Historical Biology

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Map showing Dakota Formation outcrop and subcrop in Nebraska, probable location of earlier, poorly documented find of ornithopod distal femur (Burt County), and dinosaur tracksite (southern Jefferson County). Exact locality information is being withheld to preserve site and protect private landowners.
Dakota Formation stratigraphy in Kansas and eastern Nebraska (left) and stratigraphy of dinosaur tracksite (right). Tracksite lies near middle of Dakota Formation between sequence boundaries D 1 and D 2 of Brenner et al. (2000).
A, Track number 20 (see Fig. 6), largest track at site, with three deep digit impressions that seem to show pad impressions. Scale in A, B, and C is 20 cm long. B, Same track with chalked outline. C, Similar large track (number 8) with deep digit impressions. D, Same track with chalked outline. Four digit impressions are shown, but the fourth, to the lower left, is very shallow and indistinct compared to the other three, which appear to be part of the same print. This track is probably two superimposed tracks, the fourth, shallow digit impression being older.
At least 22 tridactyl dinosaur tracks, poorly preserved in various degrees of expression, have recently been found at an exposure in the Dakota Formation (Lower Cretaceous, Albian) in Jefferson County, Nebraska. These tracks generally have broad, blunt digits and a broad posterior margin. The largest of the tracks measures 57 cm in length and 58 cm in width. All of the tracks lie within a stratigraphic horizon of 40 cm or less, but they do not form a single trackway. We interpret the trackmakers to have been ornithopods. The Jefferson County tracks are in a well-cemented sandstone with oscillation ripples, at a stratigraphic level between two well-established sequence boundaries. Channel forms and lateral accretion units are common in the stratigraphic interval enclosing the tracks, and the site is interpreted as a bar or sand flat in a tidally influenced river. The Jefferson County tracks are only the second known occurrence of large Mesozoic tetrapod tracks east of the Rocky Mountain Front-High Plains Margin, including the Black Hills of South Dakota, west of the Atlantic Coastal Plain, and north of the Gulf Coastal Plain. Further, this paper is the first documentation of in situdinosaur fossils from the Nebraska-Iowa area.
 
Dinosaur tracks and swimming traces have been discovered at three localities in the latest Albian Sarten Member of the Mojado Formation, Bisbee Group (="Anapra Sandstone"), at Cerro de Cristo Rey in Sunland Park, southernmost Dona Ana County, New Mexico. These localities preserve footprints of ornithopod (Caririchnium) and theropod (Magnoavipes) dinosaurs, ?reptilian swimming traces and possible tracks of an ankylosaurian dinosaur. The Sarten Member is of the latest Albian age, so the Cerro de Cristo Rey tracks are slightly younger than the well-known late Albian tracksites of northeastern New Mexico. At Cerro de Cristo Rey, the dominance of ornithopod tracks and absence of sauropod tracks fit regional patterns of late Albian-early Cenomanian track distribution consistent with North American extirpation of sauropods before the end of Albian time. The deltaic/coastal plain depositional setting of the Sarten Member is also remarkably similar to the track-bearing late Albian-Cenomanian sandstones of NE New Mexico, Oklahoma, Nebraska, and SE Colorado, which also have a tetrapod footprint ichnofacies dominated by ornithopod (Caririchnium) and theropod (Magnoavipes) tracks throughout the so-called "dinosaur freeway."
 
Mineralogical segregation of sand grains distinguishes the trace fossil Macaronichnus segregatis, which is composed of a felsic burrow infill with a mafic-and mica-rich burrow mantle. This study focuses on determining the mechanism by which M. segregatis trace-makers segregated mineral grains during deposit feeding. A modern opheliid polychaete, Euzonus mucronata, from Pachena Bay, Vancouver Island (Canada), was examined to explain the activities of their ancient counterparts. Microscopic videotaping of deposit feeding allowed for collection of data on ingestion and excretion through visual grain counts of felsic, mafic, and shell components. Normalization of these grain counts to the composition of the host sediment illustrates preferential ingestion of felsic grains over mafic. Shell fragments were generally avoided and visually mantled the burrows, obscuring the paucity of mafic grains in burrow infills. The avoidance of shell fragments is potentially a function of the large grain size, angular shape, surface texture, and/or associated low nutritive value. The preferential ingestion of felsic grains is attributed to en masse feeding in felsic-rich locales identified through sediment probing. This form of mineral segregation likely reflects the specific nature of the sediment and worm population. Accordingly, en mass deposit feeding in selected felsic-rich localities is one possible mechanism used in the construction of Macaronichnus segregatis and M. segregatis-like structures.
 
Assessing the temporal significance of invertebrate ichnofossils is essential in interpreting ancient organism behaviors, depositional settings, and bioturbation and sedimentation rates. The trace fossil, Macaronichnus segregatis, is known to represent the work of deposit-feeding polychaetes and commonly occurs as a pervasive structure in shallow-marine sandstone deposits. This study uses the polychaete Euzonus mucronata, which produces M. segregatis-like structures, as a modern analogue to the trace-making counterparts. Field measurements from Pachena Beach, Vancouver Island, Canada, included assessment of population densities and worm behaviors. Volumetric burrowing rates were obtained from a thin-walled aquarium constructed in the laboratory. The burrowing rate calculated for 5 Euzonus (0.089 cm3/hr) was extrapolated to populations (approximately 1,400-5,000 worms/m2) estimated from Pachena Beach, which require 70-300 days to completely rework 0.1 m3 of sediment. Calculated rates are dependent upon the limitations of simulating a natural setting in an aquarium, the population density assessment, and the particular characteristics of the worm population and foreshore at Pachena Bay. However, these initial estimates can still be applied to rock record examples such as the Macaronichnus segregatis found in the Appaloosa Sandstone of Alberta, Canada. In this unit, ancient worms persisted in dense populations and reworked sediment at a rate that exceeded deposition during overall foreshore aggradation.
 
Measured sections of the Dinosaur Canyon Member (keyed to Fig. 1) at Moenkopi Wash, Dinosaur Canyon and Tohachi Wash.
Features of P. tubularis in outcrop and hand specimen. A. Smooth-walled, cylindrical burrows assigned to the ichnospecies P. tubularis are weathering out of the eolian sandstone matrix near the top of the section at Tohachi Wash. B. The burrows clearly possess a smooth wall structure and a distinct lining that is ∼1 mm thick and lighter in color than the host rock. The burrow fill is identical to the host.
Features of rhizoliths horizons in eolian strata at Moenkopi Wash. A. The rhizoliths are branching and up to 10 cm in diameter. The sandstone host is bioturbated with mostly indistinct burrowing, but distinctive circular markings with positive relief (arrows) are assigned to P. gregarious. B. Rhizolith visibility is enhanced by calcite cementation and by bleaching of the rhizoliths interior. Locally, the interior of rhizoliths display an elongated gallery and chamber structure. C. The interior of most rhizoliths is calcite-cemented and bleached. In some instances, the bleaching extends diffusely into the host rock. At the top of the sandstone bed at 77 m, vertically oriented rhizoliths are closely packed. D. Rhizoliths with vertical to subhorizontal orientations are pervasive in this sandstone bed at 77 m in the Moenkopi Wash section.
Eolian strata of the Dinosaur Canyon Member (DC) immediately below conglomeratic Springdale Sandstone (Sp) are mottled and rhizolith-bearing, as seen here at Paiute Point. Arrows indicate densely packed rhizoliths and drab root traces.
The Dinosaur Canyon Member of the Moenave Formation, of Late Triassic to Early Jurassic (Rhaetian-Hettangian) age, consists predominantly of sandstones and mudstones deposited by sheet and channelized flow and by eolian processes. We document several previously undescribed biogenic structures in these strata. At one location, eolian dune sandstone hosts the lined, smooth-walled burrow Palaeophycus heberti (Saporta); these may be the nesting burrows of small sand wasps, or alternatively, the burrows of sand-treader camel crickets. Eolian dune facies that host abundant rhizoliths also are typically bioturbated. Circular markings that are convex in epirelief are assigned to Pustulichnus gregarious Ekdale and Picard. Unlined, non-ornamented burrows are unassigned. We speculate that both of these also were formed by the burrowing activity of one of the many species of sand wasp. Rhizoliths are particularly prominent at the tops of eolian dune sandstone beds and locally may host termite nests. Stabilization of the landscape by plants permitted pedogenic alteration of the sediments.
 
