Large Carnivore Footprints from the Late Pleistocene of Argentina

The aim of the present contribution is to describe large felipedid footprints from a new ichnological site from the Late Pleistocene of Buenos Aires Province, Argentina. The prints are referred as the new ichnospecies Felipeda miramarensis nov. ichnosp. Based on size and morphology, this new ichnotaxon may have been produced by the large machairodontine felid Smilodon populator. Track analysis indicates that the producer of the tracks had fully retractile claws, a plantigrade feet, and lacked strong supination capabilities on pes and manus. The size and depth differences between manus and pes prints indicate that the producer had notably robust anterior limbs. If correctly assigned, the new ichnospecies reinforces the idea that Smilodon was an ambush predatory mammal.     

Unusual aetosaur armor from the Upper Triassic of West Texas,U.S.A.

We report two unusual aetosaur scutes from the Tecovas Member of the Dockum Formation, Chinle Group (upper Carnian) of Crosby County, Texas, U.S.A. Originally collected by University of Michigan expeditions in the 1920’s, these scutes cannot be assigned with certainty to any known species of aetosaurs known from the American Southwest. One of these scutes may be a cervical horn ofParatypothorax, and if so confirms the similarities of this aetosaur toDesmatosuchus in the possession of horned lateral spikes. The other is a paramedian scute of a new aetosaur taxon inadequately known at present to be assigned a formal name. These scutes indicate that aetosaurs were more diverse in the Chinle Group than currently known, but do not alter the robust Late Triassic biochronology based on aetosaurs.     

A Revised Systematic Ichnotaxonomy and Review of the Vertebrate Footprint Ichnofamily Chirotheriidae from the British Triassic

Since 1838, many discoveries of the tetrapod footprint taxon Chirotherium and closely similar forms have been reported from the British Middle Triassic. These have been assigned to dozens of ichnotaxa, so that the identification and interpretation of members of the ichnofamily Chirotheriidae have become confused.

Part 1 of this article deals with ichnotaxonomy. Revision of all the available material shows that there are at least three valid ichnospecies of Chirotherium, one of Synaptichnium, and one of Isochirotherium. The presence of a fourth related ichnogenus, Brachychirotherium, cannot yet be confirmed in Britain. Emended diagnoses are proposed for all four ichnogenera; they may be readily distinguished by the shape of the hand (manus) and foot (pes) impression and especially by the phalangeal counts. The natural cast of a probable tail impression, associated with Chirotheriidae footprints from the British Triassic is figured for the first time, as is a rare detailed impression of skin and the tarsal region of an Isochirotherium lomasi pes cast.

Part 2 provides a critical history of the earliest discoveries of each of these ichnogenera in the British Triassic. It is subdivided into divisions, depending on the quality of data and existence of specimens, the localities in Britain which have yielded these ichnogenera; a detailed history and discussion is provided of the earliest discoveries made at each locality. The stratigraphic distribution and paleological significance of the ichnogenera/species are assessed.     

The Tetrapod Ichnogenus Protochirotherium Fichter and Kunz 2004, a Characteristic Early Triassic Morphotype of Central Pangea

Early Triassic chirotherian footprint assemblages from Poland, Germany, and Morocco are important for understanding archosaur evolution in the aftermath of the Permian-Triassic crisis. However, their ichnotaxonomy is confusing because various authors have interpreted their diversity differently. After an analysis and ichnotaxonomic re-assessment, the presence of the ichnogenera Brachychirotherium, Isochirotherium, and Chirotherium in these assemblages is not supported. Distant similarities with these ichnotaxa are functions of extra morphological variation and substrate-related factors. Instead, Early Triassic chirotherian footprints described under these names are assigned here to the ichnogenus Protochirotherium and to a more slender morphotype identified as Synaptichnium. In particular, Protochirotherium appears to be more widely distributed in central Pangea as a characteristic morphotype reflecting a distinct stage in archosaur evolution. Trackmakers were nonarchosaurian archosauriforms or, alternatively, stem-group crocodylians. Morphologically and temporally these footprints match the hypothetical ancestor of the Chirotherium barthii trackmaker. Chirotherium barthii appears by the beginning of the Middle Triassic. Because of its restricted stratigraphic range, and its wider distribution in central Pangea, Protochirotherium also has biostratigraphic significance for this region and can be considered as an indicator of Early Triassic-aged strata.     

