Article

Dinosaur burrows in the Otway Group (Albian) of Victoria, Australia, and their relation to Cretaceous polar environments

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Abstract

Three enigmatic structures in an outcrop of the Otway Group (Albian) of Victoria, Australia, compose the first known evidence suggestive of dinosaur burrows outside of North America and the oldest from the fossil record. The most complete of the Otway structures nearly matches the size and morphology of a burrow attributed to the only known burrowing dinosaur, Oryctodromeus cubicularis from the Upper Cretaceous (Cenomanian) of Montana (USA). The suspected burrows cross-cut alluvial facies and overlie nearby strata containing dinosaur tracks. The structures contain identical sand fills in their upper portions, implying a near-synchronous origin and filling; graded bedding in the most complete structure also indicates passive filling of an originally open structure. This probable burrow is a 2.1m long, gently descending, semi-helical tunnel, with a near-constant diameter (about 30cm) that connects with an enlarged terminal chamber. The structures are unlikely to have been caused by physical or chemical sedimentary processes, and hence are considered as biogenic structures; moreover, their size and morphology imply tetrapod tracemakers. Burrow allometry indicates tracemakers with a mass of 10–20kg, matching size estimates for small ornithopods from the Otway Group. Burrowing behavior in hypsilophodontid-grade dinosaurs, which compose most of the dinosaurian assemblage in the Lower Cretaceous of Victoria, was proposed previously as an adaptation for surviving formerly polar conditions in southeastern Australia. This paradigm is explored in detail, particularly through actualistic examples of tetrapod burrowing in cold climates. These structures may provide the first clues of ornithopod burrowing in these extreme environments, while also establishing search images for similar structures in other Lower Cretaceous outcrops in Victoria.

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... Recent advances in vertebrate paleontology suggest that fossorial behavior in tetrapods evolved long before the Cenozoic in a variety of groups, including temnospondyls , lysorophids (Hasiotis et al., 1993;Hembree et al., 2004Hembree et al., , 2005, therapsids (Smith, 1987;Groenewald et al., 2001;Damiani et al., 2003;Lucas et al., 2006;Colombi et al., 2008;Tanner and Lucas, 2008;Modesto and Botha-Brink, 2010;Bordy et al., 2011;Riese et al., 2011), mammals (Hasiotis, 2004;Hasiotis et al., 2004;Luo and Wible, 2005;Simpson et al., 2010;Riese et al., 2011), procolophonids (Stanistreet and Turner, 1979;Groenewald, 1991;deBraga, 2003;Sidor et al., 2008), and dinosaurs (Varrichio et al., 2007;Martin, 2009;Huh et al., 2010). Related burrow architecture ranges from simple tubes (Hembree et al., 2004(Hembree et al., , 2005 and gently dipping, distally enlarged tunnels (Loope, 2006;Varrichio et al., 2007;Martin, 2009;Modesto and Botha-Brink, 2010;Storm et al., 2010;Bordy et al., 2011), to helical, single-chamber structures (Smith, 1987;Miller et al., 2001) and networks of multiple branched tunnels and chambers (Groenewald et al., 2001;Hasiotis et al., 2004;Lucas et al., 2006;Colombi et al., 2008;Riese et al., 2011). ...
... Recent advances in vertebrate paleontology suggest that fossorial behavior in tetrapods evolved long before the Cenozoic in a variety of groups, including temnospondyls , lysorophids (Hasiotis et al., 1993;Hembree et al., 2004Hembree et al., , 2005, therapsids (Smith, 1987;Groenewald et al., 2001;Damiani et al., 2003;Lucas et al., 2006;Colombi et al., 2008;Tanner and Lucas, 2008;Modesto and Botha-Brink, 2010;Bordy et al., 2011;Riese et al., 2011), mammals (Hasiotis, 2004;Hasiotis et al., 2004;Luo and Wible, 2005;Simpson et al., 2010;Riese et al., 2011), procolophonids (Stanistreet and Turner, 1979;Groenewald, 1991;deBraga, 2003;Sidor et al., 2008), and dinosaurs (Varrichio et al., 2007;Martin, 2009;Huh et al., 2010). Related burrow architecture ranges from simple tubes (Hembree et al., 2004(Hembree et al., , 2005 and gently dipping, distally enlarged tunnels (Loope, 2006;Varrichio et al., 2007;Martin, 2009;Modesto and Botha-Brink, 2010;Storm et al., 2010;Bordy et al., 2011), to helical, single-chamber structures (Smith, 1987;Miller et al., 2001) and networks of multiple branched tunnels and chambers (Groenewald et al., 2001;Hasiotis et al., 2004;Lucas et al., 2006;Colombi et al., 2008;Riese et al., 2011). Complex tetrapod burrow systems that indicate communal behavior by the producers are poorly known from pre-Cenozoic strata including only six published occurrences: (1) The earliest evidence of colonial dwellings comes from the Upper Triassic Driekoppen Formation of the Karoo Basin, South Africa and is attributed to therapsids (Groenewald et al., 2001); (2-4) similar complex burrows equally referred to advanced synapsids are reported from the Late Triassic Chinle Formation of southeastern Utah, United States , the Late Triassic Ischigualasto Formation of northwestern Argentina (Colombi et al., 2008), and the Lower Jurassic Navajo Sandstone of east-central Utah, United States (Lucas et al., 2006;Riese et al., 2011); (5) large-diameter burrow networks possibly constructed by fossorial mammals are recorded from the Upper Jurassic Morrison Formation of southern Utah, United States (Hasiotis, 2004;Hasiotis et al., 2004); (6) finally, mammalian den complexes probably excavated and used by multiple individuals were mentioned from the Upper Cretaceous Wahweap Formation of southern Utah, United States . ...
... Considering the complex architecture, large diameter, gently inclined entrances, sinuous tunnels, enlarged terminal chambers, and distinct transverse grooves, scratch-digging tetrapods are the most likely excavators of the described burrows (Groenewald et al., 2001;Miller et al., 2001;Hasiotis et al., 2004Hasiotis et al., , 2007Loope, 2006;Martin, 2009;Riese et al., 2011). Even though skeletal remains are not associated with these structures, careful comparative analyses of the burrow architecture, surficial morphology, and sedimentological context may be helpful to narrow the search for potential tracemakers and to interpret their behavior. ...
... The criteria that are not met are commonly associated with more complex social behavior, including multiple chambers, variable branching pattern, and more complex underground mazes (Lucas et al., 2006b). The overall geometry and measured width-to-height ratios of the terminal chamber are consistent with those of some tetrapod burrows reported from the fossil record (Fig. 3C;Damiani et al., 2003;Lucas et al., 2006b;Martin, 2009;Smith, 1987;Varricchio et al., 2007). Downward tilting tunnels are a common characteristic of subterranean vertebrate burrows (Fig. 3C;Damiani et al., 2003;Hasiotis et al., 2004Hasiotis et al., , 2007), and chambers are commonplace and occur at the terminus of a shaft (Hasiotis et al., 2007). ...
... Downward tilting tunnels are a common characteristic of subterranean vertebrate burrows (Fig. 3C;Damiani et al., 2003;Hasiotis et al., 2004Hasiotis et al., , 2007), and chambers are commonplace and occur at the terminus of a shaft (Hasiotis et al., 2007). The Mauch Chunk structure is filled with two normally graded beds that are consistent with other reported fills from Cretaceous dinosaur burrows (Martin, 2009;Varricchio et al., 2007). Two generations of normally graded fill were identified from Cretaceous dinosaur burrows in Montana that aided in the preservation of the dinosaurian ornithopod Oryctodromeus cubicularis (Varricchio et al., 2007). ...
... Two generations of normally graded fill were identified from Cretaceous dinosaur burrows in Montana that aided in the preservation of the dinosaurian ornithopod Oryctodromeus cubicularis (Varricchio et al., 2007). In the Australian Cretaceous, a probable dinosaur burrow occurs as isolated fills with sediment that does not match any of the surrounding lithologies (Martin, 2009). Accordingly, these graded beds are attributed to passive filling of the original open structure (Martin, 2009). ...
Article
A burrow of probable amphibian origin was discovered in the upper member of the Mississippian Mauch Chunk Formation in eastern Pennsylvania. Facies analysis of the upper member indicates that deposition occurred in an ephemeral–braided stream setting. The burrow is housed in a mudstone and is filled by two graded beds of conglomerate to sandstone. It is characterized by a flared opening leading into a narrower slightly helical tunnel that ends in an inflated ovate chamber approximately 51 to 60 cm in diameter with a maximum height of 20 cm. The flared opening is stratigraphically higher than the elevation at the base of the chamber. The tunnel has a semicircular base.The geometries, abrupt angle changes, inflated termination, width-to-height ratios of the terminal chamber, and graded fill indicate that the structure was an open void prior to sedimentation. The geometry and size of this structure are incompatible with known invertebrate burrows and erosional features. Palaeosauropus primaevus, an amphibian footprint ichnotaxon, recovered from the Mauch Chunk Formation, was made by an amphibian of sufficient size to create such a large burrow. This type of burrowing was most likely a response to seasonal droughts as local water sources evaporated.
... Mammals are among the main presentday fossorial vertebrates, constructing complex burrows with several tunnels, branches, entrances, and chambers (Kinlaw, 1999). However, the fossil record is plenty of other examples of fossorial lineages: Paleozoic fishes and tetrapods (Hembree et al., 2004;Francischini et al., 2018); Permian-Triassic reptiles and synapsids (Modesto & Botha-Brink, 2010); Jurassic-Cretaceous ornithopod dinosaurs (Martin, 2009;Krumenacker et al., 2019), synapsids (Dentzien-Dias et al., 2008;Riese et al., 2011), and possibly crocodylomorphs (Martinelli et al., 2019). ...
... A simple and sinuous tunnel with a terminal chamber preserved in Cenomanian deposits in the USA was attributed to the euornithopod Oryctodromeus cubicularis due to skeletal remains preserved within the burrow filling (Varricchio et al., 2007;Fearon & Varricchio, 2016). Similar material was described from the Albian Otway Group of Australia (Martin, 2009). Despite the burrow architecture and the presence of skeletal remains in the burrow filling being comparable with the paleoburrow found in the Adamantina Formation, the morphology, orientation, and diameter of both burrows are not similar. ...
Article
Full-text available
Vertebrates produce a variety of trace fossils, mostly tracks and trackways, coprolites, and burrows resulting from fossorial and subterranean habits. Burrows, particularly, tend to represent temporary or permanent shelter. Vertebrate burrows are relatively understudied in the Brazilian Mesozoic units, as well as in Cretaceous rocks worldwide. This study aims to analyze a paleoburrow in the Upper Cretaceous Adamantina Formation and to discuss its paleobiological and paleoenvironmental implications. A descriptive study was carried out on the paleoburrow morphology, following aspects such as orientation, architecture, and dimensions, and facies association analysis provided the interpretation of the paleoenvironment in which the tracemaker lived. The origin of the paleoburrow was highlighted, as well as the size of its possible producer, besides inferring the exposure time of the paleoburrow from taphonomic interpretations, which contains allochthonous bone remains. The results suggest long periods of dry conditions, as previously suggested for the much-debated Adamantina Formation, interrupted by flooding events as evidenced by facies analysis and suggested by the lungfish burrow. The possibility of a lungfish record also expands the presence of these animals to Adamantina Formation, even though more data are needed to understand the paleoecology of these formation.
... However, simple structures composed of shafts and chambers are common in the geological records and associated with different organisms, such as fishes, reptiles, and crocodylomorphs (Varricchio et al., 2007;Martin, 2009;Marshal and Rogers, 2012;Martinelli et al., 2019;Krumenacker et al., 2019). Simple tunnels with no chambers are difficult to attribute or to infer the producer. ...
... Therefore, we disregard this group as possible trace makers. We also disregard dinosaurs due to the size and architecture of the burrows (e.g., Martin, 2009 (Whitaker et al., 2007). Regarding the architectural morphology, the absence of a terminal chamber suggests that the tracemaker did not present a slender and elongated body, which would have required some enlargement at the bottom of the burrow for its free movement and rotation in the change orientation, as occurs in lizards and crocodiles. ...
Article
Burrowing behavior is an important adaptation of animals that live in arid and semi-arid conditions. In this paper, we describe examples of vertebrate burrows from the Upper Cretaceous (Maastrichtian) Adamantina Formation of the Bauru Basin, Brazil, most likely produced by turtles. The Adamantina Formation preserves abundant and diverse turtle body fossils such as Bauruemys elegans (Testudines: Pleurodira); however turtle burrows have not been previously documented. The newly reported burrows are preserved in fluvial sandstone facies and exposed in sections that partially preserve their three-dimensional geometry. Burrows are simple J-shaped tunnels with a cross-sectional shape that is semicircular (half-dome) with a flattened floor. Such burrows show a partially preserved entrance with an inclined ramp angle (22°), and grooves and ridges up to 1 cm in width preserved along the burrows walls and floor. The architecture and sedimentary facies of the host sandstone body, together with the occurrence of Taenidium barretti and the absence of rhizoliths, suggest that the burrow was excavated by scratch digging into an exposed point bar of a meandering river channel. Based on burrow morphology, dimensions, as well as ridges,and grooves in the walls and floor, we propose that burrows were formed by a chelonian (such as a freshwater turtle) during aestivation. We highlight that these are first examples of turtle burrows reported from the Cretaceous, and their occurrence reinforces the hypothesis that the original function of turtle shells was as an adaptation to fossorial behavior.