Geological map showing Jurassic outcrop distribution and the type localities of G. asturiensis and H. hauboldi associated with outcrops of the Tere nes Formation (modified from Garcia Ramos and Guiterrez Claverol, 1995). 
Views from above (A) and side (B) of a museum exhibit in the Natural History Museum in Dortmund, Germany which shows a giant tridactyl foot reconstruction depicting a theropod having just made the large track (replica of G. asturiensis from La Griega Beach, Asturias). The track is now interpreted as that of a sauropod. (See Color Plate VII) 
A: Map of the track-bearing surface at La Griega Beach locality, with Brontopodus trackway in black showing trackway width and tracing of last (distal) left manus-pes set (inset B—with star). H. h refers to the purported H. hauboldi paratype which we reject as a misidentified sauropod pes track. 
The type material of the ichnospecies Gigantosauropus asturiensis Mensink and Mertmann 198421. Mensink , H and Mertmann , D . 1984. “Dinosaurier-Fährten”. In (Gigantosauropus asturiensis n. g. n. sp.; Hispanosauropus hauboldi n.g. n. sp.), 405–415. New York: Academic Press. im Jura Asturiens bei La Griega und Ribadesella (Spanien). Neues Jarbuch für Geologie und Paläontologie Monatschefte, 1984 View all references is re-examined and shown to represent a sauropod rather than a theropod. This interpretation confirms the recent suggestions of several authors. We describe the trackway in detail but conclude that it is not diagnostic at any taxonomic level, below the general category of sauropod. Thus, G. asturiensis may legitimately be considered a nomen dubium, and the name should be restricted to the original material and not extended to formally describe other poorly preserved specimens. Claims that the largest pes tracks are 1.35 or even 1.5 m in length are incorrect. Pes length ranges from 98–125 cm (mean 110.75 cm). Hispanosauropus hauboldi Mensink and Mertmann 198421. Mensink , H and Mertmann , D . 1984. “Dinosaurier-Fährten”. In (Gigantosauropus asturiensis n. g. n. sp.; Hispanosauropus hauboldi n.g. n. sp.), 405–415. New York: Academic Press. im Jura Asturiens bei La Griega und Ribadesella (Spanien). Neues Jarbuch für Geologie und Paläontologie Monatschefte, 1984 View all references is also of doubtful utility as previously defined. The holotype, a field specimen, which clearly represents a theropod dinosaur, cannot be located, and may be lost to erosion. The paratype is a sauropod track and therefore has no relevance to the ichno-species description. Therefore, we select a new paralectotype and provide a more detailed description of specimens that can be assigned to this ichnotaxon. Hispanosauropus is similar to tracks recently described under the label Megalosauripus. However, the status of this latter ichnogenus, and the spectrum of track types to which it refers, is disputed. Thus, we provisionally restrict the name Hispanosauropus to the original illustrated holotype and a paralectotype from the same locality. On the grounds of morphological similarity, the name may be applied to similar material from elsewhere in the Upper Jurassic of Asturias.
 
In 1859 the French geologist Jules Desnoyers reported the discovery of vertebrate footprints in the Late Eocene gypsum of the Paris region. Although they attracted some attention at the time, those footprints were never illustrated or described in detail, and the present whereabouts of the specimens seem to be unknown. Several types of footprints were referable to animals known by skeletal elements from the gypsum, but some were not. Among the latter were tridactyl footprints of very large birds, which Desnoyers tentatively attributed to the giant ground bird Gastornis, which had been discovered in the Lower Eocene of the Paris region a few years earlier. Gastornithids are now known from the Paleocene to the Middle Eocene, but no skeletal remains of giant birds have yet been found in the Upper Eocene of Europe. The tracks of giant birds from the gypsum of the Paris region are thus an example of fossil footprints without known osteological counterparts, and the identity of the trackmakers remains an enigma.
 
Lingulide brachiopods have been important components of Phanerozoic marine ecosystems since the Paleozoic. Although lingulides developed an infaunal lifestyle early in their history, trace fossils attributed to their burrowing behavior have not been commonly recognized. Lingulichnus verticalis Hakes, the sole described lingulide-derived trace fossil, has been interpreted as a lingulide dwelling trace. Although modern lingulides engage in a wide variety of infaunal activities, including maintaining position during sediment aggradation (escape from burial) and reburial after erosional exhumation, ichnofossils reflecting these activities have not been previously recognized. Lingulide brachiopods and trace fossils reflecting the full spectrum of lingulide burrowing behavior (described herein) are common in Lower and Middle Triassic strata of western Canada. The description of Lingulichnus verticalis is revised to include spreitenate as well as simple vertical structures. L. inclinatus isp. nov. includes obliquely oriented forms. L. hamatus isp. nov. is described to include J- and U-shaped forms. Lingulichnus in the Triassic of western Canada occur in proximal offshore, offshore transition, lower shoreface, deltaic, estuarine and intertidal flat settings. The paucity of reports of Lingulichnus in the trace-fossil literature (and absence of reports of Lingulichnus in post-Triassic strata) is likely related as much to difficulties in recognizing these forms as it is to low preservation potential.
 
A newly discovered dinosaur tracksite in the Upper Cretaceous Dakota Group of southeastern Colorado preserves tracks attributable to ornithopod, theropod, and possibly ankylosaurid dinosaurs. Minimally 79 tracks occur at the site, and are comprised predominantly of ornithopod prints preserved as natural sandstone casts. Nine ornithopod tracks are preserved in situ, and all but one of these trends in a northeasterly direction. The high density of ornithopod tracks coupled with the similar trend of those in situ suggest gregarious behavior. Size distribution of the ornithopod tracks indicates that some juveniles are present, with sub-adults most abundant and lesser numbers of mature adults. Considerable size variation exists within the nine in situ tracks with similar trends. Thus, the site could record the passage of a mixed herd composed of several age classes. This may be the only reported Dakota tracksite where ornithopod, theropod, and ankylosaurid prints occur together.
 
Remnants of Bushmen cave paintings showing representations of dinosaurs evidently reconstructed from footprints, trackways and skeletal remains have been found in Lesotho. This is a region of prolific dinosaur trackways preserved in Lower Jurassic sedimentary rocks, and the Bushman culture is renowned for extraordinary skill in the tracking of modern animals. It is probable that the track and trackmaker representations depict ornithopod dinosaurs. The track drawings are accurate, and the trackmaker representations show that Bushman artists anticipated modern reconstructions of bipedal dinosaurs and produced depictions that are more realistic than many paleontological reconstructions that endured until quite recently.
 