Lavinipes Cheminii Ichnogen., Ichnosp. nov., A Possible Sauropodomorph Track from the Lower Jurassic of the Italian Alps

A new ichnotaxon is described from the Lower Jurassic (Upper Hettangian-Lower Sinemurian) carbonate tidal flats on the central-eastern Italian Alps. The narrow-gauge trackway is that of a large quadrupedal dinosaur. The pes is functionally tetradactyl with three rounded antero-medially directed digits, and the manus is pentadactyl. This quadrupedal form is close to Otozoum and Pseudotetrasauropus jaquesi both traditionally related to sauropodomorph trackmakers. The similarity with Otozoum is so marked that Lavinipes and Otozoum could be cogeneric. But the overall evidence today is that the Otozoum trackmaker was generally bipedal, whereas the trackmaker of L. cheminii is fully quadrupedal. The manual prints of L. cheminii show five short clawless digits and are different from the tetradactyl slender toed manual prints of Otozoum. The possible sauropodomorph affinity of the L. cheminii trackmaker is here discussed with an attempt to a revision of the Late Triassic-Jurassic tracks which have been traditionally related to sauropod and prosauropod.     

Jaw biomechanics in the South American aetosaur <Emphasis Type="Italic">Neoaetosauroides engaeus</Emphasis>

The function of the jaw apparatus and the possible dietary habits of the aetosaur Neoaetosauroides engaeus from the Triassic of South America were analyzed in comparison with Northern Hemisphere aetosaurs Desmatosuchus haplocerus and Stagonolepis robertsoni and the living short-snouted crocodile Alligator mississippiensis. The adductor and depressor jaw musculature of these was reconstructed on the basis of dental and skeletal comparisons with living closest relatives’ extant phylogenetic bracket (EPB), followed by the analysis of the moment arms of these muscles to infer feeding habits. The aetosaurian skull design indicates that the total leverage of the inferred jaw musculature provides force rather than speed. However, within aetosaurs, the high ratios of muscle moment arms to bite moments indicate stronger bites in the northern Hemisphere forms, and faster ones in Neoaetosauroides. These differences indicate more developed crushing, chopping, and slicing capacities, especially at the back of the tooth series for D. haplocerus and S. robertsoni; whereas it opens a window to consider different abilities in which speed is involved for N. engaeus. There are differences among aetosaurs in dental characteristics, position of the supratemporal fenestra, location of the jaw joint relative to the tooth row, and shape of the lower jaw. Neoaetosauroides does not show evidence of dental serrations and wear facets, probably consistent with a relatively soft and non-abrasive diet, for example soft leaves and/or larvae and insects without hard structures. It might be possible that Neoaetosauroides represents a tendency towards insectivorous feeding habits, exploiting a food source that was widespread in continental environments throughout the Triassic.     

The Mississippian Tetrapod Footprint Ichnogenus Palaeosauropus: Extramorphological Variation and Ichnotaxonomy

Palaeosauropus primaevus is a tetrapod footprint ichnotaxon first described from the Upper Mississippian (Visean) Mauch Chunk Formation near Pottsville, Pennsylvania, United States. Our relocation of the type locality and stratigraphic horizon of P. primaevus, a long-available but unstudied collection of tetrapod footprints from these strata, and our new collections allow a much fuller characterization of this ichnotaxon and the range of extramorphological variation encompassed by it. P. primaevus is characterized as the footprints of a quadruped with a pentadactyl pes and a tetradactyl manus, in which the pes frequently oversteps the manus and with which tail drags are common. In the manus, all digits are relatively broad and have rounded tips, digit III is longest, and digit IV is more widely separated from digit III than the other digits are from each other. The pes has five digits that are also wide and blunt-tipped, digit IV is longest, and digit V projects nearly laterally. P. primaevus is the track of a relatively large temnospondyl (～400 mm gleno-acetabular length) and documents the Mississippian presence of such large amphibians long before their body fossil record. Palaeosauropus also occurs in Mississippian strata in Indiana and is distinguished from the geologically younger but similar temnospondyl footprint ichnogenus Limnopus by its relatively narrower manus and pes that lack broad and rounded sole impressions.     