... This was interpreted as a burrow used for parental care and the first evidence of burrowing behaviour for a nonavian dinosaur. A second record is reported from the Albian Otway Group of Victoria, Australia (Martin, 2009). It includes several burrows of up to two meter-long semi-helical tunnel ending in an enlarged terminal chamber. ...
... It includes several burrows of up to two meter-long semi-helical tunnel ending in an enlarged terminal chamber. They were supposedly dug by hypsilophodontid-grade dinosaurs as response to extreme polar conditions during the Lower Cretaceous in southeastern Australia (Martin, 2009). In addition, Martin (2001; see also Martin and Varricchio, 2011) briefly mentioned burrows made probably by mammals in the Campanian Two Medicine Formation of Choteau, Montana, USA. ...
... The morphology of this structure is similar to the previously described burrows of Oryctodromeus and other possible neornithischian burrows (Varricchio et al., 2007a;Martin, 2009). The cross-sectional width and height of this trace is like that of the previously described burrow from the Vaughn Member (Varricchio et al., 2007a), which had a diameter of about 30 cm. ...
... The cross-sectional width and height of this trace is like that of the previously described burrow from the Vaughn Member (Varricchio et al., 2007a), which had a diameter of about 30 cm. The sinuous form of the ichnofossil is also similar in morphology to the burrows described by Varricchio et al. (2007A) and Martin (2009). ...
... This was interpreted as a burrow used for parental care and the first evidence of burrowing behaviour for a non-avian dinosaur. A second record is reported from the Albian Otway Group of Victoria, Australia (Martin, 2009). It includes several burrows of up to two meter-long semi-helical tunnel ending in an enlarged terminal chamber. ...
... It includes several burrows of up to two meter-long semi-helical tunnel ending in an enlarged terminal chamber. They were supposedly dug by hypsilophodontid-grade dinosaurs as response to extreme polar conditions during the Lower Cretaceous in southeastern Australia (Martin, 2009). In addition, Martin (2001; see also Martin and Varricchio, 2011) briefly mentioned burrows made probably by mammals in the Campanian Two Medicine Formation of Choteau, Montana, USA. ...
... [4,6,8,70,71]). Although initially developed to combat seasonal temperature fluctuations and water stress associated with seasonally dry climate regimes at low to mid-latitudes, burrowing behavior may have also allowed organisms to live at high latitudes by circumventing seasonal temperature fluctuations and perhaps serving as a refuge during winter dormancy [5][6][7]72,73]. ...
... Many different morphological characteristics have been utilized to identify potential architects of continental burrows including overall burrow architecture, superficial markings, dimensions, spatial relationships, and resemblance to known tetrapod burrows [4,5,71,73]. The architectural and superficial morphologies described for Morphotypes 1 and 2 above indicate that the burrows were likely constructed by tetrapods. ...
... One of us (Martin) has also identified additional invertebrate burrows at several localities in the Otway Group. Martin (2009b) also reported possible dinosaur burrows in Otway Group rocks of Knowledge Creek, the only dinosaur trace fossil other than tracks noted from the Early Cretaceous in this part of Australia. The majority of dinosaur body fossils recovered from the Otway Group were derived from one locality, Dinosaur Cove (Rich & Vickers-Rich 2000). ...
... Directionality of dinosaur movement indicated by track assemblages on both blocks may have been influenced by the local landscape; nevertheless, this can not be supported categorically without more evidence. Thus, the results of our study contribute further to continuing discussions of polar dinosaurs and their adaptations to wintertime conditions, whether through hibernation (Rich et al. 1988, Chinsamy et al. 1998, Martin 2009b, migration (Parrish et al. 1987, Currie 1989 or year-round activity (Rich et al. 1988, Fiorillo & Gangloff 2001, Bell & Snively 2008, Fanti & Miyashita 2009). This discovery also bodes well for finding more tracks at Milanesia Beach and in similar floodplain facies of the Otway Group, eventually leading to a clearer understanding of dinosaur presence and behaviours in these formerly polar environments of Australia. ...
Article
Full-text available
The Eumeralla Formation (Aptian-Albian) of the Otway Group in Victoria, Australia, has yielded a significant amount of dinosaur skeletal material since the late 1970s, which, when combined with finds from the Wonthaggi Formation (Aptian) of the upper Strzelecki Group, constitute the best-documented polar-dinosaur assemblage in the Southern Hemisphere. In contrast, dinosaur tracks have barely augmented this body fossil record; up to now, only one ornithopod track had been documented in any detail from the Otway Group. In this study, we report a new find of at least 24 dinosaur tracks preserved on two ripple-bedded sandstone blocks of the Eumeralla Formation, discovered at Milanesia Beach, Victoria. This dinosaur-track assemblage is the best in terms of numbers and quality found thus far in formerly polar environments of the Southern Hemisphere. One block includes the first known dinosaur trackway from the Cretaceous of Victoria, consisting of three consecutive footprints made by a small theropod. The assemblage indicates three differently sized theropods, thus providing new insights on dinosaur diversity and activity not indicated previously by body fossils in the Eumeralla Formation. Tracks are preserved in fluvial floodplain deposits and were possibly imprinted on emergent floodplain surfaces following seasonal flooding during a polar summer. The abundant tracks at this site suggest more such finds are likely in floodplain deposits of the Otway Group, although behavioural and preservational conditions unique to polar environments may have limited their formation.
... Many different morphological characteristics have been utilized to identify potential architects of continental burrows including overall burrow architecture, superficial markings, dimensions, spatial relationships, and resemblance to known tetrapod burrows [4], [5], [71], [73]. The architectural and superficial morphologies described for Morphotypes 1 and 2 above indicate that the burrows were likely constructed by tetrapods. ...
... [4], [6], [8], [70], [71]). Although initially developed to combat seasonal temperature fluctuations and water stress associated with seasonally dry climate regimes at low to mid-latitudes, burrowing behavior may have also allowed organisms to live at high latitudes by circumventing seasonal temperature fluctuations and perhaps serving as a refuge during winter dormancy [5]–[7], [72], [73]. ...
Article
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Large-diameter ichnofossils comprising three morphotypes have been identified in the Upper Triassic Ischigualasto and Los Colorados formations of northwestern Argentina. These burrows add to the global record of the early appearance of fossorial behavior during early Mesozoic time. Morphotypes 1 and 2 are characterized by a network of tunnels and shafts that can be assigned to tetrapod burrows given similarities with previously described forms. However, differences in diameter, overall morphology, and stratigraphic occurrence allow their independent classification. Morphotype 3 forms a complex network of straight branches that intersect at oblique angles. Their calcareous composition and surface morphology indicate these structures have a composite biogenic origin likely developed due to combined plant/animal interactions. The association of Morphotypes 1 and 2 with fluvial overbank lithologies deposited under an extremely seasonal arid climate confirms interpretations that the early appearance of burrowing behavior was employed by vertebrates in response to both temperature and moisture-stress associated with seasonally or perpetually dry Pangean paleoclimates. Comparisons of burrow morphology and biomechanical attributes of the abundant paleovertebrate fauna preserved in both formations permit interpretations regarding the possible burrow architects for Morphotypes 1 and 2. In the case of the Morphotype 1, the burrow constructor could be one of the small carnivorous cynodonts, Ecteninion or Probelesodon. Assigning an architect for Morphotype 2 is more problematic due to mismatches between the observed burrow morphology and the size of the known Los Colorados vertebrates.
... Another type of trace fossil is indicated by the vertically oriented eggs of T. formosus clutches, which suggest postlaying arrangement, presumably by one of the parents (Horner 1984(Horner , 1987Varricchio et al. 1997). Most recently, dinosaur burrows interpreted from the Upper Cretaceous Blackleaf Formation of Montana (Varricchio et al. 2007) and the Lower Cretaceous Otway Group of Australia (Martin 2009) may have served in the protection of young. In short, dinosaur trace fossils have supplied important scientific information about dinosaur nest sites augmenting data derived from body fossils, sedimentology, geochemistry or other sources of geological data. ...
... The ichnology of dinosaur nest sites has been a topic covered by a few researchers, but with an emphasis on traces of the dinosaurs themselves, and with less attention paid to additional tracemakers associated with these nests. Dinosaur trace fossils associated with dinosaur nest sites, as mentioned previously, include nest structures (sedimentary rims) and positioning of eggs after egg-laying (Varricchio et al. 1997;Chiappe et al. 2004), and potentially burrows (Meng et al. 2004;Varricchio et al. 2007;Martin 2009). Additional traces might include tracks, trampling of eggshell material in the nest, eggemergence (hatching window) fractures in eggshells (Cousin et al. 1994;Mueller-Towe et al. 2002), gastroliths, coprolites, regurgitants and tooth marks in vertebrate remains within the nest. ...
Article
Full-text available
Insect trace fossils, such as burrows, pupation chambers and nests, can provide broad paleoecological insights by helping to define paleohydrology, effects of seasonality or conditions of associated paleosols. Insect traces adjacent to nesting sites of the dinosaur Troodon formosus in the Cretaceous (Campanian) Two Medicine Formation near Choteau, Montana, demonstrate such paleoecological utility. One outcrop in particular contains an abundance of insect burrows and pupation chambers in a calcareous paleosol. Most trace fossils are interpreted as apocritan (wasps and bees) burrows, brooding chambers and cocoons. Apocritans prefer to construct burrows and brooding chambers in well-drained soils during relatively dry conditions (avoiding wet seasons). Their trace fossils are consistent with previous inferences of semi-arid conditions and seasonality for the Two Medicine Formation. Moreover, apocritan nesting is likely to have occurred in the same places and conditions as dinosaur nests: well above the local water table and during dry seasons. Such trace fossils hold the potential for more precise definitions of paleoecological factors in dinosaur nest sites. For example, within the Two Medicine Formation, the Celliforma ichnofacies is commonly associated with eggs of T. formosus and Continuoolithus, but not with those of Maiasaura peeblesorum, perhaps indicative of subtle nesting site preferences.
... Within these deposits, the Eumeralla Formation (Aptian-Albian) of the Otway Group is recognised as producing the richest dinosaur body fossil and ichnological assemblages with no fewer than eight documented dinosaur (body and/or trace) fossil localities (Poropat et al. 2018). These include body fossil sites such as Eric the Red West (Duncan et al. 2021), Point Franklin (Poropat et al. 2018), Point Lewis (Poropat et al. 2018), and Marengo (Poropat et al. 2018), and trace fossil sites such as Milanesia Beach (Martin et al. 2012), Knowledge Creek (Martin 2009(Martin , 2016, and Browns Creek (see Martin 2016: Appendix II recommendation to keep the nickname 'Skenes Creek tracks'). Dinosaur Cove is known for both body and trace fossils (Benson et al. 2012;Martin et al. 2014). ...
Article
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Dinosaur fossils of the Lower Cretaceous (Aptian–Albian) Eumeralla Formation (Otway Basin) of Victoria provide insights into the faunal and ichnofaunal diversity of southern hemisphere high latitude dinosaurs during the initial separation of Australia from Antarctica. To date, at least eight dinosaur fossil locations have been reported from this formation. In this paper, we describe a new tracksite locality along the coastline of Wattle Hill that represents the most westerly occurrence of dinosaur fossils in the state. Some of the Wattle Hill prints resemble tracks attributed to ornithopodan trackmakers from neighbouring tracksites of the Eumeralla Formation (Knowledge Creek, Browns Creek), while others resemble bird prints. The site also preserves a large non-avian theropod footprint that resembles Megalosauropus prints from the Lower Cretaceous (Valanginian–Barremian) Broome Sandstone, Western Australia that if correct, extends the temporospatial range of this ichnogenus. The Wattle Hill tracks vary in their erosion between and within tracksites, from a natural mould (concave epirelief), transmitted tracks, possibly penetrative tracks and infilled reliefs that resemble (but differ from) natural casts. With the constant weathering of the Eumeralla Formation exposures, it seems likely that additional dinosaur tracks fossils will be discovered with continued Victorian coastal explorations.