Dinosaur tracks were first reported from the coal-bearing clastic sequences of the Ross River Block in 1999 by members of a University of Alaska Museum field party, and track sites were confirmed by a joint Alaska-Yukon team in 2000. This fault-bounded sedimentary block is 3 kilometers west of Ross River, in the Yukon Territory. The discovery was followed by two years of field mapping and collection. This research has resulted in the documentation of 251 individual tracks at two separate but stratigraphically related sites, as well as a short (four-footprint) trackway at one of the sites. Six ichnogenera were identified. Ornithomimipus, Amblydactylus, and Gypsichnites were recognized at one site. At a stratigraphically higher site, four ichnogenera were documented including Tetrapodosaurus, Irenesauripus, Amblydactylus, and Columbosauripus. This ichno-assemblage is compared with those of Aptian to Cenomanian age from Alberta, British Columbia, and Alaska. The discovery of unequivocal dinosaur evidence in a small structural inlier in the Tintina Trench that was previously assumed to be Eocene in age resulted in a restudy of the palynology and biostratigraphy of this coal-bearing sequence and the recent assignment of a middle Albian to early Cenomanian age to the upper part of the dinosaur-bearing interval.
 
Paleogastroliths, as defined in this study, are stomach stones associated exclusively with extinct animals. Definitive recognition of paleogastroliths is problematic and controversial. Polished, rounded stones found within skeletal remains of dinosaurs and plesiosaurs are the strongest evidence. This study examined intraskeletal and proposed paleogastroliths using a scanning electron microscope (SEM) to determine if any defining surface textures occur. Paleogastroliths associated with the skeletal remains of Seismosaurus hallorum, possible paleogastroliths from the Lower Cretaceous Cedar Mountain Formation, and other well-polished stones were obtained. Most stones were composed of either quartzite or chert and were examined with a SEM at magnifications ranging from 100× to 400×. All of the cherty Seismosaurus hallorum stones contained sets of parallel to sub-parallel, curved polish grooves that in places crosscut one another. These grooves are inferred to have formed as the result of small particles lodged in the stomach muscles interacting with the stones due to muscle movement. The distinctive surface textures noted on the cherty Seismosaurus hallorum paleogastroliths are similar to those seen on the cherty possible paleogastroliths from the Cedar Mountain Formation. Therefore, the geologic occurrence combined with the microscopic surface texture supports the interpretation that these stones are paleogastroliths.
 
In recent years, numerous dinosaur footprints have been discovered on bedding surfaces within the Lower Cretaceous Patuxent Formation of Maryland and Virginia. Among these, distinctive small tracks that display a combination of small manus with five digit impressions and a relatively much larger pes with four toe impressions evidently were made by animals belonging to the ornithischian family Hypsilophodontidae. These tracks differ from any ornithischian ichnotaxon previously described. We here name them Hypsiloichnus marylandicus and provide a description of their diagnostic characteristics. Although hypsilophodontid skeletal remains have not been found in the Patuxent, their skeletal remains are known from Lower Cretaceous strata of similar age in both western North America and Europe. Therefore, it is not surprising to find that an Early Cretaceous representative of this family also existed in eastern North America.
 
Sauropod footprints in the Uhangri Formation (Cretaceous) of Korea exhibit an unusual pattern of morphology, with the interior of each print partitioned into a series of pockets by conspicuous radial crests. The crests are evidently extramorphological features and have been interpreted as upwellings of sediment extruded through the floor of the footprint following its fracture by impact of the trackmaker's foot. That explanation entails some inconsistencies, and an alternative explanation is proposed here. The alternative explanation envisages delamination of a superficial sheet of sediment that was lifted into a canopy, which subsequently collapsed in radiating folds. The superficial sheet of sediment might have been lifted by either or both of two mechanisms—by adhering to the underside of the trackmaker's foot or by being forced upward into a blister-like dome by the backflow of water previously displaced by impact of the trackmaker's foot. These alternative explanations draw attention to minor morphological features that were previously unexplained.
 
Nine dinosaur ichnospecies from the Lower Jurassic to Upper Cretaceous of Japan, including two that are new, are described herein. The new ichnotaxa are Asianopodus pulvinicalx ichnogen. et ichnosp. nov. and Schizograllator otariensis ichnosp. nov. The Japanese ichnotaxa are allied to Lower Jurassic ichnospecies in South China, North America, Western Europe and South Africa, and Upper Jurassic to Lower Cretaceous ichnospecies from Southeast and East Asia. This suggests they were part of a global ichnofauna before continental drift began in the Middle Jurassic, leading to the development of a more endemic dinosaur fauna in the Cretaceous. At least two assemblages, an ornithopod-gracile-toed theropod-dominated community, in northeastern Asia, and a robust theropod- and sauropod-dominated community in the southern part of the continent, existed in the Cretaceous. This parallels North American dinosaur distribution patterns in the Cretaceous and seems to be a reflection of paleolatitudinal controls.
 
Invertebrate trace fossils are reported from the Late Triassic Chinle Formation at Ghost Ranch, New Mexico, for the first time. They occur in beds higher in the section than the Coelophysis Quarry. Six ichnotaxa are recognized: Steinichnus milfordensis, Planolites montanus, Palaeophycus tubularis, Taenidium serpentium, ?Arenicolites sp. and Skolithos sp. This ichnofauna is consistent with the Scoyenia ichnofacies, considered typical of lake margins in semiarid to arid regions.
 
The Reverend Henry Duncan (1774–1846), clergyman, philosopher, writer, politician, archeologist, poet, educator, social reformer, and the founder of savings banks, was indeed a “Man for All Seasons.” In 1824, while Minister of the Church of Scotland at Ruthwell, Dumfriesshire, Scotland, he was presented with a slab of red sandstone from the Corncockle Muir quarry in Annandale, exhibiting a set of footprints. Although Duncan felt from the start that he was dealing with the tracks of an animal, he wrote to the Reverend William Buckland, Reader in Mineralogy and Geology at the University of Oxford, to solicit his opinion on the origin of these curious markings. Buckland was at first skeptical but, after receiving casts of the markings from Duncan, he became convinced that they did in fact represent footprints, urging Duncan to study and publish on what he considered to be a very important paleontological find. On January 7, 1828 Duncan described the Corncockle Muir footprints to the Royal Society of Edinburgh and quoted Buckland's findings. Duncan's paper was not published by the Society until 1831, but it aroused considerable interest and was reported in several newspapers. This represents the first scientific report of a fossil track.
 
Cumulative bioerosion publications since 1850 showing the rise of research efforts in the field. Bioerosion as a process first defined by Neumann (1966). Bibliographic data from Wilson (2004) includes bioerosion publications prior to the formal naming of the process. Publications for the 2003–2004 interval are incomplete. 
The First International Bioerosion Workshop held in 1996 provided a forum for an increasing interest in bioerosion research and helped foster convivial relations among researchers in this specialization. The current trend in bioerosion publishing is positive and will be aided with consolidated efforts to attract both new recruits and grant awards. Contributors of the Fourth IBW in Prague decided to hold the next meeting in Erlangen, Germany.
 
Many attempts have been made by ichnologists to match bioerosion traces to their respective tracemakers. This task has been considered difficult, especially for fossil samples. The present study demonstrates that the Australian bioeroding sponge Aka paratypica can generate a cavity similar to the ichnospecies Entobia devonica. The modern sponge and its cavity are redescribed and compared to the fossil boring. A. paratypica has white fistules and soft, mucoid endosomal tissue. Spicules are stout oxeas with often telescoped or mucronate tips. Observed borings of A. paratypica are rounded and cavernous, with canals and apertures radiating from the chambers in all directions. It was noted that the internal openings of such canals are covered with porous nodules, which may act as sieves against larger particles or intruding endofauna. No obvious microsculpturing was observed in the erosion scars. A. paratypica borings are analogous to ancient E. devonica borings, which to date were only known from the fossil record.
 