Triassic turtle tracks and the origin of turtles

Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisian) of Germany, and Chelonipus isp. from the late Early Triassic (Spathian) of Wyoming and Utah, are the oldest fossil evidence of turtles, but have been omitted in recent discussions of turtle origins. These tracks provide significant clues as to how early the turtle Bauplan originated. Turtle trackways are quite distinctive: the manus and pes form tracks nearly parallel to the midline and indicate an unusually wide gait in which the trackway width is nearly equal to the stride length. These tracks do not fit what would be expected to be made by Triassic Pappochelys or Odontochelys, a supposed prototurtle and an early turtle, respectively. In contrast, these tracks are consistent with what would be expected from the Triassic turtles Proganochelys and Palaeochersis. The features inferred to be present in Triassic turtle tracks support the notion that Odontochelys is a derived aquatic branch of the turtle stem lineage rather than the ancestral state of all turtles. Chelonipus also resembles the Permian track Pachypes dolomiticus, generally assigned to a pareiasaur trackmaker. These revelations highlight the need to consider all available evidence regarding turtle origins, rather than just the body fossils.     

Chirothere Footprint Sites from the Otter Sandstone Formation (Middle Triassic,late Anisian) of Devon,United Kingdom

Three chirothere footprint sites are documented from the Middle Triassic (Anisian) fluvial Otter Sandstone Formation of Sidmouth, Devon, UK. One site, on the foreshore below Peak Hill, has revealed numerous tracks, including a probable manus imprint, which are recorded here. Another site, also beneath Peak Hill, has produced a single probable manus track from a higher horizon. The third site, on the foreshore below Salcombe Hill Cliff, has yielded a small number of pes tracks similar to those from Peak Hill. The footprints at all sites are interpreted as belonging to a large Chirotherium ichnospecies, perhaps C. barthii Kaup. Unusually, the tracks are preserved in mudstone, often in convex epirelief, and are inferred to have been generated subaqueously. The apparent restriction of the footprints to the higher part of the Otter Sandstone Formation supports other evidence, such as a greater abundance of vertebrate skeletal material, subhorizontal rather than vertical rhizocretions, and a greater frequency of lacustrine facies, for a less arid climate and higher water table than lower in the sequence.     

Thinopus and a Critical Review of Devonian Tetrapod Footprints

Devonian tetrapod tracks and trackways can be recognized by three criteria: morphology of the manus and pes impressions that matches known Devonian tetrapod skeletal morphology, manus smaller than pes, and the alternating trackway pattern that results from lateral sequence walking in quadrupedal tetrapod locomotion. The first reported Devonian tetrapod track, named Thinopus antiquus, from Pennsylvania, is not a tetrapod track and is likely an impression of a fish coprolite(s). A critical review of the published Devonian track record indicates only three can be verified as produced by a tetrapod trackmaker—Genoa River, Australia; Easter Ross, Scotland; and Valentia Island, Ireland. The supposed tetrapod tracks from the Middle Devonian of the Zache?mie quarry, Poland, fail the criteria for identification as Devonian tetrapod tracks. Indeed, no convincing case has been made that the Zache?mie structures are tetrapod tracks. Instead, they are reinterpreted as fish nests/feeding traces (ichnogenus Piscichnus). The oldest Devonian tetrapod trackway is Givetian and this is the oldest record of a tetrapod, but the sparse record of Devonian tetrapod tracks is of no other biostratigraphic and little paleobiogeographic significance. Bona fide Devonian tetrapod tracks are from nonmarine facies, so they do not support a marginal marine origin of tetrapods. They indicate lateral sequence walking and pelvic-limb-propelled, fully terrestrial (subaerial) locomotion in freshwater environments by at least some Devonian tetrapods.     