... However, no specimens were formally published until Rich and Rich (1988) briefly described the partial skull roof NMV P185990. In addition to body fossils (on which more below), isolated footprints and possible burrows, similar to those attributed to Oryctodromeus cubicularis (Varricchio et al., 2007), have been recorded from Victoria (Martin, 2009(Martin, , 2016. Finally, and perhaps most interestingly, the larger-bodied ornithopods of New South Wales and Queensland are conspicuous by their absence in Victoria. ...
Article
Ornithopod dinosaurs are relatively common in the Cretaceous of Australia, particularly in the state of Victoria, which has yielded five taxa to date: two from the upper Strzelecki Group (upper Barremian–lower Aptian), and three from the Eumeralla Formation (upper Aptian–upper Albian). Whereas four of these are based solely on cranial material, Diluvicursor pickeringi is represented by a partial postcranium and is the only ornithopod specimen heretofore reported from the Eric the Red West (ETRW) site. Herein, we describe nine ornithopod dentulous elements from the Eumeralla Formation: seven from ETRW, and two from nearby sites. The four ETRW maxillae are divided into three morphotypes that are morphologically compatible with Leaellynasaura amicagraphica, Atlascopcosaurus loadsi, and cf. Galleonosaurus dorisae, respectively. Although this implies that Diluvicursor might not represent a distinct taxon, this is circumstantial. The new Leaellynasaura maxillae are evidently adult exemplars, contrasting with the juvenile holotype, whereas the sole Atlascopcosaurus maxilla is more complete than all previously referred specimens; consequently, revised diagnoses of both taxa are presented. Finally, the presence in the Eumeralla Formation of cf. Galleonosaurus—otherwise known only from the upper Strzelecki Group—implies that this taxon persisted from the Barremian to the Albian, and potentially indicates remarkable environmental stability in southeast Australia during the late Early Cretaceous.
... 53 Putative dinosaur burrows from high-latitude deposits of the Otway Group in Victoria, Australia, have also been described as a possible adaptation to survival in polar conditions. 54 In extant birds, feathers of various forms show diverse functionality depending on the taxon (e.g., flight, camouflage, display, insect traps, shedding parasite loads), but almost invariably possess types that serve some role in insulation. 55 Although feather preservation is currently unknown in the PCF, it has recently been found in other formations that preserve representatives of each of the theropod groups identified in the PCF, namely Ornithomimisauria, 56 Deinonychosauria, 57,58 and even Tyrannosauroidea 59 (most notably the large, downy-covered tyrannosauroidean Yutyrannus huali from the cool, temperate Yixian Formation of China 60 ). ...
Article
The unexpected discovery of non-avian dinosaurs from Arctic and Antarctic settings has generated considerable debate about whether they had the capacity to reproduce at high latitudes—especially the larger-bodied, hypothetically migratory taxa. Evidence for dinosaurian polar reproduction remains very rare, particularly for species that lived at the highest paleolatitudes (>75°). Here we report the discovery of perinatal and very young dinosaurs from the highest known paleolatitude for the clade—the Cretaceous Prince Creek Formation (PCF) of northern Alaska. These data demonstrate Arctic reproduction in a diverse assemblage of large- and small-bodied ornithischian and theropod species. In terms of overall diversity, 70% of the known dinosaurian families, as well as avialans (birds), in the PCF are represented by perinatal individuals, the highest percentage for any North American Cretaceous formation. These findings, coupled with prolonged incubation periods, small neonate sizes, and short reproductive windows suggest most, if not all, PCF dinosaurs were nonmigratory year-round Arctic residents. Notably, we reconstruct an annual chronology of reproductive events for the ornithischian dinosaurs using refined paleoenvironmental/plant phenology data and new insights into dinosaur incubation periods. Seasonal resource limitations due to extended periods of winter darkness and freezing temperatures placed severe constraints on dinosaurian reproduction, development, and maintenance, suggesting these taxa showed polar-specific life history strategies, including endothermy.
... Other behaviors such as burrowing or hibernation were excluded in our study as they are unlikely means of temperature regulation for adult Coelophysis and Plateosaurus. However, several smaller dinosaurs from temperate latitudes later in the Mesozoic are known or suspected burrowers [127,128]. It is not outside the realm of possibility that juvenile Plateosaurus (or other small prosauropods such as the 15 kg Thecodontosaurus) would have leveraged the benefits of burrowing. ...
Article
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We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate the metabolic function of the Late Triassic dinosaurs Plateosaurus and Coelophysis during global greenhouse conditions. We tested a variety of assumptions about resting metabolic rate, each evaluated within six microclimate models that bound paleoenvironmental conditions at 12° N paleolatitude, as determined by sedimentological and isotopic proxies for climate within the Chinle Formation of the southwestern United States. Sensitivity testing of metabolic variables and simulated “metabolic chamber” analyses support elevated “ratite-like” metabolic rates and intermediate “monotreme-like” core temperature ranges in these species of early saurischian dinosaur. Our results suggest small theropods may have needed partial to full epidermal insulation in temperate environments, while fully grown prosauropods would have likely been heat stressed in open, hot environments and should have been restricted to cooler microclimates such as dense forests or higher latitudes and elevations. This is in agreement with the Late Triassic fossil record and may have contributed to the latitudinal gap in the Triassic prosauropod record.
... CC-BY 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. [129,130]. Fossorial behavior allows for the exploitation of more stable microhabitats in environments with higher variance in daily or annual air temperature. ...
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We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate the metabolic function of Late Triassic dinosaurs Plateosaurus and Coelophysis during global greenhouse conditions. We tested them under a variety of assumptions about resting metabolic rate, evaluated within six microclimate models that bound paleoenvironmental conditions at 12° N paleolatitude, as determined by sedimentological and isotopic proxies for climate within the Chinle Formation of the southwestern United States. Sensitivity testing of metabolic variables and simulated “metabolic chamber” analyses support elevated “ratite-like” metabolic rates and intermediate “monotreme-like” core temperature ranges in these species of early saurischian dinosaur. Our results suggest small theropods may have needed partial to full epidermal insulation in temperate environments, while fully grown prosauropods would have likely been heat stressed in open, hot environments and should have been restricted to cooler microclimates such as dense forests (under any vegetative cover) or those seen at higher latitudes and elevations. This is in agreement with the Late Triassic fossil record and may have contributed to the latitudinal gap in the Triassic prosauropod record.
... Additionally, the robust forelimbs found in the close relatives of Oryctodromeus, may indicate burrowing habits across the orodromine clade (Huh et al. 2010). In contrast to these taphonomic and anatomical arguments, possible burrow traces lacking bones from the Cretaceous Otway Group of Australia were considered to represent those of small ornithopods (Martin 2009). Full documentation of the threedimensional aspects of the exceptional type burrow for Oryctodromeus may thus prove useful in the early field identification of additional burrow traces in the future. ...
Article
Oryctodromeus cubicularis is a small-bodied ornithischian dinosaur from the mid-Cretaceous Blackleaf and Wayan Formations of Montana and Idaho, respectively, and is the only documented dinosaur with evidence of a burrowing ecology. The type locality, from the Blackleaf Formation of southwestern Montana, consisted of an infilled burrow structure containing the disarticulated skeletons of one adult and two juveniles and represents a rare association of body fossils and trace fossils of a single dinosaur taxon. While these fossils and their paleobiological implications were unprecedented, collection nevertheless necessitated removal of the burrow structure from its geological context and its destruction during body fossil preparation. Here we present the first photogrammetric models of the type locality burrow in its original geological context and three dimensional morphology, constructed from photos taken at three stages in excavation. Because the terminal extent of the burrow was collected prior to the burrow’s complete exposure, the structure was never documented in its entirety. A composite model provides the only holistic documentation of the entire burrow morphology as originally preserved. These models supplement the original burrow description, serve as comparative tools for identifying and diagnosing future discoveries, and demonstrate the utility of pre-existing photographs for later photogrammetric reconstruction.
... Intriguingly, the existence of possible dinosaur burrows has also been reported from the Victorian Early Cretaceous. Martin (2009) noted distinct similarities between sedimentary structures at Knowledge Creek and fossilized burrows from Montana ascribed to the small ornithopod Oryctodromeus cubicularis Varricchio et al. 2007. Consequently, Martin (2009 suggested that the Knowledge Creek structures were also burrows. ...
Article
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Although Cretaceous fossils (coal excluded) from Victoria, Australia, were first reported in the 1850s, it was not until the 1950s that detailed studies of these fossils were undertaken. Numerous fossil localities have been identified in Victoria since the 1960s, including the Koonwarra Fossil Bed (Strzelecki Group) near Leongatha, the Dinosaur Cove and Eric the Red West sites (Otway Group) at Cape Otway, and the Flat Rocks site (Strzelecki Group) near Cape Paterson. Systematic exploration over the past five decades has resulted in the collection of thousands of fossils representing various plants, invertebrates and vertebrates. Some of the best-preserved and most diverse Hauterivian–Barremian floral assemblages in Australia derive from outcrops of the lower Strzelecki Group in the Gippsland Basin. The slightly younger Koonwarra Fossil Bed (Aptian) is a Konservat-Lagerstätte that also preserves abundant plants, including one of the oldest known flowers. In addition, insects, crustaceans (including the only syncaridans known from Australia between the Triassic and the present), arachnids (including Australia’s only known opilione), the stratigraphically youngest xiphosurans from Australia, bryozoans, unionoid molluscs and a rich assemblage of actinopterygian fish are known from the Koonwarra Fossil Bed. The oldest known—and only Mesozoic—fossil feathers from the Australian continent constitute the only evidence for tetrapods at Koonwarra. By contrast, the Barremian–Aptian-aged deposits at the Flat Rocks site, and the Aptian–Albian-aged strata at the Dinosaur Cove and Eric the Red West sites, are all dominated by tetrapod fossils, with actinopterygians and dipnoans relatively rare. Small ornithopod (=basal neornithischian) dinosaurs are numerically common, known from four partial skeletons and a multitude of isolated bones. Aquatic meiolaniform turtles constitute another prominent faunal element, represented by numerous isolated bones and articulated carapaces and plastrons. More than 50 specimens—mostly lower jaws—evince a high diversity of mammals, including monotremes, a multituberculate and several enigmatic ausktribosphenids. Relatively minor components of these fossil assemblages are diverse theropods (including birds), rare ankylosaurs and ceratopsians, pterosaurs, non-marine plesiosaurs and a lepidosaur. In the older strata of the upper Strzelecki Group, temnospondyl amphibians—the youngest known worldwide—are a conspicuous component of the fauna, whereas crocodylomorphs appear to be present only in up-sequence deposits of the Otway Group. Invertebrates are uncommon, although decapod crustaceans and unionoid bivalves have been described. Collectively, the Early Cretaceous biota of Victoria provides insights into a unique Mesozoic high-latitude palaeoenvironment and elucidates both palaeoclimatic and palaeobiogeographic changes throughout more than 25 million years of geological time.
... Possible tetrapod trackways from the Upper Devonian of Victoria were described in 1972 and are amongst the earliest tetrapod trackways known (Warren and Wakefield, 1972). The most comprehensively stud- ied Australian vertebrate trackway sites include Creta- ceous trace fossils from Lark Quarry in Queensland ( Thulborn and Wade, 1979, 1984, 1989Thulborn, 1994;Cook et al., 2010;Hocknull and Cook, 2011;Romilio and Salisbury, 2011;Fletcher et al., 2013Fletcher et al., , 2014Fletcher et al., , 2015Romilio et al., 2013), Broome in Western Australia (Glauert, 1952;Colbert and Merrilees, 1967;Thulborn et al., 1994;Siversson, 2010;McCrea et al., 2011;Thulborn, 2012) and the Otways in Victoria (Martin, 2009;Martin et al., 2012Martin et al., , 2014). Neogene and Quaternary ver- tebrate trace fossils have received comparatively little attention. ...
Article
It is rapidly becoming apparent that the Late Pleistocene vertebrate trace fossil record of southern Australia is much more comprehensive than previously understood, and complements the skeletal fossil record with regard to the distribution of taxa in coastal environments and the palaeobiology of both extinct and extant organisms. We surveyed the majority of prospective Bridgewater Formation outcrops on Kangaroo Island in South Australia and discovered a trace fossil site preserving hundreds of individual traces. A minimum of ten different reptile, bird, and mammal taxa, as well as invertebrates, are represented at the site. Single-grain optically stimulated luminescence dating indicates that the dune in which the traces imprinted was deposited at the beginning of Marine Isotope Stage 5e (135.4 ± 5.9 ka). The traces were made by several extinct taxa including large quadrupeds (most probably diprotodontids), short-faced (sthenurine) kangaroos, and thylacines, as well as extant taxa including possums, the Tasmanian Devil, goannas, shorebirds, and a variety of kangaroos. This site demonstrates that, even though vertebrate trace fossil sites do not often allow the same level of taxonomic differentiation as skeletal fossil deposits, they can nevertheless provide important information about taxon distribution and behavior that can be correlated and contrasted with skeletal fossil assemblages.