Dolomitized burrows in the Mississippian (Visean) Debolt Formation of northwestern Alberta, Canada form the primary reservoir intervals in the Dunvegan gas field. Sedimentological and ichnological analyses suggest a carbonate ramp setting that includes subenvironments such as sabkhas, hypersaline lagoons, restricted subtidal lagoons, intertidal mud flats, and peloidal shoals. Dolomitization occurs primarily within oxidized muds and highly bioturbated sediments, with the primary mode being sabkha-associated precipitation. In this context, dolomitization within the burrows also appears to be mediated by sulfate-reducing bacteria. δ18O values for dolomite within burrows (mean 2.4‰) are enriched by 1.3‰ relative to calcite values (mean 1.1‰) within the burrows. This degree of fractionation is similar for dolomite and calcite that have precipitated from the same solution. It is therefore suggested that the protodolomite precipitated in equilibrium with calcite rather than by replacement of pre-existing calcite. Isotopic values of δ13C measured for dolomite associated with burrows (mean 3.4‰) and matrix (mean 3.5‰) is slightly enriched relative to measured calcite values (mean 3.2‰ for matrix; mean 3.1‰ for burrows). These isotopic trends are common for modern dolomite that has precipitated in equilibrium with seawater where concomitant sulfate reduction and organic carbon-oxidation is inferred to occur near the surface.
 
Crocodylians are known to consume and modify bones, but actualistic observations of their bite marks have been limited to forensic case studies and surveys of two taxa: Crocodylus niloticus and Crocodylus porosus. To further explore patterns of crocodylian bite mark expression, we conducted a survey of traces left by Alligator mississippiensis. We compared the results to pre-existing crocodylian datasets regarding the potentially diagnostic traits of bisected marks, hook scores, and a lack of furrows. Mark type did not correlate with vital statistics of the sampled animals or collections protocol. Bisected marks were found in rates similar to those seen in one previous survey of C. niloticus, and rates of hook scoring and bone breakage were higher. These traces were all present in higher rates than those reported in C. porosus. Unlike results seen in Crocodylus, furrows were identified in the A. mississippiensis samples. Hook scores were also identified, but recent surveys of non-crocodylian taxa have shown that these features are not unique to crocodylians and instead are related to inertial feeding strategies. The presence and rate of bisected marks found in this study bolster the interpretation that these traces are a clade-wide phenomenon and a useful diagnostic indicator for Crocodylia.
 
Footprint measurements. (A) Individual measurements for single footprints. (B) Trackway parameters.
Overview of the tracksite. (A) Map of trackways. (B) Outline drawings of best preserved single footprints.
T1
Until now dinosaur tracks from Switzerland were only known from Triassic and Late Jurassic strata. We report here for the first time the occurrence of ornithopod tracks from the Schrattenkalk Formation (Late Aptian) from the Swiss Central Alps. The locality is situated in an abandoned quarry on the shore of Lake Lucerne close to the village of Beckenried. The steeply inclined surface has more than 50 tracks (in three trackways) of ornithopod dinosaurs that are attributed to iguanodontids. Three trackways can be followed for distances of 25 to 35 m. The lengths the footprints (mean: 30 cm) point to animals ranging in size of from 4 to 6 m, with estimated hip heights between 1.8 and 2 m (hip height 6 FL) and 1.4 to 1.7 m (hip height 5 FL). One of the trackways shows two succesive manus impressions, indicating facultative quadrupedal gait. The track bearing layer consists of shallow water micrites with traces of emersion, and it is overlain by bioclastic grainstones. Previously the Upper Schrattenkalk Member in the Helvetic realm was thought to have formed on a large shelf far away from any continents. The present discovery will shed new light on the paleogeographic position of the Helvetic nappes.
 
A new ichnotaxon is described from the Lower Jurassic (Upper Hettangian-Lower Sinemurian) carbonate tidal flats on the central-eastern Italian Alps. The narrow-gauge trackway is that of a large quadrupedal dinosaur. The pes is functionally tetradactyl with three rounded antero-medially directed digits, and the manus is pentadactyl. This quadrupedal form is close to Otozoum and Pseudotetrasauropus jaquesi both traditionally related to sauropodomorph trackmakers. The similarity with Otozoum is so marked that Lavinipes and Otozoum could be cogeneric. But the overall evidence today is that the Otozoum trackmaker was generally bipedal, whereas the trackmaker of L. cheminii is fully quadrupedal. The manual prints of L. cheminii show five short clawless digits and are different from the tetradactyl slender toed manual prints of Otozoum. The possible sauropodomorph affinity of the L. cheminii trackmaker is here discussed with an attempt to a revision of the Late Triassic-Jurassic tracks which have been traditionally related to sauropod and prosauropod.
 
Mammal tracks from the latest Cretaceous (Campanian-Maastrichtian) of Colorado are described as Schadipes crypticus ichnogen. et ichnosp. nov., on the basis of material from the Laramie Formation in Golden, eastern Colorado. This ichnospecies, and a closely related form (Schadipes sp.) from the Mesaverde Group of western Colorado, represent the only mammal tracks so far identified from the Upper Cretaceous. A possible mammal track from North Africa (Agadirichnus elegans) was originally attributed to a lizard/lacertilian. Other purported Lower Cretaceous mammal tracks are based on isolated specimens of materials that are dubious or as yet undescribed in detail. Morphologically, Late Cretaceous mammal tracks resemble those of some modern rodents. However, based on the dominant mammalian elements of faunas at that time they are probably of marsupial or multituberculate affinity.
 
Trackways described as Batrachopus (Batrachopodidae Lull, 190426. Lull , R. S. 1904. Fossil footprints of the Jura-Trias of North America. Memoirs of the Boston Society of Natural History, 5: 461–557. View all references) from the Lower Jurassic of Europe are rare and in some cases different from the type trackways from North America. Differences may be in part attributable to preservation, but current evidence suggests that there is inherent variability in Batrachopodidae morphotypes, beyond that attributable to differential preservation. Type Batrachopus is a stout-toed form, with minimal digit divarication (i.e., a long foot), whereas Antipus describes slender-toed forms with a wider foot and wider digit divarications. Antipus is also similar to Crocodylopodus (ichnofamily Crocodylopodidae: Fuentes Vidarte and Meijide Calvo, 19997. Fuentes Vidarte , C. and Meijide Calvo , M. 1999. Primeras Huellas de Cocodrilo en el Weald de Cameros (Sria, Espana) Nueva Familia Crocodilopodidae: Nuevo icnogenero: Crocodylopodus Nueva icnoespecie: C. meijidei. Actas de las jornadas internacionales sobre paleontologia de dinosairios y su entorno. Sala de los infantes (Burgos, Espana). Collectivo Arqueologico-Paleontologico de Salas, : 329–338. View all references) from near the Jurassic-Cretaceous boundary in Spain. Crocodylopodus has a relatively large manus, and a less outwardly rotated trackway, but is not sufficiently different from Batrachopodidae to warrant its own ichnofamily. Manus-pes size (area) ratios (heteropody) may also be important in differentiating different crocodylomorph ichnotaxa, as is the case with other archosaurian ichnotaxa. However, heteropody may change with size, and be less pronounced in large individuals. Manus and pes rotation patterns, and trackway width are variable and may be of use for differentiation of ichnotaxa but may also be a function of speed.
 
