the foot's surface, even for a highly conservative uncorrected threshold of p<0.05. The common assumption, that short gait bouts consist of independent cycles, is therefore not refuted by the present PP results.
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Human footprints provide some of the most publically emotive and tangible evidence of our ancestors. To the scientific community they provide evidence of stature, presence, behaviour and in the case of early hominins potential evidence with respect to the evolution of gait. While rare in the geological record the number of footprint sites has increased in recent years along with the analytical tools available for their study. Many of these sites are at risk from rapid erosion, including the Ileret footprints in northern Kenya which are second only in age to those at Laetoli (Tanzania). Unlithified, soft-sediment footprint sites such these pose a significant geoconservation challenge. In the first part of this paper conservation and preservation options are explored leading to the conclusion that to 'record and digitally rescue' provides the only viable approach. Key to such strategies is the increasing availability of three-dimensional data capture either via optical laser scanning and/or digital photogrammetry. Within the discipline there is a developing schism between those that favour one approach over the other and a requirement from geoconservationists and the scientific community for some form of objective appraisal of these alternatives is necessary. Consequently in the second part of this paper we evaluate these alternative approaches and the role they can play in a 'record and digitally rescue' conservation strategy. Using modern footprint data, digital models created via optical laser scanning are compared to those generated by state-of-the-art photogrammetry. Both methods give comparable although subtly different results. This data is evaluated alongside a review of field deployment issues to provide guidance to the community with respect to the factors which need to be considered in digital conservation of human/hominin footprints.
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Footprints are the most direct source of evidence about locomotor biomechanics in extinct vertebrates. One of the principal suppositions underpinning biomechanical inferences is that footprint geometry correlates with dynamic foot pressure, which, in turn, is linked with overall limb motion of the trackmaker. In this study, we perform the first quantitative test of this long-standing assumption, using topological statistical analysis of plantar pressures and experimental and computer-simulated footprints. In computer-simulated footprints, the relative distribution of depth differed from the distribution of both peak and pressure impulse in all simulations. Analysis of footprint samples with common loading inputs and similar depths reveals that only shallow footprints lack significant topological differences between depth and pressure distributions. Topological comparison of plantar pressures and experimental beach footprints demonstrates that geometry is highly dependent on overall print depth; deeper footprints are characterized by greater relative forefoot, and particularly toe, depth than shallow footprints. The highlighted difference between 'shallow' and 'deep' footprints clearly emphasizes the need to understand variation in foot mechanics across different degrees of substrate compliance. Overall, our results indicate that extreme caution is required when applying the 'depth equals pressure' paradigm to hominin footprints, and by extension, those of other extant and extinct tetrapods.
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The Las Cerradicas site (Tithonian-Berriasian), Teruel, Spain, preserves at least seventeen dinosaur trackways, some of them formerly attributed to quadrupedal ornithopods, sauropods and theropods. The exposure of new track evidence allows a more detailed interpretation of the controversial tridactyl trackways as well as the modes of locomotion and taxonomic affinities of the trackmakers. Detailed stratigraphic analysis reveals four different levels where footprints have been preserved in different modes. Within the tridactyl trackways, manus tracks are mainly present in a specific horizon relative to surface tracks. The presence of manus tracks is interpreted as evidence of an ornithopod trackmaker. Cross-sections produced from photogrammetric digital models show different depths of the pes and manus, suggesting covariance in loading between the forelimbs and the hindlimbs. Several features (digital pads, length/width ratio, claw marks) of some ornithopod pes tracks from Las Cerradicas are reminiscent of theropod pedal morphology. This morphological convergence, combined with the shallow nature of the manus tracks, which reduces preservation potential, opens a new window into the interpretation of these tridactyl tracks. Thus, trackmaker assignations during the Jurassic-Cretaceous interval of purported theropod trackways may potentially represent ornithopods. Moreover, the Las Cerradicas trackways are further evidence for quadrupedalism among some basal small- to medium-sized ornithopods from this time interval.
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This study concerns the formation, taphonomy, and preservation of human footprints in microbial mats of present-day tidal-flat environments. Due to differences in water content and nature of the microbial mats and the underlying sediment, a wide range of footprint morphologies was produced by the same trackmaker. Most true tracks are subjected to modification due to taphonomic processes, leading to modified true tracks. In addition to formation of biolaminites, microbial mats play a major role in the preservation of footprints on tidal flats. A footprint may be consolidated by desiccation or lithification of the mat, or by ongoing growth of the mat. The latter process may lead to the formation of overtracks. Among consolidated or (partially) lithified footprints found on present-day tidal flats, poorly defined true tracks, modified true tracks, and overtracks were most frequently encountered while unmodified and well-defined true tracks are rather rare. We suggest that modified true tracks and overtracks make up an important percentage of fossil footprints and that they may be as common as undertracks. However, making unambiguous distinctions between poorly defined true tracks, modified true tracks, undertracks, and overtracks in the fossil record will remain a difficult task, which necessitates systematic excavation of footprints combined with careful analysis of the encasing sediment.