... Stratigraphically younger records come, for example, from the Permian (Smith 1987;Liu & Li 2013), Triassic (Miller et al. 2001;Hasiotis et al. 2004;Bordy et al. 2010;Talanda et al. 2011;Voigt et al. 2011), Jurassic and Cretaceous (Loope 2006;Paik et al. 2015). Extant and fossil records of burrowing tetrapods are known from amphibians, therapsids, mammals, parareptiles and eureptiles, including dinosaurs and birds (Smith 1987;Damiani et al. 2003;Varricchio et al. 2007;Martin 2009;Krapovickas et al. 2013). ...
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Here we report a Jurassic tetrapod burrow preserved in association with the partial skeleton of a large sauropod specimen of Omeisaurus jiaoi from Zigong, Sichuan Province, China. The ichnofossil can be divided into two parts, which may indicate two individual trace makers and some social behavior, although the possibility that they are two portions of one trace by a single trace maker cannot be ruled out. The burrow trace was examined via petrographic thin sections and carbonate analysis. Considering the spatial relationship of the burrows and the skeleton, it is likely that decomposition of the sauropod carcass preceded the formation of the burrows. It is possible that the process of decomposition improved the humus level of the soil, which would have attracted more soil-dwelling invertebrates and, by consequence, tetrapod predators thereof. The discovery of ZDM5051 has increased our understanding of global ichnofossil diversity.
... In the fossil record, burrows produced by marine organisms are abundant and are grouped in several ichnofacies, which reflect different behaviors such as feeding and sheltering. In continental settings, such ichnofossils are known to have been produced by Permo-Triassic reptiles (Groenwald, 1991;Modesto and Botha-Brink, 2010), Cretaceous ornithopod dinosaurs (Varricchio et al., 2007;Martin, 2009), and Cenozoic mammals (Martin and Bennett, 1977;Vizca ıno et al., 2001;Hembree and Hasiotis, 2008). ...
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In the last ten years, more than 1,500 large burrows have been discovered in southern and southeastern Brazil, dug in rocks that include weathered granitic and basaltic rocks, sandstones, and other consolidated sediments. Their presence in geological units of Plio-Pleistocene age suggests that large extinct mammals produced these structures. The internal walls exhibit scratches and grooves left by the animals that inhabited these structures. The burrows are straight or slightly sinuous tunnels that measure up to tens of meters in length. One smaller type measures up to 1.5 meter in diameter, and the larger type can reach 2 meters in height and 4 meters in width, suggesting that such structures have been produced by at least two kinds of organisms. This contribution proposes a classification for these ichnofossils under the generic designation Megaichnus igen. nov., consisting of two ichnospecies identified so far: M. major and M. minor ispp. nov. Although the exact identity of the producers of the burrows is yet unknown, the dimensions and morphology point to ground sloths and giant armadillos.
... Large-diameter ichnofossils in the form of tunnels excavated by Cenozoic fossorial vertebrates are, so far and to our knowledge, restricted to South America. Only a few places in other continents host structures of the same kind, but those are much older and much smaller, with maximum lengths and diameters of 6.0 and 0.5 m, respectively (e.g., Popa & Kedzior, 2006;Varrichio et al., 2007;Martin, 2009;Sidor et al., 2009;Modesto & Botha-Brink, 2010;Riese et al., 2011;Talanda et al., 2011). The South American tunnels ("paleocuevas" in Spanish and "paleotocas" in Portuguese) are sometimes called "paleoburrows", but this term is best known as applied to Domichnia-type ichnofossils of invertebrates (worms, mollusks and crustaceans) (e.g., ). ...
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Ichnology, the study of traces, is a fast growing field that feeds from different and diverse disciplinessuch as sedimentology, stratigraphy, biology andpaleontology. The special publication “Ichnology of Latin America - Selected Papers” arose after the Latin American Symposium on Ichnology 2010 (SLIC2010) that was held from October 30th to November7th, 2010, in Sao Leopoldo, south of Brazil. About eighty participants attended the conference, representing 21 institutions from South America, 1 from Central America, 3 from North America, 3 from Europe, and 1 from Asia. The ichnologic community of Latin America is not only one of the largest, but also one of the most active. In that sense, it was worthy to produce this special volume as a synthesis of the current knowledge of ichnology in Latin America. Two papers address the importance of the trace fossils in the terminal Proterozoic-early Phanerozoic successions of South America. Netto (p. 15-26) synthesizes the knowledge of biogenic structures, body fossils and microbially induced sedimentary structures of the terminal Proterozoic basins of southern Brazil, and discusses the possible relationship between these bedsand those from the Avalonian terrane. Buatois & Mángano (p. 27-36) review the ichnology of the Ediacaran-Cambrian Puncoviscana Formation of the North of Argentina from a paleoecologic and macroevolutionary perspective, emphasizing the importance of the feeding strategies related to microbial matgrounds recordedin this succession, as well as the appearance of new body plans and sophisticated feeding strategies. The other contributions explore part of the Phanerozoic ichnologic record in Latin America. Netto et al. (p. 37-68) make a synthetic review of the ichnology of the Paraná Basin in southern Brazil, with emphasis in the invertebrate record. Alonzo-Muruaga et al. (p. 69-81) present the state-of-art of the ichnology of the Upper Paleozoic deposits of Paganzo and Callingasta-Uspallata basins, in the northwestern Argentina. Carmona et al. (p. 83-97) characterize the most representative trace fossils from the Neogene marine deposits of Patagonia (southeastern Argentina), providing an analysis of this ichnofauna considering local paleoceanographic conditions and exploring its relation with the establishment of the Modern Evolutionary Fauna. VillegasMartín & Rojas-Consuegra (p. 99-106) synthesize the knowledge of the Cuban ichnology through the analysis of the existing literature and the material available in collections. These authors also discuss the future perspectives of thisdiscipline in Cuba. Finally, Souto (p. 107-115) over-views the records of vertebrate’s coprolites found indifferent units of Latin America, providing a general evaluation of morphologic aspects necessary todescribe these structures, and introducing the new methods to study them. Some case studies are also presented herein, reflecting the emergent ichnological research in Latin America. Invertebrate and vertebrate bioturbaton as well as bioerosion are the main addressed themes. Souza et al. (p. 119-128) present an initial approach to the ichnology of the Lower Devonian Maecuru Formation (Amazonas Basin, northern Brazil). Dentzien-Dias et al. (p. 129-139) describe vertebrate trace fossils from the Upper Jurassic GuaráFormation (south of Brazil) and the Batoví Memberof the Tacuarembó Formation (north of Uruguay), which contain numerous dinosaur tracks, dominatedby theropod and sauropod tracks and different ver-tebrate burrows. Frank et al. (p. 141-157) synthesizethe present knowledge of large tunnels assigned toCenozoic vertebrates in the southern states of Brazil, and try to identify the possible tracemakers among the South American Megafauna representatives. In the field of bioerosion, Richiano et al. (p. 159-177) focus on the bioerosion structures in Quaternary marine mollusks from the Atlantic Argentine coast (from Rio de la Plata to the south of Santa Cruz province) while Lopes (p. 179-194) describes the bioerosion and bioincrustation in Quaternary body fossilsfrom the Coastal Plain of Rio Grande do Sul State(CPRS), in southern Brazil. There is much more of the ichnology of Latin America than what is presented in this book. Severalhigh quality papers have been published in indexed journals in the last 30 years, and innumerous papers were published in local journals since the 1950s. An important part of this knowledge is missing inthis book, but future editions of the Latin AmericanSymposium on Ichnology will help to fill this gap. To all contributors that helped to construct this compendium, our sincere gratitude. Our special thanks to Jordi M. de Gibert, who was a great enthusiast of the ichnologic research developed in Latin America and who contributed to make this book a reality until hispassing, last September.
... 434All these tunnel-like structures resemble those from Anina in their relatively large 435 dimensions in length and cross-section (although cross-sectional diameter is somewhat 436 smaller in the Anina burrows), simple subcircular cross-section, and sinuous, gently 437 descending trajectory. They are also isolated tunnels that do not form complex networks, 438show swells at the turns of tunnels, and can have a roughly parallel trajectory, as was also 439 reported in the case of the Australian burrows described byMartin (2009). Even the presence 440 of occasional branching was described in the case of Oryctodromeus burrows by Varricchio 441 et al. (2007). ...
Article
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Very large, sparsely distributed, sinuous, gently dipping and occasionally branching tunnels with subordinate swells, as well as possible chambers and scratches, are described from the Hettangian Dealul Budinic Member of the Lower Jurassic continental Steierdorf Formation at Anina in the South Carpathians, Romania, and are interpreted as tetrapod burrows. No bone remains have been found in association with these structures. The morphology and large dimensions of the burrows suggest that the trace-makers were sauropsid amniotes, most probably either crocodyliforms or small-sized basal neomithischian dinosaurs, although their therapsid affinities, despite being less likely, cannot be discarded either. The age, large size and probable origin of these burrows add important information to a poorly documented period of the evolution of tetrapod fossoriality. It may be suggested that within a relatively short time interval following the Triassic-Jurassic extinction event, when environmental conditions were still marked by strongly seasonal climate with prolonged droughts as well as extreme moisture and temperature fluctuations, fossorial habit probably became yet again an endurance strategy for burrow makers.
... Certainly, vertebrates have been burrowing in Australian soil for more than 100 million years. For example, on the southern coast of Victoria, Martin (2009) identified three structures to be the first evidence suggestive of dinosaur burrows outside North America, and the oldest from the fossil record. The suspected burrows were similar to those of the only known burrowing dinosaur, Oryctodromeus cubicularis, which was found in Montana (USA) by Varricchio et al. (2007). ...
Research
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[This manuscript about Australian mammals is in draft and was last updated in 2014. It has not been peer-reviewed or published. I am unlikely to resume work on it, but please email me (pjrichards1@gmail.com) if you are interested in developing it.] Mammals have been influencing soil and landscape processes on the Australian continent for many millions of years. In the present day, in the marsupials and monotremes, Australia has a unique suite of native mammals. While many of these native mammals have been completely lost following European settlement, and many of the survivors are now severely reduced in number, they continue to make their mark on soils and landscapes. This review discusses the geomorphic actions of mammals such as the marsupial mole, wombat and burrowing bettong, as well as the European rabbit, which has taken the place of the bilby and other natives as a widespread bioturbator. Another drastic change in Australia’s mammal population occurred thousands of years ago with the extinction of Australia’s Pleistocene megafauna. In the present day, large introduced mammals such as feral horses, camels and water buffalos probably occupy similar ecological niches as the megafauna and might have similar geomorphic impacts. The review highlights changes in Australia’s geomorphologically significant mammal populations over time, particularly those brought about by human activity, with a focus on those mammals that burrow.
... Digging is a behavior that has only recently been explored in dinosaurs (Bakker, 1996;Senter, 2005Senter, , 2007Varricchio et al., 2007;Martin, 2009;Sereno, 2010;Simpson et al., 2010;Fowler and Hall, 2011;Huh et al., 2011). For example, the basal ornithopod Oryctodromeus cubicularis was described as potentially constructing burrows with its forelimbs due to its discovery in a burrow structure and morphological features potentially advantageous for digging, such as expanded and fused premaxillae, an expanded sacrum and a greater attachment area between the pelvis and sacrum relative to other basal ornithopods, and a robust, fused scapulocoracoid with a prominent scapular spine (Varricchio et al., 2007). ...
Article
The basal ornithopod Oryctodromeus cubicularis was described as burrowing due to its discovery in a burrow structure, and the presence of several morphological features considered consistent with burrowing. Using traditional and geometric morphometric analyses, the morphology of the humerus and scapula of ornithopods, basal ornithischians, and marginocephalians was analyzed to describe and characterize quantitatively the differences between Oryctodromeus and other ornithopods. These differences were then compared with the morphological adaptations for digging in mammals, because there are no adequate analogues for burrowing in extant archosaurs. A canonical variates analysis was also conducted on the geometric morphometric data to determine if phylogeny impacted morphological trends. The humerus of Oryctodromeus is slightly more robust than other basal ornithopods, indicating an adaptation for increased force applied to the humerus. The scapula provides the most compelling morphological support for digging in Oryctodromeus. The large acromion process and prominent scapular spine of Oryctodromeus, as well as the large posteroventrally expanded scapular blade, distinguish the scapula of Oryctodromeus from those of other ornithopods and would have provided surface areas for the attachment of the supracoracoideus, deltoideus clavicularis, and deltoideus scapularis muscles, the latter of which is important in digging in mammals. These features provide evidence for specialization for producing burrows by scratch digging.