Since classical times and earlier, footprints in stone have intrigued humanity. Sometimes the supposed footprints were mere indentations produced by the chances of erosion; sometimes they were invertebrate fossils; and sometimes they were faked; but quite often they were the tracks of extinct creatures. The interpretations resulting from observations of these phenomena included legends of gods, heroes and saints: but, on occasion, the envisioning of the track‐maker was remarkably accurate. This account of the folklore of footprints surveys legends from Europe, North and South America, Africa and Australia; it concludes with the beginning of their scientific observation.
 
We describe intergradations between the arthropod repichnial trace fossils Diplichnites gouldi (Gevers et al., 1971), Dendroidichnites Demathieu et al., 1992, and Monomorphichnus Crimes, 1970 with two distinct cubichnial traces, Gluckstadtella cooperi Savage, 1971 and Huilmuichnus santracruzensis new ichnogenus and ichnospecies. These compound ichnofossils are part of high ichnodiversity arthropod-dominated trace fossil associations from the Late Carboniferous Agua Escondida Formation of the San Rafael Basin (Argentina). The complex ichnotaxonomy of Diplichnites and the ichnospecies D. gouldi are discussed and some possible working solutions are proposed. The most likely producer of the compound trace fossils are the Pygocephalomorpha, a group of Late Paleozoic crustaceans that are recorded in nearby basins from Uruguay and Brazil. The compound trace fossils are used to infer a number of complex behaviors of pygocephalomorphs in a subaqueous setting, including caridoid (tail flip) or more primitive escape reactions, landing followed by resting and transient resting during normal walking. In addition, different gaits can be inferred from well-preserved D. gouldi, which can be correlated with contrasting trackway morphology.
 
A diverse assemblage of dinosaur and bird tracks from Niobrara County, Wyoming, represents the first vertebrate ichnofauna reported from the bone-rich Lance Formation (Maastrichtian, Upper Cretaceous). The ichnofauna includes a hadrosaur track with skin impressions; three theropod track types, including the tetradactyl track Saurexallopus zerbsti (ichnosp. nov.); a tridactyl dinosaur footprint with a fusiform digit III; possible Tyrannosaurus tracks; four distinctive avian ichnites; and invertebrate traces. The footprints are generally well-preserved and so offer a unique insight into the ecology of a small river valley during the Maastrichtian.Saurexallopus zerbsti ichnosp. nov. from the Lance is similar to Saurexallopus lovei recently reported from the Maastrichtian, Harebell Formation, of northwestern Wyoming, but is represented by much better material, facilitating amendment of the ichnogenus. Skeletal equivalents for Saurexallopus are not currently known. Similarly, the tridactyl track with fusiform digit III is similar to footprints reported from the coeval Laramie Formation of Colorado and may also be similar to ichnogenus Ornithomimipus from the Edmonton Group of Alberta (though not necessarily of ornithomimid affinity). The hadrosaurian track with the skin impression is reminiscent of a similar ichnite reported from the Maastrichtian, St. Mary River Formation in Alberta, which is herein named Hadrosauropoduslangstoni as part of a reassessment of Cretaceous ornithopod track ichnotaxonomy. Such correlations demonstrate the utility of tracks for local or regional biostratigraphy (palichnostratigraphy) in western North America. It is also clear that tracks add to our knowledge of the composition and distribution of dinosaurian and avian components of Maastrichtian faunas. In particular the bird tracks indicate a diversity of at least four species, one of which was a semi-palmate form, hitherto unknown in the ichnological record and named Sarjeantichnus semipalmatus.
 
A number of benthic diatoms (including species of the genera Cocconeis, Achnanthes, and Amphora) etch shallow attachment scars in carbonate hard substrates. The morphology of these microbioerosion traces mirrors the elliptical to biconvex outline of the diatoms, which, in its most common appearance, is expressed as a distinct ring-shaped groove. The traces are established as new ichnogenus and -species Ophthalmichnus lyolithon. The diatoms are assumed to form the etching scars by means of their adhesive mucilage composed of acidic polysaccharides, probably in order to enhance adhesion.
 
A dinosaur footprint assemblage from the Lower Jurassic Ziliujing Formation of Zigong City, Sichuan, China, comprises about 300 tracks of small tridactyl theropods and large sauropods preserved as concave epireliefs (natural molds). The theropod footprints show similarities with both the ichnogenera Grallator and Jialingpus. Three different morphotypes are present, probably related to different substrate conditions and extramorphological variation. A peculiar preservational feature in a morphotype that reflects a gracile trackmaker with extremely slender digits, is the presence of a convex epirelief that occurs at the bottom of the concave digit impressions. It is possibly the result of sediment compaction underweight load when the pes penetrated the substrate, being a resistant residue during exhumation and weathering. The sauropod tracks belong to a trackway with eight imprints consisting of poorly preserved pes and manus tracks and a better preserved set, probably all undertracks. The narrow-gauge trackway pattern resembles the ichnogenus Parabrontopodus well known from the Jurassic but other features such as the minor heteropody are different. The assemblage enriches the dinosaur record from the famous Zigong locality and the evidence from the Lower Jurassic in this area that was restricted to a few skeletal remains and footprints. Furthermore it proves the presence of small theropods, whereas skeletons of the group, well- known from the Middle-Upper Jurassic of Zigong, are of medium to large size only. Remarkable is the dominance of saurischians in these assemblages, which is characteristic of Jurassic dinosaur communities whereas the Cretaceous record shows an increase of ornithopod groups. An overview of the dinosaur trace and body fossil record of the Sichuan Basin supports this view. The paleoenvironment can be designated as a low-latitude tropical freshwater lake as it is indicated by bivalve shells.
 
The enigmatic ichnogenus Selenichnus (Hitchcock, 185812. Hitchcock , E. 1858. Ichnology of New England, a report on the sandstones of the Connecticut Valley, Especially its fossil footmarks, 220Boston: William White. View all references) from the Lower Jurassic of Massachusetts and Utah may represent poorly preserved, extramorphological examples of Batrachopus. Selenichnus trackways from the St. George area (Utah) are virtually indistinguishable from the type material described by Hitchcock (1858)12. Hitchcock , E. 1858. Ichnology of New England, a report on the sandstones of the Connecticut Valley, Especially its fossil footmarks, 220Boston: William White. View all references and Lull (1953)20. Lull , R. S. 1953. Triassic life of the Connecticut Valley. Bulletin of the Connecticut State Geology Natural History Survey, 181: 1–331. View all references from Massachusetts. However, Selenichnus type specimens from Massachusetts, as well as the material from Utah, suggest a relationship with Batrachopus: The former track morphology appears to transform into the latter as preservational conditions change. The size and gait indicated by the two ichnogenera are similar. The suggested relationship between the two ichnogenera does not alter the fact that there are distinct differences in the morphology of the type specimens. Thus, pending discovery of more material, formal synonymy of the two ichnogenera is not formally proposed.
 