Shape variability in tridactyl dinosaur footprints: the significance of size and function

The functional anatomy of the hindlimb of bipedal dinosaurs has been intensively studied. Yet, surprisingly little work has been done concerning functional adaptation of digits for terrestrial locomotion. While complete and articulated pes skeletons are scarce, pes shape is abundantly recorded by fossil footprints. We elucidate the significance of footprint shape and size for locomotion using a large sample (n = 303) of tridactyl dinosaur footprints from a broad range of geographical localities and time slots. Size and shape variation are characterized separately for theropods and ornithischians, the two principal trackmaker taxa. At smaller sizes, theropod footprints are best discriminated from ornithischian footprints by their smaller interdigital angle and larger projection of digit III; at larger sizes digital widths are effective discriminants. Ornithischian footprints increase in size from the Early Jurassic to the Late Cretaceous, a trend not observed in theropod footprints. Size and function are argued to be important determinants of footprint shape, and an attempt made to infer function from shape. Digit III projection and length-to-width ratio of the footprints are negatively correlated with size in both groups; digit impression width is positively correlated with size only in ornithischians. Digit III projection appears to be positively correlated with cursorial ability. Increased interdigital angles are associated with a decrease in digital width, possibly an adaptation for stability. Weak digit III projection and increased digital width are interpreted as adaptations for graviportality. Footprints yield great potential for the understanding of the functional morphology of dinosaur feet.     

Sauropod and Small Theropod Tracks from the Lower Jurassic Ziliujing Formation of Zigong City,Sichuan, China,with an Overview of Triassic–Jurassic Dinosaur Fossils and Footprints of the Sichuan Basin

A dinosaur footprint assemblage from the Lower Jurassic Ziliujing Formation of Zigong City, Sichuan, China, comprises about 300 tracks of small tridactyl theropods and large sauropods preserved as concave epireliefs (natural molds). The theropod footprints show similarities with both the ichnogenera Grallator and Jialingpus. Three different morphotypes are present, probably related to different substrate conditions and extramorphological variation. A peculiar preservational feature in a morphotype that reflects a gracile trackmaker with extremely slender digits, is the presence of a convex epirelief that occurs at the bottom of the concave digit impressions. It is possibly the result of sediment compaction underweight load when the pes penetrated the substrate, being a resistant residue during exhumation and weathering. The sauropod tracks belong to a trackway with eight imprints consisting of poorly preserved pes and manus tracks and a better preserved set, probably all undertracks. The narrow-gauge trackway pattern resembles the ichnogenus Parabrontopodus well known from the Jurassic but other features such as the minor heteropody are different. The assemblage enriches the dinosaur record from the famous Zigong locality and the evidence from the Lower Jurassic in this area that was restricted to a few skeletal remains and footprints. Furthermore it proves the presence of small theropods, whereas skeletons of the group, well- known from the Middle-Upper Jurassic of Zigong, are of medium to large size only. Remarkable is the dominance of saurischians in these assemblages, which is characteristic of Jurassic dinosaur communities whereas the Cretaceous record shows an increase of ornithopod groups. An overview of the dinosaur trace and body fossil record of the Sichuan Basin supports this view. The paleoenvironment can be designated as a low-latitude tropical freshwater lake as it is indicated by bivalve shells.     