... 땅에 구멍을 파는 육상동물에 의한 서관 구조는 페름기 초기의 지층으로부터 보고되어 있다 (Hasiotis, 1993). 이와 함께 최근에는 소형 공룡 의 서관 구조가 백악기 육성 퇴적층으로부터 보고된 바 있다 (Varrichio et al., 2007;Martin, 2009 Smith, 1987;Groenewald et al., 2001;Miller et al., 2001;Hasiotis et al., 2004Martin, 2001Hasiotis et al., 2004;Gobetz, 2006;Gobetz and Martin, 2006;Hasiotis, 2008 Voorhies, 1975;Hasiotis, 2002;Hasiotis et al., 2007 (Schult and Farlow, 1992;Hasiotis et al., 1993Hasiotis et al., , 2004Hasiotis et al., , 1999Meyer, 1999;Hembree et al., 2004;Buatois and Mángano, 2011;Knaust and Bromley, 2012). 일반적으로 육 상 척추동물들이 땅 속에 서관 구조를 짓는 것은 지 표 환경에서의 기온 변화나 강우, 포식자 등에 의한 위협 요소로부터의 피난처를 마련키 위한 것으로 (Butler, 1995;Groenewald et al., 2001; (Groenewald et al., 2001). ...
... Miller et al., 2001;Sidor et al., 2009) and in Australia (e.g. Martin, 2009). These structures were found completely fi lled with sediments; attain maximum diameters of 0.5 m and lengths of up to 5.5 m. ...
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In the neighborhood of the city of Boqueirdo do Leao (State of Rio Grande do Sul, Brazil) a set of three big-sized tunnels has been found. One of the tunnels is only partially filled with sand and accessible along its entire length. It is horizontal, slightly sinuous, 36 m long, up to 4.2 m wide and up to 2.0 m high. The surface morphology of the walls is composed of anthropogenic marks, speleothems, black incrustations and traces like digging scratches and smoothed surfaces. The 2'd tunnel has its entrance blocked by sand and sandstone cobbles, but the end of the tunnel is only partially clogged and therefore accessible. This accessible portion is 12 m long, 3 m wide and 1.5 m high. The 3rd tunnel is completely filled and collapsed and is nowadays only indicated by concave roof features at its end. The general features of the tunnel system and the analysis of the surface morphology of the walls of the accessible portions permit to conclude that the tunnels were produced by ground sloths of the Cenozoic South American megafauna. The size of the tunnels suggests that its excavation was gradually carried out by successive generations of sloth herds, and not by a single individual animal. The primary function of the tunnels probably was not protection from predators, which had easy access to structures of this size, but to shelter during a drier climate. However, it is not yet possible to relate the tunnels to a specific ground sloth genus, a task that depends on the discovery of better-preserved tunnel systems.
... Although vertebrate ichnology has traditionally been limited to the study of tracks and trails (e.g., Peabody 1954;Sarjeant 1975;Currie 1983;Lockley et al. 1994;Irby and Albright 2002;Kubo and Benton 2009), vertebrate trace fossils also include complex and varied burrow structures (e.g., Martin and Bennett 1977;Smith 1987;Groenewald et al. 2001;Hembree et al. 2004;Gobetz and Martin 2006;Hembree and Hasiotis 2008) . Burrowing behavior has evolved independently in several vertebrate clades, and vertebrate burrows are well represented in the geologic record with the earliest recognized burrows dating to the Early Devonian (e.g., Romer and Olson 1954;Damiani et al. 2003;Hasiotis 2003;Hasiotis 2004;Martin 2009). Despite the early appearance and persistence of vertebrate burrows in the geologic record, few researchers have studied the biogenic structures and sediment interactions of extant continental vertebrates (Voorhies 1975;Hasiotis et al. 2007). ...
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Neoichnological experiments involving a species of tropical, ground-dwelling skink, Mabuya multifasciata, demonstrate the diversity of biogenic structures produced by medium-sized lizards. Although the majority of skinks are ground dwellers or burrowers, little is known about the biogenic structures produced by this most diverse group of lizards. The documentation of biogenic structures produced by M. multifasciata will aid in the identification of trace fossils produced by skinks, help to improve the fossil record of these difficult-to-preserve animals, and allow for more complete paleoecological and paleoenvironmental reconstructions. Skinks were placed in terrariums filled with sediment of varying compositions and moisture content and were allowed to burrow. Open burrows were cast with plaster, photographed, measured, and statistically analyzed. The skinks produced seven distinct burrow morphologies including various ramps, U-, and J-shaped burrows. While there was no direct correlation between burrow properties and sediment properties, the burrows showed some variations due to the changes in sediment density and moisture content. The burrows had greater average complexities and tunnel heights when the sediment moisture was increased, whereas they had lower average widths and circumferences when the sediment density was increased. The data collected in this study can be directly applied to terrestrial trace fossil assemblages in tropical paleosols to better interpret their paleoecology and assess paleoenvironmental conditions.
... Terrestrial tetrapod burrows have been described from a number of fluvial and aeolian successions dating from the present day back to the Devonian (e.g. Barbour 1895;Olson & Bolles 1975;Voorhies 1975;Martin & Bennett 1977;Smith 1987;Hasiotis et al. , 2004Groenewald et al. 2001;Miller et al. 2001;Damiani et al. 2003;Hembree et al. 2004;Loope 2006Loope , 2008Colombi et al. 2008;Hembree & Hasiotis 2008;Sidor et al. 2008;Martin 2009;Schmeisser et al. Permian and Lower-Middle Triassic burrows were, until now, only known from south-western Gondwana. ...
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Krapovickas, V., Mancuso, A.C., Marsicano, C.A., Domnanovich, N.S. & Schultz, C.L. 2013: Large tetrapod burrows from the Middle Triassic of Argentina: a behavioural adaptation to seasonal semi-arid climate? Lethaia, Vol. 46, pp. 154–169. We report the discovery of large burrow casts in the early Middle Triassic Tarjados Formation, at Talampaya National Park, north-western Argentina. Facies analysis indicates the burrows are preserved in sandbars deposited by an ephemeral river under semi-arid and seasonal climatic conditions. The structures are mostly preserved in longitudinal cross-section and consist of an opening, an inclined tunnel (ramp), and a terminal chamber. The ramp is 8–14 cm in height, up to 130 cm in length and penetrates 49–63 cm bellow the palaeosurface with an inclination of 22°–30°. We studied burrow cast dimensions, overall architectural morphology, surficial marks, and compared them with other large burrows of both invertebrate and vertebrate origin. A tetrapod origin of the burrow casts was established based on: distinctive architecture, and size, which is more than twice the most common size range for large terrestrial invertebrate burrows. Comparison with other Upper Permian and Triassic tetrapod burrows allows us to identify three general morphological groups: (1) simple inclined burrows; (2) helical burrows; and (3) burrow network complexes, representing different behaviours. A study of tetrapod body fossils preserved within other Upper Permian and Triassic burrows shows that the Tarjados structures were most likely produced by non-mammalian cynodonts. The environmental and climatic context suggests that aridity and seasonality played a fundamental role selecting burrowing behaviour in therapsids and that by the Early–Middle Triassic their burrowing behaviour attained a complexity comparable to modern mammals. □Argentina, behaviour, palaeoclimate, Permo-Triassic, Tarjados Formation, Tetrapod burrows.
... Similarly, three enigmatic structures (sans body fossils) in Australia have been interpreted as Cretaceous burrows of hypsilophodontid-grade dinosaurs. These burrows may represent adaptation to polar environments (Martin, 2009), supporting inferences drawn from body fossils (Thulborn, 1978). ...
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Minimal direct evidence exists in the rock record of dinosaurs and mammals behaving as predators and prey, respectively. A newly discovered Late Cretaceous trace fossil association of digging traces of maniraptoran theropod dinosaurs and mammalian den complexes indicates a predator-prey relationship. Three distinct associated trace fossils occur within a floodplain siltstone-mudstone bed of the Upper Cretaceous Wahweap Formation in southern Utah, United States. One trace fossil morphology and its extramorphological variants record digging by a maniraptoran theropod dinosaur, possibly a dromeosaurid or troodontid. The other two are interpreted as mammalian den complexes. The proximal association of these trace fossils suggests that dinosaurs used excavation techniques to prey on mammals.
... Many different morphological characteristics have been utilized to identify potential architects of continental burrows including overall burrow architecture, superficial markings, dimensions, spatial relationships, and resemblance to known tetrapod burrows [4,5,71,74]. The architectural and superficial morphologies described for Morphotypes 1 and 2 above indicate the burrows were likely constructed by tetrapods. ...
... Presence of zonal bone was interpreted to mean that the theropod likely hibernated during the severe winters, whereas the absence of zonal bone in the hypsilophodontid suggested that it remained active and continued to grow throughout the winter [8]. This hypothesis continues to influence interpretations of polar dinosaur behavior and physiology (e.g., [11,12131415). Since that initial study, the number of hypsilophodontid fossils collected from Victoria has increased substantially, thus permitting a larger sample for osteohistologic examination. ...
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Analysis of bone microstructure in ornithopod and theropod dinosaurs from Victoria, Australia, documents ontogenetic changes, providing insight into the dinosaurs' successful habitation of Cretaceous Antarctic environments. Woven-fibered bone tissue in the smallest specimens indicates rapid growth rates during early ontogeny. Later ontogeny is marked by parallel-fibered tissue, suggesting reduced growth rates approaching skeletal maturity. Bone microstructure similarities between the ornithopods and theropods, including the presence of LAGs in each group, suggest there is no osteohistologic evidence supporting the hypothesis that polar theropods hibernated seasonally. Results instead suggest high-latitude dinosaurs had growth trajectories similar to their lower-latitude relatives and thus, rapid early ontogenetic growth and the cyclical suspensions of growth inherent in the theropod and ornithopod lineages enabled them to successfully exploit polar regions.
Article
A treasure trove of dinosaur bones and teeth from Northern Alaska — many from juveniles and yearlings — reveals that dinosaurs lived year-round in the cold and dark environment of the high Arctic.
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The Upper Cretaceous 'upper' Winton Formation of Queensland, Australia is world famous for hosting Dinosaur Stampede National Monument at Lark Quarry Conservation Park, a somewhat controversial tracksite that preserves thousands of tridactyl dinosaur tracks attributed to ornithopods and theropods. Herein, we describe the Snake Creek Tracksite, a new vertebrate ichnoassemblage from the 'upper' Winton Formation, originally situated on Karoola Station but now relocated to the Australian Age of Dinosaurs Museum of Natural History. This site preserves the first sauropod tracks reported from eastern Australia, a small number of theropod and ornithopod tracks, the first fossilised crocodyliform and ?turtle tracks reported from Australia, and possible lungfish and actinopterygian feeding traces. The sauropod trackways are wide-gauge, with manus tracks bearing an ungual impression on digit I, and anteriorly tapered pes tracks with straight or concave forward posterior margins. These tracks support the hypothesis that at least one sauropod taxon from the 'upper' Winton Formation retained a pollex claw (previously hypothesised for Diamantinasaurus matildae based on body fossils). Many of the crocodyliform trackways indicate underwater walking. The Snake Creek Tracksite reconciles the sauropod-, crocodyliform-, turtle-, and lungfish-dominated body fossil record of the 'upper' Winton Formation with its heretofore ornithopod-and theropod-dominated ichnofossil record.
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Vertebrate burrows from the Mesozoic of North America have been scarcely known. We report two different burrows (burrows A and B) produced by small animals in the Lower Cretaceous (Albian-Cenomanian) Mussentuchit Member of the Cedar Mountain Formation, Utah, USA .The burrow-bearing bed of the Mussentuchit Member consists of poorly-drained paleosols, and the burrows are infilled with ight-colored carbonate probably due to arise in a regional water table. Both burrows were found in-situ and inclined downwards. The burrow A is 60 cm long, and terminated in an expanded distal chamber, whereas the burrow B is100 cm long and branched, with some small expanded chambers in the middle of the tunnel. Both tunnels have the width to height ratio larger than 1.3. In the burrows, the external walls lack scratch marks, but do show localized, prominent bulges in the burrow A and divots at local expansions of the tunnel in the burrow B. These are unlike those reported from Triassic and Jurassic vertebrate burrows. The estimated weight of the excavators is 3.1g for the burrow A and 6.8-17.8 g for the burrow B based on the area of each tunnel, indicating that both trace makers were small animals. A bulge in the burrow B was possibly left by tip of the excavator's head, as seen in the burrows of modern fossorial squamates. The discovery of a potential squamate burrow from the Cedar Mountain Formation of Utah is consistent with the oldest body fossils of skinks and snakes from the Early Cretaceous.