Therangospodus oncalensis is a Berriasian theropod ichnotaxon from the Cameros Basin (Soria Province, Spain). We discovered new trackways assigned to this ichnotaxon during cleaning and conservation works at the type locality (Fuentesalvo), enabling us to describe it more precisely. Therangospodus oncalensis was made by a medium-sized theropod dinosaur and is characterized by a single tapering pad on each toe, a rounded heel impression and a narrow trackway. In addition to having similar morphometric characteristics, most of the trackways at the Fuentesalvo site show comparable size and biometric features. This indicates that, in terms of size and age, a homogeneous population of a single theropod species could have produced these tracks. Moreover, the similar orientation (lying within a range of only 15°) and estimated speed suggested by most of the trackways, lend weight to the hypothesis that the trackmaker of Therangospodus oncalensis was able, at least at times, to move in structured packs displaying gregarious behaviour. Furthermore, this is the first structured pack of theropods to be described.
 
Anterior or cranial view of an adult Caiman during stance and locomotion. Heavy vertical line or reference axis between the pectoral girdles shows the position of the midline. When stationary (A), the forelimbs can assume a sprawled position with the upper arm horizontal and the lower arm at right angles. In this stance, center of the manus is about 13 cm lateral from the reference axis. Contrast this with the semi-erect stance (B), where the upper arm moves through an anterior-posterior arc that is about 60 • below horizontal. The lower arm, however, remains approximately vertical. In this semi-erect stance, the supporting manus is about 6.5 cm from the midline. Lateral movement of the body is visible in this sequence (C, D), with the total distance (dashed arrow) of about 5 cm, or 7% SVL. Scale in cm.
Two trackways made by the same 130 cm Caiman across mud (see text) (A, B). The midpoint of the manus prints are about 13 cm apart, or about 6.5 cm on each side of the trackway midline. Arrows indicate tail drag marks. Note that the manus tracks are slightly medial to the midline of the pes tracks.
Lateral motion of the body as seen in higher quadrupedal vertebrates serves to keep the center of mass nearer the weight-bearing legs as also occurs in the Caiman (FIG. 1): (A) Canis familiaris (drawn from video); (B), Elephas maximus (drawn from Muybridge, 1957, pl. 111, frames 1 and 12).  
Trackways record animals in motion, not stationary. Therefore, assumption of an erect stationary stance for Triceratops (A) from a Ceratopsipes trackway, assumes no lateral motion of the body, which would bring the center of gravity closer to the weight bearing limb (compare Caiman trackway of Fig. 2A, B, with anterior view of Caiman walking in Fig. 1B–D). Furthermore, in light of the Caiman locomotion, the prediction that a semi-erect stance in Triceratops would produce wider manus tracks than pes tracks (B) is incorrect (modified from Lockley and Hunt, 1995). It is also erroneous to assume no influence of lateral motion in sauropod locomotion and the resulting trackways. It is possible that wide gauge tracks (C) were made by a taxon that had less lateral motion than the maker of the narrow gauge tracks (D). See also Fig. 5. (Modified from Wilson and Carrano, 1999).  
Influence of lateral motion during locomotion is apparent in the overlay of the adult Caiman trackway (heavy lines; traced from Fig. 2A) on (A) the sauropod trackway Brontopodus (light lines; modified from Farlow, 1987) and (B) the alleged ceratopsian trackway Ceratopsipes (light lines; modified from Lockley and Hunt, 1995). All are to the same pes length. Note that the tracks coincide fairly well, yet the Caiman is known to walk semi-erect and to have significant lateral body movement (see Fig. 1).  
Locomotion in the alligatorids Caiman and Alligator show ontogenetic changes in gait width, manus orientation, and the amount of lateral body movement. In addition, the trackway of an adult Caiman is narrower than predicted for a semierect position of the limbs based on stance. The narrowness of the Caiman trackway is due to lateral movement of the body during locomotion. This movement allows placement of the feet closer to the trackway midline than would occur if no lateral bending occurred. Lateral movement is widespread among limbed tetrapods, yet little consideration has been given to its effects in trackmaking. Inferring stance from fossil trackways must take into account lateral body movement, otherwise the resultant hypothesis will be flawed.
 
Images of shell microborings in Elliptio complanata (Unionoida). A. Diagrammatic view of exterior surface of left valve, showing location of umbo (U) and radial section illustrating dorsal-ventral alignment of prepared and examined section, in addition to approximate locations for images B-H (arrowed). B?H. Scanning electron microscopy images of the nacreous shell layer. B. Exterior planar surface view of exposed nacreous layer in umbonal region, illustrating density and distribution of microborings. C. Characteristic c-axis alignment of microborings, penetrating through and normal to multiple nacre tablets in a fractured radial section of the bivalve. D. Fractured radial section of Elliptio complanata demonstrating an inclined microboring alignment . E. Planar view showing relationship between microboring and surface of nacre tablet. F, G. Detail views from within image B, showing variation in cross-sectional morphology of the microborings and their lining ornamentation . H. Detail of ornamentation of interior within microboring (note sinuous furrowing indicated by arrow). Scale bars: A D 1 cm; B D 10 mm; C?H D 1 mm.  
Diagrammatic representation of unionid shell structure, indicating the relative positions and orientations of each shell layer. Upper images depict the shell shape in lateral view (top right) and apical plane cross-sectional view (top left), and the pale grey line A?B denotes the line of section. U D umbo. The line surrounding the umbonal region, depicted in the top right figure approximately demarcates the umbonal area affected by loss of the exterior periostracum layer, with predominantly intact periostracum occurring across the rest of the shell surface. Scale bar for both images D 1cm. In the lower cross sectional view (bottom) where B?C denotes the line of section, black regions represent areas of organic proteinaceous conchiolin and white areas represent crystalline aragonite. From the shell exterior, progressing inwards; P D periostracum, composed of conchiolin; PR D prismatic aragonite layer; N D nacreous aragonitic layers; C D conchiolin. The lower cross sectional view is a representative image and doesn't illustrate the prolific number of nacre layers, which is typically an order of magnitude higher than depicted here. Lower cross sectional view not to scale.  
Scanning electron microscopy images of the nacreous interior shell layer of Elliptio complanata (Unionidae), illustrating microboring. Moderate chemical etching of nacreous aragonite tablets is also apparent. A, B. Overview images showing density and random orientation of microboring features. Note local sheets of extracellular polymeric substance and coalescing fibrous organic material, orientated parallel or at low angle to the shell interior and often found in association with borings. C?F. Detailed views of borings penetrating nacreous aragonite tablets. The lining , surface texture, prevailing orientation parallel or at a low angle to the shell interior and the presence of branching (E) and coalescing (F) are readily apparent. Scale bars D 10 mm.  
Scanning electron microscopy images of microboring affecting an organic conchiolin layer within the nacreous shell layer of Elliptio complanata (Unionidae) exposed at the shell surface by taphonomic decay illustrated in Figure 2. A. Progressive degradation of the surface is observed, from unaltered material (left) through an irregular polygonal ridge network (centre) to a continuous , smooth, irregular extracellular polymeric substance (EPS) dominated biofilm surface (right)(Inset box marks location of 5B). B. Detail of boundary between moderately (left) and heavily degraded shell material, in which loose nacreous aragonite tablets are enveloped in EPS (right) (Inset box marks location of 5C). C. Detail of ridge network. Dislodged nacreous aragonite tablets are clearly visible, together with localized EPS (Inset box marks location of 5D). D. Detail of fibrous EPS, similar to examples illustrated in Figure 6. Scale bars A?C D 10 mm, D D 1 mm.  
Samples of the unionid bivalve Elliptio complanata were collected from the channel of the freshwater Saint John River, from Fredericton, New Brunswick, Canada. Scanning electron microscopy imaging of prepared shell samples revealed an assemblage of microborings. No borings are noted on the periostracum or prismatic shell layers. Boring structures are instead confined to the underlying nacreous aragonitic shell material, together with its associated organic conchiolin layers. Three main styles of boring are encountered, encompassing both predominantly surficial structures and penetrative tubular borings. Surficial structures are represented by a polygonal network on an exposed conchiolin shell layer. The penetrative borings take two forms, one being simple unbranched tubes, steeply aligned (perpendicular to the shell surface) and traversing the full thickness of the nacreous shell layer. The other penetrative boring style, again occurring within the nacreous layer, comprises a complex irregular network of randomly oriented rarely branching tubular borings. Borings generally display diameters of micron scale. Biofilm and extracellular polymeric substances, with bacterial, diatomaceous and filamentous components are also observed, often displaying a close association with both the borings and the conchiolin layers within the shell. The formation of the borings may be attributed to cyanobacteria, cyanophyte or fungal progenitors.
 