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The narrow- and wide-gauge trackways attributed to sauropod dinosaurs are hypothesized to be a consequence of the relative positions of their centers of mass. This hypothesis was tested using three-dimensional, trackway-producing computer models of two sauropods and studies of Asian elephants. Centers of mass of sauropod models were computed using density distributions that reflect the high degree of pneumatization of the skeletons and air sacs within the body. A close correspondence was found between the relative areas of hand and foot prints in different trackways and the relative fractions of the body weight borne by the forefeet and hindfeet in the different types of sauropods inferred to have made the trackways. Experimental studies of Asian elephants corroborated the close correspondence between relative areas of the hindfeet and forefeet and body weight distribution. Replicating actual sauropod trackways with the walking models enabled testing of proposed gaits for a sauropod model. Brachiosaurus brancai, with its more centrally positioned center of mass, was stable and possessed a wide safety margin only when replicating a wide trackway. Conversely, Diplodocus carnegii, with a more posteriorly placed center of mass, was most stable when replicating a narrow trackway. A trend for large sauropods (>12 tons), independent of clade, to have more anteriorly positioned centers of mass was identified, and it is proposed that all large sauropods were restricted to producing wide-gauge trackways for stability reasons. The primitive gait state for Sauropodomorpha was determined to be one that produced narrow-gauge tracways.
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Two major ichnotypes of sauropod trackways have been described: "narrow-gauge," in which both manus and pes prints approach or intersect the trackway midline, and "wide-gauge," in which these prints are well apart from the midline. This gauge disparity could be the result of differences in behavior, body size, or morphology between the respective trackmakers. However, the biomechanics of locomotion in large terrestrial vertebrates suggest that sauropods were probably restricted in locomotor behavior, and the lack of systematic size differences between footprint gauges argues against body-size-related influences. We argue that skeletal morphology is responsible for gauge differences and integrate data from locomotor biomechanics and systematics with the track record to predict the hindlimb morphology of wide-gauge trackmakers. Broader foot stances in large, graviportal animals entail predictable mechanical consequences and hindlimb modifications. These could include outwardly angled femora, offset knee condyles, and a more eccentric femoral midshaft cross-section. A survey of sauropod hindlimb morphology reveals that these features are synapomorphies of titanosaurs, suggesting that they were the makers of wide-gauge trackways. The temporal and geographic distribution of titanosaurs is consistent with this hypothesis because wide-gauge trackways predominate during the Cretaceous and are found worldwide. Additional appendicular synapomorphies of titanosaurs are interpreted in light of identifying these animals as wide-gauge trackmakers. We suggest that titanosaurs may have used a bipedal stance more frequently than did other sauropods. These correlations between ichnology, biomechanics, and systematics imply that titanosaurs were unique among sauropods in having a more varied repertoire of locomotor habits.
Article
The narrow- and wide-gauge trackways attributed to sauropod dinosaurs are hypothesized to be a consequence of the relative positions of their centers of mass. This hypothesis was tested using three-dimensional, trackway-producing computer models of two sauropods and studies of Asian elephants. Centers of mass of sauropod models were computed using density distributions that reflect the high degree of pneumatization of the skeletons and air sacs within the body. A close correspondence was found between the relative areas of hand and foot prints in different trackways and the relative fractions of the body weight borne by the forefeet and hindfeet in the different types of sauropods inferred to have made the trackways. Experimental studies of Asian elephants corroborated the close correspondence between relative areas of the hindfeet and forefeet and body weight distribution. Replicating actual sauropod trackways with the walking models enabled testing of proposed gaits for a sauropod model. Brachiosaurus brancai, with its more centrally positioned center of mass, was stable and possessed a wide safety margin only when replicating a wide trackway. Conversely, Diplodocus carnegii, with a more posteriorly placed center of mass, was most stable when replicating a narrow trackway. A trend for large sauropods (>12 tons), independent of clade, to have more anteriorly positioned centers of mass was identified, and it is proposed that all large sauropods were restricted to producing wide-gauge trackways for stability reasons. The primitive gait state for Sauropodomorpha was determined to be one that produced narrow-gauge tracways.
Article
Tracks arise through a complex interplay between animal and substrate. Studying this dynamic process is challenging because most foot-sediment and sediment-sediment interactions are rapid and hidden from view. Herein, we describe a new method for visualizing and quantifying three-dimensional movements of both a morphologically accurate indenter and realistic sediment during track formation. Our method uses biplanar X-ray imaging and an animation-based workflow to reconstruct the trajectories of metal beads seeded throughout the sediment volume. X-rays allow sub-surface motion normally concealed by the foot and opaque matrix to be analyzed at 30 frames per second with sub-millimeter resolution. Results from two case studies of tridactyl tracks in semi-liquid mud provide novel, animated visualizations, examples of ensemble and particle-specific data, as well as measures of precision and accuracy. This methodology has the potential to mechanistically link specific track morphologies to foot movement, clarify undertrack formation, validate computational models, and set a new standard for evidence-based reconstruction of locomotion from fossil footprints.
The Purbeck Limestone Group (late Jurassic-early Cretaceous) contains a rich vertebrate trace fossil fauna. Research on this fauna has been almost entirely concerned with the dinosaur tracks. By contrast, the feeding traces and coprolites, which are occasionally abundant, have received little attention. The implications of some recent papers, including those where ichnotaxa were assigned, are considered along with the stratigraphic and geographic distribution of reptilian tracks. A plan of the principal footprint horizon at Townsend Road, Swanage, is presented and the more unusual aspects of the site illustrated. An appendix gives a comprehensive listing of published and manuscript accounts dealing with footprints from these strata. Some of the neglected feeding traces and coprolites are described and illustrated for the first time.
Article
The method of moire topography is suitable for three dimensional representation of dinosaur footprints. Using this method, we can project the contour-like lines directly on the surface of footprints. From moire pictures, it is possible to get numerical and topographical relief data and computer generated data perspective views. -Authors