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The great majority of researchers concur that the presence of dinosaurs near the poles of their time are part of a large body of evidence that all Cretaceous dinosaurs had elevated metabolic rates more like their avian subbranch and mammals than low-energy reptiles. Yet a few still propose that nonavian dinosaurs were bradyenergetic ectothermic reptiles, and migrated away from the polar winters. The latter is not biologically possible because land animals cannot and never undertake very long seasonal migrations because the cost of ground locomotion is too high even for long limbed, tachyenergetic mammals to do so, much less low-energy reptiles. Nor was it geographically possible because marine barriers barred some polar dinosaurs from moving towards the winter sun. The presence of external insulation on some dinosaurs both strongly supports their being tachyenergetic endotherms and helps explain their ability to survive polar winters that included extended dark, chilling rains, sharp frosts, and blizzards so antagonistic to reptiles that the latter are absent from some locations that preserve dinosaurs including birds and mammals. The hypothesis that nonavian dinosaurs failed to survive the K/Pg crisis because they had reptilian energetics is illogical not only because they did not have such metabolisms, but because many low-energy reptiles did survive the crisis. The global super chill that apparently plagued K/Pg dinosaurs should have seriously impacted dinosaurs at all latitudes, but does not entirely readily explain their loss because some avian dinosaurs and other land tetrapods did survive. High- as well as low-latitude dinosaurs add to the growing evidence that high-energy endothermy has been a common adaptation in a wide variety of vertebrates and flying insects since the late Paleozoic.
Chapter
Vertebrate burrows are common trace fossils in paleosols. Size, surface morphology and remains are some criteria to distinguish invertebrate from small vertebrate burrows. Basic types comprise vertical, vertical with terminal chamber, inclined, inclined with terminal chamber, helical, horizontal networks and inclined boxworks. Lungfishes, amphibians, reptiles, dinosaurs, and mammals are the most common producers. Descriptions of fossil and extant vertebrate burrows are scattered in the biological, paleontological and ichnological literature, including some partial reviews on fossil examples. In comparison with the unnamed cases, there are few ichnotaxa described, including Torridorefugium, Kladosystemites, Daemonelix, Alezichnos, Nagtuichnus, Polychoredrites, and Katarrhedrites, which are reviewed. Megaburrows corresponding to large mammals are also discussed. Also common in paleosols, root traces have been always treated as a distinct item in ichnology because of their plant origin. Different approaches to its treatment are reviewed. Particular cases of rhizoliths, drab-haloed root traces, rhizohaloes, megarhizoliths, paleorhizospheres and rhizolith balls are reviewed. Megarhizoliths, paleorhizospheres and false termite nests. A blueprint-style plate concentrates significant trace fossils produced by vertebrates in paleosols. Color plates of extant and fossil traces and morphological details are provided.
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Martin, A.J. 2016. A close look at Victoria's first known dinosaur tracks. Memoirs of Museum Victoria 74: 63–71. Lower Cretaceous (Aptian-Albian) rocks of Victoria, Australia are well known for their dinosaur body fossils, but not so much for their trace fossils. For example, the first known dinosaur track from the Eumeralla Formation (Albian) of Knowledge Creek, Victoria, was not discovered until 1980. This specimen, along with two more Eumeralla tracks found at Skenes Creek in 1989, constituted all of the dinosaur tracks recognised in Lower Cretaceous strata of southern Australia until the late 2000s. Unfortunately, none of these first-known dinosaur tracks of Victoria were properly described and diagnosed. Hence, the main purpose of this study is to document these trace fossils more thoroughly. Remarkably, the Knowledge Creek and one of the Skenes Creek tracks are nearly identical in size and form; both tracks are attributed to small ornithopods. Although poorly expressed, the second probable track from Skenes Creek provides a search image for less obvious dinosaur tracks in Lower Cretaceous strata of Victoria. The Skenes Creek tracks were also likely from the same trackway, and thus may represent the first discovered dinosaur trackway from Victoria. These tracks are the first confirmed ornithopod tracks for Victoria, augmenting abundant body fossil evidence of small ornithopods ('hypsilophodontids') in formerly polar environments during the Early Cretaceous.
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Concretions are an important source of soft-bodied fossils. In order to determine the controls on exceptional fossilization within concretions, we scored 88 concretion-bearing sites for 11 environmental and compositional variables together with presence/absence of soft-tissue preservation and analyzed their relationships using multiple correspondence analysis (MCA) and qualitative logistic regression. Sites yielding exceptional fossils were distributed randomly through the 88 examples considered, suggesting that exceptional preservation can occur in almost any environment where concretions form. The patterns of interaction of the variables in the MCA revealed that the most important factors controlling exceptional preservation in concretions are related to (1) the potential for fossil preservation in the broader depositional setting (i.e., how likely fossils are to be preserved without concretions but in the same depositional environment) and (2) the rate of concretion growth. In an analysis of the contribution of individual variables, logistic regression showed that two features correlate with the presence of soft-tissue preservation in concretions: (1) fine-grained host lithology, and (2) relatively constant δ13C values. The role of the first of these can be tested experimentally. Decay experiments on fish tissue in glass beads of three different sizes and therefore of different permeability showed that decay is inhibited, and mineral precipitation enhanced, in low-permeability sediments. Thus a process of positive feedback promotes exceptional preservation where early cementation results in a rapid decrease in permeability during concretion formation. The second feature, a relatively constant δ13C trend, suggests that certain patterns of concretion growth, pervasive growth or concentric growth with one growth layer, are more conducive to fossilization than others.
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1); Francisco Sekiguchi de Carvalho Buchmann(2); Leonardo Gonçalves de Lima(1); Felipe Caron(1); Renato Pereira Lopes(3) & Milene Fornari(4) Resumo As paleotocas, que são túneis escavados por mamíferos extintos da Megafauna Sul-Americana, podem ser encontradas às centenas no Sul e Sudeste do Brasil. Os túneis atingem 4,0 metros de largura, 2,0 metros de altura e podem ocorrer interligados, somando comprimentos que superam várias centenas de metros. Seu estudo exige uma abordagem interdisciplinar, tendo em vista que oferecem subsídios para projetos científicos de Paleontologia de Vertebrados, Palinologia, Biotecnologia, Arqueologia, Espeleologia, Biologia, Paleoclimatologia, História e Turismo. Individualmente, as paleotocas normalmente não contemplam todas essas áreas de conhecimento ao mesmo tempo. Entretanto, há excelentes exemplos de paleotocas que oferecem subsídios científicos em cada uma das áreas. Nossa perspectiva, a médio e longo prazo, é do descobrimento de uma série de novas ocorrências nas quais todos esses ramos da Ciência e possivelmente outros precisam ser considerados e podem ser explorados. Abstract Palaeovertebrate tunnels, excavated by the South American Megafauna, can be found to the hundreds in the Southern and Southeastern regions of Brazil, to our current knowledge. The tunnels reach widths of up to 4,0 meters, heights of up to 2,0 meters and may occur interlinked, with summed lengths of several hundred meters. The study of these tunnels require an interdisciplinary approach, due to the fact that they offer scientific research possibilities in Vertebrate Paleontology, Palinology, Biotechnology, Archaeology, Speleology, Biology, Palaeoclimatology, History and Tourism. Individually, most palaeovertebrate tunnels do not apply to all of these fields, but there are excellent examples of tunnels that allowed data collecting in each one of these sciences. Our perspective, in the medium and long term, is of the discovery of many new occurrences whose study has to consider all these fields of human knowledge and possibly other ones too, which may be explored.
Book
In 1837 a young Charles Darwin took his notebook, wrote “I think”, and then sketched a rudimentary, stick-like tree. Each branch of Darwin’s tree of life told a story of survival and adaptation – adaptation of animals and plants not just to the environment but also to life with other living things. However, more than 150 years since Darwin published his singular idea of natural selection, the science of ecology has yet to account for how contrasting evolutionary outcomes affect the ability of organisms to coexist in communities and to regulate ecosystem functioning. In this book Philip Grime and Simon Pierce explain how evidence from across the world is revealing that, beneath the wealth of apparently limitless and bewildering variation in detailed structure and functioning, the essential biology of all organisms is subject to the same set of basic interacting constraints on life-history and physiology. The inescapable resulting predicament during the evolution of every species is that, according to habitat, each must adopt a predictable compromise with regard to how they use the resources at their disposal in order to survive. The compromise involves the investment of resources in either the effort to acquire more resources, the tolerance of factors that reduce metabolic performance, or reproduction. This three-way trade-off is the irreducible core of the universal adaptive strategy theory which Grime and Pierce use to investigate how two environmental filters selecting, respectively, for convergence and divergence in organism function determine the identity of organisms in communities, and ultimately how different evolutionary strategies affect the functioning of ecosystems. This book reflects an historic phase in which evolutionary processes are finally moving centre stage in the effort to unify ecological theory, and animal, plant and microbial ecology have begun to find a common theoretical framework.
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Although burrowing ability has been widespread in tetrapods for more than 300 million years, subsurface dwelling structures that indicate communal behavior are poorly evidenced from pre-Cenozoic strata. Here we present recently discovered tetrapod burrows from Middle Triassic red beds of the Argana Basin in central Morocco, whose complexity suggests an origin by gregarious animals. The well-preserved burrows occur in interbedded mudstones and sandstones interpreted as channel and overbank deposits of ephemeral, braided streams. All burrows originate from the top of thick-bedded sandstones and descend as moderately inclined (106–306), partially spiral tunnels to laterally extended, branched chambers in underlying mudstones. Tunnel segments are biconvex to planoconvex in cross section, up to 20 cm wide and 12 cm in maximum height and exhibit transverse scratch marks along the ceilings and sidewalls. Distinctive burrow characteristics include a laterally sinuous geometry (wavelength l 5 38–45 cm; amplitude A 5 5–10 cm) of the tubelike passages and the presence of grouped alcoves in terminal chambers. We attribute the burrows to procolophonids or therapsids based on closely associated tetrapod tracks and the limited diameter of the excavations. Our findings represent the second oldest record of communal fossorial behavior by tetrapods and the oldest example from low-latitude areas. Beyond providing refuge from predators, these elaborate underground structures probably functioned as a buffer against diurnal or seasonal variations of air temperature and humidity in a semiarid habitat that was situated just north of the paleoequator.
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Coburg Island and neighbouring waters were recently designated a Canadian National Wildlife Area. The large seabird colony at Cambridge Point has been previously described, and is dominated by Thick-billed Murres (160 000 pairs). We found that a small offshore island, named Princess Charlotte Monument, also supported breeding populations of seven marine bird species; three of which did not breed at the main colony (i.e., Northern Fulmar, Common Eider, and Atlantic Puffin). This is the most northern confirmed breeding site for Atlantic Puffins in Canada. Puffins at both Coburg Island and northern Greenland nest in rock crevices, apparently because permafrost in soil prevents burrow nesting. We suggest that puffin populations in the high arctic may be limited by habitat, rather than prey availability.
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Sedimentary structures resembling casts of lungfish burrows occur locally in the Upper Triassic Redonda Formation (Chinle Group) at Mesa Redonda, Quay County, New Mexico. The casts are densely concentrated over an area of about 5m 2 in a very fine-grained sandstone that represents a lacustrine margin sheetflood facies. Cylindrical cross-section and relatively large diameter (4.8-7.2 cm) indicate burrowing excavation by a single organism, most likely a vertebrate. Identification of these structures as root casts is ruled out by lack of secondary branches and overall size. No skeletal remains have been recovered, yet comparison with fossil and modern traces indicates a close similarity to burrows of lungfish. Diagnostic features include diameter within the range of previously described burrows containing lungfish skeletons, weathering into checker-like discs, and differentially-weathered fill layers. The burrows are devoid of surficial morphology except for spiraling and infilled mudcracks, which also occur on other fossilized lungfish burrows from the Chinle Group and from the Lower Permian of Texas and Kansas. Reduction/oxidation (redox) features in burrow fill and in the surrounding sediment indicate periodic (seasonal) water-logging and drying of the substrate with fluctuating lake level. The Mesa Redonda burrows have helical architecture, varying from short helices to angled shafts with a flask-shaped terminus, to very shallow excavations that widen upward. Previously described fossil lungfish burrows are identified as aestivation tunnels, with vertical morphology and occasional flask-shaped chambers. Aestivation and breeding tunnels vary within and among living lungfish species due to soil properties and other physical parameters , and these may also account for differences in fossil burrow morphology. The obliquely-angled shafts of some of the Mesa Redonda burrows, in addition to pronounced helical and sinuous architecture, may indicate nesting or spawning in relatively simple tunnels, in addition to aestivation.