The most recent account of Bueckeburgichnus maximus Kuhn 1958, a distinctive theropod dinosaur track from the Lower Cretaceous of Germany, is shown to be based on a referred specimen mistakenly identified as the holotype and the correct name of this taxon is deemed to be Megalosauripus maximus (Kuhn 1958). This minor revision has important consequences for nomenclature of the many European, Asian, North American and Australian dinosaur tracks attributed to megalosaurian theropods. Many of those tracks were named Megalosauripus, but that name has a confusing multiplicity of meanings and it should be restricted to the highly characteristic dinosaur track formerly identified as Bueckeburgichnus. Other tracks named "Megalosauripus”; (in its several other senses) will require new nomenclature, despite their extensive and repeated revision since 1996. It is recommended that future revision should adopt conventions of the International Code of Zoological Nomenclature. Although previous revisions expressed an intention to adhere to those conventions, these were not put into practice, with the unfortunate result of multiplying the problems that surround the nomenclature of megalosaur tracks. Introduction of the name Megalosauripus maximus (Kuhn 1958) eliminates those burgeoning problems and permits the introduction of new and objective nomenclature for presumed megalosaur tracks.
 
A test of the Lower Paleocene holasteroid echinoid Echinocorys ex. gr. scutata Leske from Göynük, Turkey, preserves a Planolites beverleyensis (Billings) burrow close to the internal surface. Identification of such a specimen is fortuitous; only where the test has broken cleanly away from the internal mould can such burrows be exposed, if present at all. A second specimen, from the Upper Cretaceous of Norfolk, England, bears a sinuous boring identified as Planolites montanus Richter.
 
In September 2001, large ornithopod footprints were found in the Nemegt Formation at the locality known as Nemegt in the Gobi of Mongolia. Additional hadrosaur ichnites, plus footprints of sauropods and theropods, have been recovered since then. The Nemegt Formation is known for the number and diversity of dinosaur skeletons found there, but footprints have never before been reported. Footprints were noted in three horizons within the formation, and occur at the top of upward-fining successions of floodplain sandstones and mudstones of a meandering fluvial paleoenvironment. Most of the footprints are preserved as natural casts that show good preservation of detail. Skin impressions are found on some, and many have slide marks. The vast majority of the footprints can be identified as having been made by Saurolophus, but two footprints each of Tarbosaurus and Opisthocoelicaudia were also recovered. Three hadrosaur footprints were found in the quarry of a Tarbosaurus skeleton. It appears that after the Tarbosaurus had died and been partially buried, its skeleton was trampled by a hadrosaur. The overwhelming domination of hadrosaurs at the footprint levels suggests there are preservational biases acting on the fossilization of Nemegt skeletons to produce abnormally high predator/prey ratios.
 
Tracks and traces of crouching theropods are rare, known from only three specimens from the Lower Jurassic of New England and the Lower to ?mid Jurassic of China. The New England specimens reveal manus, metatarsal and sub-crescentic ischial callosity impressions associated with Grallator-like tracks. The Chinese traces reveal metatarsal traces and a sub-triangular ischial callosity impression associated with Eubrontes-like tracks. All reveal symmetrical crouching postures. Theropod crouching traces should not be confused with ornithopod crouching traces, often assigned to Anomoepus. The ichnotaxonomy surrounding all these traces and associated footprints is very complex, and over split. Suggestions for simplification allow recognition that the North American and Chinese ichnofaunas have many similarities. The ichnotaxonomy is not as complex and confused as it may at first appear.
 
Much has been discovered about the movement speed of extant animals through the use of a variety of instruments, but much less is known about the speeds of extinct animals. The anatomy and mobility of prehistoric animals can be deduced from their bone remains and ichnofossils. By the use of biomechanics, their movement speeds also can be determined. Many ichnofossils have been found at Ipolytarnóc (the Miocene footprint locality at Ipolytarnóc, Hungary.) Ichnofossils of the most studied mammals from this site have been used in this study: the herbivores Rhinoceripeda tasnadyi, Megapecoripeda miocaenica, and Pecoripeda hamori, and the carnivore Mustelipeda punctata. The movement speed of each species was calculated from its foot and stride lengths. At Ipolytarnóc, Rhinoceripeda tasnadyi was able to move with a speed of 4.29 m/s, while Megapecoripeda miocaenica could reach a speed of 3.01 m/s. In the case of Pecoripeda hamori, its speed was 4.53 m/s, while in the case of Mustelipeda punctata it was 2.05 m/s. Conclusions about the paleoenvironment and the movement speeds of the prehistoric animals are based on our results. At times, the ancient mammals of Ipolytarnóc wallowed in puddles and muddy pools.
 
A complex microboring trace of fungal affinity is described in shells as a new ichnotaxon Saccomorpha stereodiktyon isp. nov. and compared with the earlier established ichnotaxon Saccomorpha terminalis Radtke, 1991. The new trace is characterized by a three-dimensional network of tunnels composed of a bifurcate horizontal (parallel to substrate surface) network with an upright (perpendicular to surface) system of tunnels and by the formation of cylindrical to multilobate terminal sporangial swellings. The new trace shares with Saccomorpha terminalis Radtke, 1991 the terminal position of sporangial swellings but differs from this ichnotaxon by its complexity in spatial arrangement, segmented construction, and ramification of tunnels. The horizontal parts of the network in the new taxon adhere to the substrate surface and regularly produce thinner tunnels that explore the interior of the substrate, allowing the producer to participate in digestion of organic lamellae incorporated in the shell. Microborings similar to the new trace fossil have been observed in modern bivalve shells of the Atlantic Ocean, North Sea, Adriatic Sea and Red Sea at depths ranging from the intertidal down to 1,550 m. The fossil record of the trace reaches back to the Jurassic and the type material stems from a Lower Oligocene oyster shell. The study shows that complex microboring traces reflect both behaviour and developmental strategy of their makers.
 
The tracks ascribed to pterosaurs from the Late Jurassic limestones at Crayssac, France, must be pterosaurian because the manus prints are so far outside those of the pes, the pes print is four times longer than wide, and the manus prints appear to preserve distinct traces of a posteromedially directed wing-finger. These tracks are different in important ways from previously described Pteraichnus trackways, which have been variably considered pterosaurian, crocodilian, or indeterminate. No Pteraichnus (sensu stricto: those not from Crayssac) tracks have diagnostic features of pterosaurs and in none can a complete phalangeal or digital formula be reconstructed; however, all published Pteraichnidae tracks fulfill the criteria of poor preservation, and some have some diagnostic features of crocodile tracks. Reconstructions of pterosaurs walking in pteraichnid tracks do not fit those tracks well, but crocodiles do. In contrast, the Crayssac tracks demonstrate the erect stance and parasagittal gait previously reconstructed for pterosaurs. They also demonstrate that the footfall pattern was not as in typical reptiles (LH-RF-RH-LF), but that the manus must have been raised before the next forward step of the ipselateral foot (LH-LF-RH-RF), suggesting that the quadrupedal pattern was secondary. The metatarsus in pterosaurs was set low at the beginning of a stride, as it is in crocodilians and basal dinosaurs. The diagnosis of the Ichnofamily Pteraichnidae comprises features of possible crocodilian trackmakers, but not of possible pterosaurian trackmakers. Trackways considered for attribution to pterosaurs should show (1) manus prints up to three interpedal widths from midline of body, and always lateral to pes prints, (2) pes prints four times longer than wide at the metatarso-phalangeal joint, and (3) penultimate phalanges longest among those of the pes.
 