Pterosaur Stance and Gait and the Interpretation of Trackways

The tracks ascribed to pterosaurs from the Late Jurassic limestones at Crayssac, France, must be pterosaurian because the manus prints are so far outside those of the pes, the pes print is four times longer than wide, and the manus prints appear to preserve distinct traces of a posteromedially directed wing-finger. These tracks are different in important ways from previously described Pteraichnus trackways, which have been variably considered pterosaurian, crocodilian, or indeterminate. No Pteraichnus (sensu stricto: those not from Crayssac) tracks have diagnostic features of pterosaurs and in none can a complete phalangeal or digital formula be reconstructed; however, all published Pteraichnidae tracks fulfill the criteria of poor preservation, and some have some diagnostic features of crocodile tracks. Reconstructions of pterosaurs walking in pteraichnid tracks do not fit those tracks well, but crocodiles do. In contrast, the Crayssac tracks demonstrate the erect stance and parasagittal gait previously reconstructed for pterosaurs. They also demonstrate that the footfall pattern was not as in typical reptiles (LH-RF-RH-LF), but that the manus must have been raised before the next forward step of the ipselateral foot (LH-LF-RH-RF), suggesting that the quadrupedal pattern was secondary. The metatarsus in pterosaurs was set low at the beginning of a stride, as it is in crocodilians and basal dinosaurs. The diagnosis of the Ichnofamily Pteraichnidae comprises features of possible crocodilian trackmakers, but not of possible pterosaurian trackmakers. Trackways considered for attribution to pterosaurs should show (1) manus prints up to three interpedal widths from midline of body, and always lateral to pes prints, (2) pes prints four times longer than wide at the metatarso-phalangeal joint, and (3) penultimate phalanges longest among those of the pes.     

An enigmatic early mesozoic dinosaur trackway from Zimbabwe

A trackway from Zimbabwe of probably the smallest dinosaur footprints recorded in Africa, is described and tentatively assigned to the Early Jurassic. The footprints are possibly those of a theropod and show strong negative (outward) rotation of the pes and are associated with manus prints. The shape of the footprints, unusual negative rotation, posterior curvature of digit IV and curious positioning of the manus prints in relation to the pes are enigmatic but somewhat reminiscent of Atreipus. Although a number of propositions are considered the most likely is that the animal was an immature dinosaur using a quadrupedal gait. A second trackway of slightly larger footprints of a bipedal theropod dinosaur is also recorded along with other diminutive tracks that suggest an early dinosaur assemblage, possibly dating from near the Trias‐sic‐Jurassic boundary.     

Grallator-Dominated Fossil Footprint Assemblages and Associated Enigmatic Footprints from the Chinle Group (Upper Triassic), Gateway Area,Colorado

The upper part of the Chinle Group (Late Triassic) of the Gateway area in western Colorado is extraordinarily rich in fossil footprint assemblages. Dominant track types include small Grallator tracks, generally attributed to Coelophysis-like theropods, which often occur in high densities of 50 to 100 per m². Other abundant ichnotaxa that are attributable to dinosaurs or dinosaur-like archosaurs include Pseudotetrasauropus and Tetrasauropus, attributed to prosauropods and sauropods, respectively. Several Pseudotetrasauropus-like tracks appear to be functionally didactyl and may indicate a new ichnotaxon that represents an animal that shows certain unusual features that are convergent with dromeosaurs and certain birds. Such convergence may reflect inherent growth programs as much as functional adaptations. Non-dinosaurian ichnotaxa include Brachychirotherium (probably of aetosaur affinity) and Rhynchosauroides, attributed to a sphenodontid/lizard-like form. Other ichnotaxa include probable therapsid (dicynodont) tracks labeled Pentasauropus sp., mammaloid (non-therian mammal and/or mammal-like reptile) tracks, and the trails of arthropods. Excellent preservation and high track densities mark the Gateway assemblages in a thin stratigraphic interval in the upper part of the Chinle Group (Rock Point Formation). The track assemblages are similar to those reported from the Chinle Group in other parts of the Colorado Plateau and Rocky Mountain region, extending over most of Colorado, Utah, northern Arizona and northern and eastern New Mexico. Some of the Chinle ichnotaxa (Grallator and Brachychirotherium) are found in the overlying Wingate Formation, indicating that it is also Late Triassic in age, at least in the lower part. However, overall the Chinle and Wingate assemblages are quite different, most notably in the rarity of mammaloid/mammal-like tracks in the Chinle Group.     