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Two types of large diameter burrows, recognized by non-overlapping size distributions, occur in high paleolatitude floodplain deposits of the Lower Triassic Fremouw Formation, Shackleton Glacier area, Antarctica. Type G (giant) burrows are gently dipping tunnels 8 to 19 cm in diameter. Type L (large) burrows are 2 to 6.5 cm in diameter, curved or subhorizontal tunnels that rarely branch; scratch markings on both burrow types generally are parallel or tangential to the long axis of the burrows. Type G burrows are interpreted as produced by tetrapods based on similarity in size, architecture, and surface markings to Permian burrows from South Africa that contain complete skeletons of therapsids. These are the first tetrapod burrows described from Antarctica. Type L burrows have characteristics of both fossil tetrapod and crayfish burrows, precluding identification of an unique producer. Triassic tetrapods, including therapsids, that lived in high southern latitudes probably burrowed to dampen the effects of seasonal environmental fluctuations, just as do many of their mammalian counterparts living today in high latitudes. The paleolatitudinal and paleooclimatic distributions of burrowing therapsids and their mammalian descendents can be assessed by focusing search efforts on very large burrows, and by identifying producers using criteria delineated herein; this will clarify the extent to which the burrowing habit originated and persisted in high latitudes.
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A study of spores and pollen assemblages from vertebrate fossil localities in the nonmarine Otway and Strzelecki Groups, Victoria, has shown that the localities in Otway Group sediments are of late Aptian- early Albian age (Crybelosporites striatus Subzone of Dettmann & Playford 1969) and the localities of the Strzelecki Group of Valanginian - Aptian age (Cyclosporites hughesii Subzone of Dettmann & Playford 1969). This age determination is dependent on the isochronicity of spore-pollen zones across eastern Australia. -Authors
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A small collection of hypsilophodontid dinosaurs consisting primarily of isolated bones and teeth, has been made over the past two decades from the late Early Cretaceous coastal outcrops in southeastern Australia. Fragmentary though the bulk of this material is, on dental evidence it is possible to recognize three different genera and species Leaellynasaura amicagraphica, Atlascopcosaurus Ioadsi and Qantassaurus intrepidus gen. et sp. nov. The femora are allocated to L. amicagraphica and Fulgurotherium australe. The femora of F. australe show a marked diversity in size and shape suggesting that when the material assigned to this form species is better known, it could well be divided into three or more genera.
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When water froze over, Alligator mississippiensis retained access to air by a 'submerged breathing' posture in which the snout broke the water (ie ice) surface while the remainder of the head and the body angled back down into the den. -P.J.Jarvis
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The recovery of abundant dinosaur fossils from high paleolatitudes of northern Alaska has raised some hard questions in relation to any available model of dinosaur physiology. To explain the occurrence of hadrosaurs at high ancient latitudes, a model involving long-distance migration analogous to that of the modern caribou has been proposed. The model calls for seasonal movements over great latitudinal distances by these Cretaceous hadrosaurs. This model is reassessed in terms of the growth, body sizes, and inferred physiological ecology of the hadrosaurs and the caribou. Histological data suggest that juvenile hadrosaurs obtained from northern Alaska were greater than 1 year in age. Comparison of the relative sizes of juvenile and adult hadrosaurs with juvenile and adult caribou suggests, based on qualitative energetics, that the juvenile hadrosaurs were too small to participate in long-distance migration. The "hadrosaurs as caribou" model provides clues to the feeding ecology of North Slope hadrosaurs, if they are reinterpreted as year-round residents of high latitudes. However, it does not constitute a satisfactory basis on which to infer long-distance seasonal migrations by these animals. © 2001 OPA (Overseas Publishers Association) N.V. Published by license under the Harwood Academic Publishers imprint, part of Gordon and Breach Publishing a member of the Taylor & Francis Group. All rights reserved.
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Putative crayfish trace fossils recently reported from Antarctica are likely small-to large-diameter burrows of therapsid vertebrates based on comparisons to other Permian and Triassic tetrapod burrows from South Africa. The Small and large-diameter burrows most likely belong to primitive mammal-like reptiles (therapsids) that constructed low-angle, elongate, and sometime spiralling tunnels. Similar burrows with associated therapsid body fossils occur in rocks that were deposited in alluvial environments in basins associated with Gondwana. This exercise in burrow identification stresses the importance of careful analysis of burrow morphologies, both in the outcrop and in the laboratory. Burrow signatures are useful for identifying a burrow architect only when 1) a large data base of specimens is available, 2) outcrop work details the 3-dimensional burrow architecture, and 3) comparisons are made to as many structures of burrowing organisms as possible.
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We report on the bone microstructure of a hypsilophodont and an ornithomimosaur from the Early Cretaceous, Otway Group of Dinosaur Cove in south-eastern Australia, which at the time lay well within the Antarctic Circle. Although subjected to the same environmental conditions, the dinosaurs exhibit different bone histology. The hypsilophodontid shows a continuous rate of bone deposition, while the ornithomimosaur has a cyclical pattern of bone formation. We interpret these varying patterns of bone microstructure as a reflection of different growth strategies of these dinosaurs.
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In south-central Utah, eolian cross-strata of the Escalante Member of the Entrada Sandstone contain inclined, cylindrical burrows up to 63 cm in diameter and 305 cm long. Of the 14 large tunnels located during this study, 12 descend from second- and third-order bounding surfaces that formed on the lee slopes of large dune ridges, well above the water table. The tunnels are inclined 15 degrees-22 degrees; one tunnel ends in an expanded chamber. Eolian cross-strata fill proximal portions of four of the tunnels and indicate that after abandonment, sand drifts migrated as much as a meter into the open shafts. Structureless sand and breccia blocks that were generated by roof collapse fill other tunnels. Animals dug the tunnels in rain-moistened, cohesive sand. The burrows may have served as temporary shelters from severe diurnal conditions in the shadeless, subtropical Entrada dune field.
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(25), followed by west (13), east (10), and north (8). Most dens were constructed under cover of tall (.0.5 m) shrubs (Betula glandulosa and Salix), the root structures of which supported ceilings of dens. Selection of denning habitat by bears was significantly different from random (G 5 127.67, d.f. 5 6, P , 0.0001). Bonferroni confidence intervals indicated that esker habitat was selected more than expected by chance (P , 0.10). Den entrance occurred primarily in last 2 weeks of October. The majority of bears emerged from dens in the 1st week of May.
Article
Polar bears (Ursus maritimus) give birth during mid-winter in dens of ice and snow. Denning polar bears subjected to human disturbances may abandon dens before their altricial young can survive the rigors of the Arctic winter. Because the Arctic coastal plain of Alaska is an area of high petroleum potential and contains existing and planned oil field developments, the distribution of polar bear dens on the plain is of interest to land managers. Therefore, as part of a study of denning habitats along the entire Arctic coast of Alaska, we examined high-resolution aerial photographs (n = 1655) of the 7994 km(2) coastal plain included in the Arctic National Wildlife Refuge (ANWR) and mapped 3621 km of bank habitat suitable for denning by polar bears. Such habitats were distributed uniformly and comprised 0.29% (23.2 km(2)) of the coastal plain between the Canning River and the Canadian border. Ground-truth sampling suggested that we had correctly identified 91.5% of bank denning habitats on the ANWR coastal plain. Knowledge of the distribution of these habitats will help facilitate informed management of human activities and minimize disruption of polar bears in maternal dens.
Cranial and postcranial remains from the Early Cretaceous (Aptian) of southeastern Australia appear to be from the last known members of the labyrinthodont Amphibia and to belong to the temnospondyl superfamily Brachyopoidea. Koolasuchus cleelandi n. gen. n.sp. lived well beyond the documented time of labyrinthodonts elsewhere in the world, perhaps protected by a polar "safe area" that excluded such competitors as the modern crocodiles. These late occurring Australian temnospondyls are always associated with coarser grained facies.
Chapter
Taphonomy, the study of fossilization, is an important element of paleontology. The processes that influence the potential for and the quality of body fossil preservation are diverse, and include those affecting organisms at the time of death (necrolysis), those operating in the interval between death and final burial (biostratinomic processes), and those impacting organism remains after burial (fossil diagenesis). These processes represent taphonomic filters that govern the degree to which fossil assemblages mirror original faunal communities and set limits on the accuracy of paleoecologic reconstructions. The taphonomic state of ichnofossil assemblages can be measured using two independent parameters: completeness of the preserved record of biogenic activity that occurred in a substrate (ichnologic fidelity); and degree of manifestation of the trace fossils that are preserved (trace fossil visibility). These parameters are controlled by environmental dynamics, tracemaker behavior and position in substrates, and a range of diagenetic processes (mechanical compaction, selective mineralization, lithification, and weathering). Consequently, trace fossil preservational modes can be exploited in the studies of depositional regimes, paleobiology, and post-depositional histories. Trace fossil assemblages characterized by relatively high ichnologic fidelity, trace fossil visibility, or both, may be particularly informative, and hence, can be considered as ichnofossil- lagerstätten.
Article
Skeletal remains of ceratopsian dinosaurs and a turtle, a dinosaur footprint, and tooth marks of a small carnivorous reptile on a freshwater clam show that the terrestrial vertebrate fauna of the Late Cretaceous of the North Slope of Alaska was moderately diverse in the Late Cretaceous. Paleobotanical evidence suggests that the climate was cool temperate and that mean annual temperature decreased through the Late Cretaceous. Winter temperatures were likely to have been below freezing for at least short intervals. Dinosaurs either could have overwintered on the North Slope or migrated. So long as freezing conditions were not long or severe, the reptiles are likely to have been able to survive the Late Cretaceous high-latitude winters, whether they were endotherms or ectotherms, because forage was richer and temperatures milder than the conditions faced by modern, high-latitude herbivores. Alternatively, the dinosaurs could have migrated with the 'sun line', possibly as far as the Cretaceous Arctic Circle, a distance of = or <2100 km, easily traveled by moving at a rate of 1 km/hr for 12 hrs/day. -from Authors
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Southern polar biotas of the Early Cretaceous (Valanginian-early Albian) of south-central Victoria, Australia, contain > 150 taxa of plants, invertebrates, and vertebrates, including dinosaurs, fish, possibly a labyrinthodont amphibian, turtles, lepidosaurs, pterosaurs, freshwater plesiosaurs, theropods, and birds, but thus far no crocodiles or mammals. The fossil-producing sediments are the Otway and Strzelecki Groups, which some authors combine into one unit, the Korumburra Group. They represent volcanogenic clays, silts, and sands deposited in several different facies of braided river systems that occupied a down-dropped graben created when Australia and Antarctica began to separate in the late Mesozoic. Periodicity in the sedimentation regime may have been related to meltwater floods in the austral spring. Invertebrates, plants, and geochemistry suggest that a cool, humid climate prevailed. paleomagnetic studies on the Otway Group indicate that southern Victoria was situated at a high latitude, between 70 and 85° south, in the late Early Cretaceous. -from Authors
Article
Sedimentary structures in the Early Cretaceous Wonthaggi Formation of southeastern Australia appear to have formed in the presence of seasonally frozen ground, indicating a frigid climate. Histological analysis of a hypsilophodontid dinosaur bone found 3 metres stratigraphically above one of the seasonally frozen ground horizons shows that this individual never experienced a period of slow growth as would have been the case had it not been active during the polar winter. Another of the southeastern Australian hypsilophodontids had enlarged optic lobes of the brain, perhaps an adaptation for enhanced visual acuity during the winter darkness, facilitating active foraging at that time.
Article
The Lower Cretaceous Koonwarra Fossil Bed, encountered in a road cutting S of Leongatha on the S Gippsland Highway, yielded >80 species of invertebrates. >70 are insects, associated with an ostracode, a syncarid (Koonaspides indistinctus gen. et sp.nov.), an anostracan and a cladoceran among the Crustacea, 2 spiders and a harvestman among the arachnids, possible earthworms, bryozoan statoblasts and a bivalved mollusc. The insects represent 12 orders dominated by the Hemiptera, Coleoptera and Diptera in terms of diversity but dominated numerically by aquatic immature Ephemeroptera and Diptera; Odonata, Blattodea, Plecoptera, Orthoptera, Psocoptera, Mecoptera, Trichoptera, Hymenoptera and probably Siphonaptera are lesser components. Insects are identified specifically and described taxonomically. However, the majority of the fauna is left in open nomenclature because features of generic or specific importance among living relatives are not clearly preserved on the fossils. The emphasis is on immature stages of the insect. The palaeoenvironment indicated by the invertebrate fauna is a shallow, semi-isolated body of water marginal to a shallow freshwater lake with periodic, probably seasonal, replenishing of the fauna from the lake and periodic mass-mortality of the isolated fauna; the mechanism for this mortality remains uncertain. A present-day environment in Lake Muirhead just E of the Grampians in W Victoria is suggested as possibly comparable to the fossil setting. -from Authors
Chapter
A large proportion of living vertebrates, particularly mammals, excavate burrows. At least half of the extant mammalian species are partially fossorial, and the habit has also been developed by many fishes, amphibians, reptiles, and even birds. Yet vertebrate burrows have rarely been reported as fossils. Possible explanations for this dearth of information or occurrences are: (1) lack of detailed observations, (2) tendency of burrowers to avoid areas of active sedimentation and (or) (3) an evolutionary increase in the burrowing habit as a result of Cenozoic climatic changes. The census of modern and fossil burrows and burrowers given herein emphasizes the potential paleoecological, paleoclimatic, and phylogenetic importance of fossil burrows.