The many faces of footprints of shod humans. ( A ) The footprint from a stiletto heeled shoe is able to leave puncture marks from the heel in even hard substrates. ( B ) Parallel meandering traces in snow produced by humans wearing skis. ( C ) Apparent didactyl human footprint produced by ( D ) RGB in Japanese free-toed boots. ( E ) Footprint in beach sand from a human wearing fins. If found fossilized, this could be described as the footprints from an aquatically adapted species of human. All photos by RGB. 
Incorporating footprints from shod humans into ichnotaxonomical nomenclature presents several problems in that the track maker does not actually touch the sediment, and further the wear of shoes represents a behavioral choice as well as evidence of technological developments in shoemaking. If footprints of shod humans were to be treated ichnotaxonomically, they should be regarded as traces of compound behavior comprising bipedal walking, wearing and production of shoes. Footprints of naked feet offer no restrictions in being classified into the ichnotaxonomical system.
 
The Iberian Basin or its present-day expression, the Iberian Ranges, was refilled with red bed sediments of alluvial origin during the late Olenekian–Anisian period represented by the Cañizar (Olenekian–Anisian) and Eslida (Anisian) Formations, both commonly known as Buntsandstein facies. In the late part of the Anisian, the Tethys Sea reached the eastern side of the Iberian microplate, represented by the shallow marine facies of the Landete and Cañete Formations, also called Muschelkalk facies. The ichnites studied in this paper belong to the Anisian continental-marine transition in the SE Iberian Ranges. The Cañizar Formation shows the oldest Triassic footprints found in the Iberian Peninsula, consisting in swimming, uncomplete lacertoid three digit Rhynchosauroides traces with possibly resting (cubichnia) and furrowing (pascichnia) Cruziana/Rusophycus due to large triopsids. Specimens from Lacertoïd and Crocodiloïd groups have been collected in the Eslida Formation. Rhynchosauroides sp. is the most representative ichnospecies of the first group, while in the Crocodiloïd group, the presence of Chirotherium barthii Kaup 1835 and Isochirotherium cf coureli (Demathieu 1970) are distinctive. In the Landete Formation specimens are found from Crocodiloïd and Dinosauroïd groups. Brachychirotherium gallicum Willruth 1917, Brachychirotherium sp. and Chirotherium sp. are characteristic of the first one, and ‘Coelurosaurichnus' perriauxi and cf Paratrisauropus latus as the most representative of the second group. Some of the specimens described here present ancestors in the Early Triassic and have been described in the Triassic of North America, Italy and France. Possible paleogeographical connections with faunas of SE France can be inferred. Based on different sedimentary structures and plant remains, the footprints are related to fluvial systems within huge flood plains, playa and shallow marine environments, with alternating dry and wet periods. The vertical ichnites distribution during the Anisian shows that the fauna modification was weak at a high clade level. In the Triassic of the Iberian microplate, there are no findings of traces prior to the Anisian, and the footprint content for the Middle Triassic is less diversified than in other neighbouring regions. By comparison with other western Pangea areas, there was a later appearance of the forms after the end-Permian mass extinction event in the studied area.
 
In 1BO, one of the outcrops of Bin el Ouidane sites, there are theropod footprints with narrow toemarks that are small in size. The prints, even those from the same trackway, are formed in two superposed levels (from an earlier and later time) of finely laminated sandstones separated by some three centimeters of sediment. The upper level cannot be identified as the tracking surface, given that the structures that accompany the footprints are similar to those of the lower level, which are clearly undertracks. The characteristics of many of them (very narrow toemarks, high divarication, very elongated marks of toe III, width of the footprints and very narrow trackways) are typical of avian ichnites. In this work, such an attribution has been ruled out and it is postulated that the trackmaker is a small theropod dinosaur, from the description and origin of the print structures.
 
The Western Australian soldier crab, Mictyris occidentalis Unno 2008, presents an unusual association between crab and ichnological features. As the crab progresses through life, its behavior becomes more complex and its ichnological products more varied: from small, sandy clots and pustules, progressing to various types of shallow, pellet-roofed feeding tunnels and then, when emergent and swarming, eruption structures (exit holes), discard feeding pellets, and re-entry rosettes. The size of tunnels, exit holes, pellets, and re-entry rosettes are commensurate with the size of the crabs. The link between crab ichnological product, life stage, and behavior is so direct that its ichnological features can be used as a surrogate to reconstruct population age structure and age-related behavior. In effect, as it progresses through life from being wholly infaunal to alternating infaunal and epifaunal with swarming behavior, autoecologically and palaeoecologically, the ichnology of the Western Australian soldier crab is a “Rosetta Stone” (used metaphorically, for a series of inscriptions on the tidal flat surface) that can be interpreted to determine species occurrence and population age structure, unravel age-related behavior, and, if preserved as ichnofossils, interpret fossil crab sizes, population structures, behavior and palaeoenvironment.
 
The concept of dynamic similarity between mechanical properties of vertebrates and engineered structures has served in previous work to suggest that there is a power law relationship between vertebrate speeds and stride length. This relationship, with some additional assumptions about hind limb height, has permitted the calculation of speeds from fossil trackways of dinosaurs. However, there are claims that uncertainties are large. In this work we analyze the accuracy of speed calculations for fossil vertebrates based on fossil trackways by using data derived from both athletic competitions and an experiment with humans walking and running on a beach. Our results show that although there are somewhat different running regimes, in general terms human speed can be described in a simple way, and differences between observed and predicted speeds usually are no more than 10–15%. Thus, while recognizing that some uncertainty remains in the estimation of hind limb height, we conclude that reliable speed calculations can be obtained from vertebrate fossil trackways. Our results also show that very reliable speed estimates can be obtained from human fossil trackways directly from stride length measurements.
 
Glossoscolex bergi (Glossoscolecidae) is a giant earthworm from the rainforest of Misiones (Argentina). The large size of its aestivation chamber and the meniscate burrows connected to it allow us to describe morphological details and reinterpret some characteristics of the fossil counterpart Castrichnus incolumis. The concavity of menisci, either in the burrow or in those pellets lining the chamber, shows concentric ridges and radiating striae that result from the impression of the last segments of the body. The meniscate burrows associated to the chamber are different from described ichnospecies of Taenidium, because of the surface texture of the meniscus. The aestivation chamber was produced during an atypical four-month drought in a region that lacks a seasonal climate. This suggests that Castrichnus incolumis would be also an indicator of drought periods even in non seasonal climates.
 
Top-cited authors
George Poinar
  • Oregon State University
A. Hallam
  • University of Birmingham
Paul B Wignall
  • University of Leeds
Anthony R. Fiorillo
  • New Mexico Museum of Natural History and Science
Cajus G. Diedrich
  • Europaschule Obermayr