Article
Options for overwintering success involve migration, hibernation and the evolution of means of resisting the harsh conditions. Changes in the physical nature of snow as it falls, settles, freezes and melts are shown. Plants need the means to acclimate to the cold, survive physiological drought (non-availability of free water), and to deal with a number of mechanical stresses. The evergreen habit is shown to be an important option. For animals, the basics of energy exchange are noted, and means of maintaining a warm body in a cold environment are examined, with consideration of physical versus physiological thermoregulation. Examination of the problem of appendages leads to evaluation of Bergmann's and Gloger's rules of size and colour, respectively; is it better to be large and white in a cold climate? Life under ice is described. A number of plant-animal interactions are noted, eg herbivore preferences and morphological and chemical plant resonses to winter browsing, and CO 2 build-up under snow and effects on subnivean animal activity. Finally, the response by humans to winter stress is outlined.-P.J.Jarvis
Article
Paleomagnetic evidence places southeastern Australia well inside the paleo-Antarctic Circle in the Early Cretaceous. Over the past two decades a small but moderately diverse dinosaur assemblage has been recovered from a variety of sediments laid down in a broad rift valley that was forming as Australia and Antarctica began separating at the beginning of the Cretaceous. The primary source of the sediments were volcanic vents that lay to the east on the Lord Howe Rise, east of Australia. A diverse flora of more than 150 species is associated with the dinosaur material. Analysis of this flora suggests a mean annual air temperature (MAAT) of + 7°C-+10'C. Oxygen isotope investigations suggest a lower MAAT (-2'C to + 5'C). Because of the discrepancy in the temperature estimates, the plants indicating a MAAT about equal to that of modern day Denver or Chicago on the one hand and the oxygen isotopes suggesting conditions more similiar to present day Fairbanks, Alaska, finding a third, independent way of assessing the MAAT has been a primary goal of the southeastern Australian polar dinosaur project. A third method of estimating temperature was found in 1996 when cryoturbation structures were recognized at four localities in the Strzelecki Group to the southeast of Melbourne, suggesting the former presence of seasonally frozen ground. These cryoturbation structures suggest MAAT of-6'C-+3'C. The lower limit is set by the absence of sand-or ice-wedges, which form only at a MAAT<-4'C. In
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Habitat selection by Chinese pangolin (Manis pentadactyla) in winter was studied in Dawuling Natural Reserve, Maoming City of Guangdong Province, China, from December 1999 through February 2001.The objective of this study was to determine the pangolin's habitat requirement in winter during poor environmental conditions. The dominant habitat of this Reserve was classified into 4 types, i.e. mixed coniferous and broadleaf forest (MCBF), evergreen broadleaf forest (EBF), coniferous forest (CF) and shrub forest (SF). The results showed that the ranking of vegetation types selected by pangolins in winter was MCBF > SF > EBF > CF. Pangolins preferred MCBF, and avoided CF. The environmental factors preferred by pangolins in winter were 30°-60° steep slopes, middle of slopes and bottom of slopes, sunny slopes, distance from human disturbance source exceeding 1 000 m with a minor disturbance degree, heavy (81 % - 100 %) undergrowth with good shelter conditions, moderate (760 - 1 500 m) elevation, and medium (31 % - 70 %) closure of arbor canopy. The surroundings factors avoided by pangolins were sharp slopes steeper than 60° or gentle slopes less than 30°, shady slopes, distance from human disturbance source within 1 000 m, dense (71 % - 100 %) or sparse (0 % - 30 %) closure of arbor canopy, medium or lower coverage (0 % - 50 %) of undergrowth, and the top of the slope. Pangolins preferred south-facing burrow entrances with thick cover, and avoided north-facing burrow entrances with bare or poor shelter. The thick layer of shrub and herbs growing under the tree canopy appeared to be especially important to pangolins during winter.
Article
We examined the energy saving and social interactions associated with winter huddling behavior in the muskrat, Ondatra zibethicus. At air temperatures of −10°C and 0°C, which encompass the lowest microclimate temperatures recorded from winter shelters, the resting metabolic rate of an aggregate of four muskrats averaged 11-14% below that of single animals. The minimal thermal conductance of the grouped animals was reduced by 8-10% over this same temperature range. Our findings suggest that communal nesting confers a modest, but potentially significant metabolic saving to overwintering muskrats.
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Theropod teeth are taxonomically diagnostic components of dinosaur assemblages. Seventy teeth have been recovered from six different localities in the Kogosukruk Tongue of the Prince Creek Formation (Upper Cretaceous) of the North Slope of Alaska. This assemblage of teeth shows slightly less diversity compared to well documented assemblages of teeth from the slightly older Judith River Formation of south-central Montana, the Aguja Formation of west Texas, and the Hell Creek Formation of eastern Montana. In addition, in contrast to the Judith River Formation assemblage of teeth in south-central Montana, the teeth assigned to Troodon dominated the Alaskan assemblage. The dominance of Troodon is attributed to adaptation by this theropod to low light conditions while over-wintering at a high paleolatitude.
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We measured gopher tortoises (Gopherus polyphemus) and their burrows from a population in central Florida. Burrows of most juveniles were excavated. Newly emerged hatchlings constructed burrows that had the same structure as the burrows of older juveniles. The cross-sectional shape of juvenile burrows was similar to that of adult burrows, although the latter tended to be proportionally wider. Differences in burrow shape between juveniles and adults were consistent with allometric changes in tortoise shape. Juvenile burrows had a significantly greater angle of declination than adult burrows. Regression analysis showed that relationship between carapace length and burrow width differed significantly between juveniles and adults.
Article
Seasonal changes in the microenvironment of Ondatra zibethicus in Delta Marsh, Manitoba, Canada, are described. In winter, well-insulated, closely-spaced resting and feeding shelters provided an equable microclimate moderated by the presence of open water in plunge holes. Group occupation of lodges during winter resulted in chamber temperatures that averaged 20°C above external air temperature. Daily fluctuations in winter lodge temperature reflected activity patterns of resident animals. In summer, high lodge temperatures (25 to 30°C) appeared to favor the use of burrows and open nests by adults. Burrows provided the coolest, most stable microclimate in summer, with temperatures ranging from 8.5 to 20.5°C, depending on soil depth. Between November 1973 and July 1975, air temperatures in the marsh ranged from −39 to 34°C, while temperatures recorded from within shelters used by muskrats varied from −9 to 30°C. The range of mean temperatures (3 to 25°C) recorded from within occupied lodges and burrows during this period approximated the thermoneutral zone of this species. It is suggested that energy costs for thermoregulation are minimized through the construction and selective use of multiple shelters.
Article
The Early Cretaceous Otway and Strzelecki Groups exposed on the southern coast of Victoria, Australia, have produced a fauna of dinosaurs that lived within the Antarctic Circle. As many as five or six species of hypsilophodontids numerically dominate the collections from there, but the rarer and more fragmentary theropod remains suggest a surprising diversity of carnivorous dinosaurs. A possible surangular and an isolated vertebra have characters considered diagnostic for Late Cretaceous oviraptorosaurs of the Northern Hemisphere. Other fossils suggest the presence of ornithomimosaurs, dromaeosaurids and neoceratopsians, and with the possible oviraptorosaur remains, challenge the widespread assumption that these animals originated on the northern continents.
Chapter
: The trace-fossil record of vertebrates contains behavioral evidence of fish, amphibians, reptiles, dinosaurs, mammals, and birds in continen-tal, transitional, and marine paleoenvironments since the Devonian. The study of vertebrate trace fossils includes tracks, trails, burrows, nests, and such feeding traces as bite marks, coprolites, gastroliths, and regurgitalites. Behaviors recorded by these traces include various kinds of (1) locomotion, (2) dwelling, (3) aestivation, (4) breeding and nesting, as well as (5) acts of feeding, which also result in (6) digestion, (7) regurgitation, and (8) defecation. These trace fossils represent the interaction between a vertebrate and a medium, which includes softgrounds, firmgrounds, hardgrounds, plants, and other animals. Humans also have a trace-fossil record, and, like other vertebrates, produce numerous trace fossils that result from different kinds of behavior.
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Data from two large (188 and 135 kg) male alligators (Alligator mississippiensis) indicated that 4-5 C seemed to be the lowest body temperatures that they could endure with subsequent recovery. Although one animal in shallow water managed to keep a breathing hole open for several days, in ice that was 1.5 cm thick, it later died following a decrease of its body temperature to 4.0 C. The second alligator which was located in a deeper portion of the reservoir used both terrestrial and aquatic basking behavior to raise its body temperature and level of activity. Except in the case of basking events, there was not clear evidence of significant evaluations of the body temperatures of either the live or dead alligators above those of their adjacent water. When located side-by-side, diurnal cycles of deep body temperatures exceeding adjacent water temperatures to a maximum extent near dawn and usually falling below water temperatures during the afternoon and early evening hours. The physical properties and thermal inertia of the bodies of such large alligators, when placed in appropriate microclimates, may be sufficient in themselves to explain the general patterns and levels of body temperature changes observed at these low temperatures.
Article
Body-mass estimates have been made for 220 of the over 300 generally accepted dinosaur genera. The 1–10 ton body-mass category is the modal one for all dinosaur genera, dinosaurs on nearly every continent, dinosaurs during most stages of the Mesozoic, and dinosaurs in two of the three peak historical periods of dinosaur discoveries. Carnivorous dinosaurs were much smaller than herbivores during the Late Jurassic and again in the Late Cretaceous: at other times the two were roughly equivalent in mass. In terms of discovery of dinosaur genera over time, there has been a simultaneous increase in proportion of very small (under 10 kg) dinosaurs and a relative decline in giant dinosaurs (10–100 tons). This suggests that early researchers tended to collect giant dinosaurs.
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The growth of many of the most familiar microorganisms is inhibited by temperatures lower than 10° C. The cause of growth inhibition in these mesophilic microorganisms may be the failure of regulatory systems, ribosome misfunction, or limited membrane permeability. Other (psychrophilic) microorganisms can grow in, or indeed require, lower temperatures than the mesophiles. Many psychrophiles are found in the ocean, the great bulk of whose waters have temperatures of less than 5°C. Other microorganisms can grow in food or concentrated solutions at temperatures down to −10°C. Scattered reports of growth at considerably lower temperatures may not be valid. So far as is known, a range of only about 30°C exists between the lowest and highest temperatures permitting the growth of practically any microorganism. Mechanisms that permit growth at low temperatures and that limit the overall range of growth are discussed. Some ecological niches in which water may remain liquid at very low temperatues are described. The possibilities for extraterrestrial life in such niches and some of the difficulties in demonstrating such life are discussed.
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The existing data on Late Mesozoic and Cenozoic seafloor spreading isochrons and fracture zone trends provide the basis for 12 reconstructions of the seafloor around Australia. The major changes of plate geometry in the Jurassic, Early Cretaceous, mid-Cretaceous, early Paleocene and early Eocene reflect global events. The pattern of spreading around Australia was determined by two long-standing (earlier Phanerozoic) factors that operated in a counter-clockwise direction: 1) penetration from the northwest by the Tethyan divergent ridge; and 2) rotation from the northeast of the Pacific convergent arc and back-arc. -from Authors
Article
Burrows of the lysorophid amphibian Brachydectes elongatus occur in deposits interpreted as ephemeral ponds within the Lower Permian Speiser Shale of eastern Kansas. The burrows of B. elongatus have been previously recorded in the Lower Permian strata of Texas, Oklahoma, and Kansas, but have not been described in detail and an ichnotaxonomic designation has not been provided. Torridorefugium eskridgensis new ichnogenus and ichnospecies show two types of burrow architecture distinguished by width-to-length ratios. Type I burrows are elongate, elliptical tubes 4–32 cm long and 2–7 cm wide. Type II burrows are short, elliptical tubes 1.5–3.5 cm long and 2.5–5 cm wide. Both Type I and II burrows may contain coiled skeletons of B. elongatus. Torridorefugium eskridgensis occur in clusters of up to 45 burrows with maximum concentrations of 20/m2. The type specimens of Torridorefugium eskridgensis occur in a 40-cm-thick lens of calcareous mudstone that fills a 100-m-long paleodepression within a well-developed paleosol. The burrow clusters are capped by surfaces with evidence of subaerial exposure, and overlain by nonburrowed, massive mudstone containing the fossils of the charophyte Stomachara, the ostracodes Carbonita and Paraparchites, fish, amphibians, and reptiles. This succession suggests that lysorophids burrowed in response to episodic, perhaps seasonal, droughts on the Permian midcontinental coastal plain. Permian lysorophid burrowing behavior is analogous to that of the extant aestivating amphibians Amphiuma sp. and Siren intermedia that inhabit ephemeral rivers and ponds of the southeastern United States.