Trackways of the American Crocodile (Crocodylus acutus) in Northwestern Costa Rica: Implications for Crocodylian Ichnology

We documented trackways of free-living Crocodylus acutus on beaches at the mouths of Tamarindo and Ventanas estuaries, Costa Rica. Our crocodiles had estimated total lengths of 1–3 meters or more. Manus prints have five digits, with digits I–III bearing claw marks. Pes prints have four digits, with claw marks on digits I–III. The pes is plantigrade. Claws generally dig into the substrate. Apart from claw marks, digit I and the heel of the pes are usually the most deeply impressed parts of footprints. Trackways are wide-gauge. Pes prints are usually positioned just behind ipsilateral manus prints of the same set and may overlap them. Manus and pes prints angle slightly outward with respect to the crocodile's direction of movement. Claw-bearing digits of both the manus and pes may create curved, concave-toward-the-midline drag marks as the autopodium is protracted. The tail mark varies in depth and clarity, and in shape from nearly linear to markedly sinuous. Sometimes the tail mark hugs the trackway midline, but sometimes it is closer to, or even cuts across, prints of one side. American crocodile footprints and trackways are similar to those observed in other extant crocodylian species, indicating substantial trackway conservatism across the group.     

Sauropod Trackway Reflecting an Unusual Walking Pattern from the Early Cretaceous of Shandong Province,China

The trackway of a quadrupedal dinosaur from the Early Cretaceous (Albian) Qingquan tracksite (Tancheng, Shandong Province) is redescribed, and the trackmaker is identified as a sauropod. The trackway makes a slight turn towards the northwest and is characterized by an extremely narrow gauge pattern and an unusual configuration, i.e., a conspicuous difference between the position of the left and right manus tracks with respect to the position of the preceding pes track. Left manus tracks are located on the inside of the trackway, very close (and sometimes even in connection) to the opposite right pes tracks. So far, the Qingquan trackway is possibly the only extremely narrow-gauge sauropod trackway known from China. However, it is not clear to what extent this extremely narrow gauge pattern is related to the turning or a special behavior, or even linked to an injury (“limping trackway”). We tentatively attribute the Qingquan trackway to cf. Parabrontopodus, even though it has a rather low heteropody that is significantly lower than in Parabrontopodus and not typical for narrow-gauge sauropod trackways, but occurs in the wide-gauge ichnotaxon Brontopodus. Because of this discrepancy, the Qingquan trackway cannot readily be attributed to a more basal sauropod, which is generally considered the producer of narrow-gauge trackways. Therefore, the identification of a distinct sauropod group is not possible presently. The only skeletal remains of sauropods from the Lower Cretaceous of Shandong Province belong to the large titanosauriform, Euhelopus zdanskyi.     

Les pistes dinosauroïdes du Trias moyen français : interprétation et réévaluation de la nomenclature

Numerous dinosauroid footprints which showing sometimes manus imprint mark were gathered, since 1960, from the lower sandstones Triassic formations of the eastern border of the Massif Central (France). Tracks bearing levels are dated from palynological, micropalaeontological and palichnological data. They belong to the period upper Anisian-lower Ladinian. The paleontological results show bipedal digitigrade reptiles with erected, long hind limbs, having also pentadactyl mani and (II-IV) tridactyl feet. The osteological feet inferred structure is like that of Ceratosauria of Late Triassic age. The skeletons of first Dinosauria, diversified already well, are known in summit Ladinian and lower Carnien and those of their ancestors, Dinosauriformes, in Ladinian. And, for this reason, the aniso-ladinian dinosauroid footprints are ascribed to these last animals which thus appeared earlier, to Anisan even to late Olenekian. The chirotheroid hands show a “pseudosuchian” origin which possibly took place during the late Olenekian; feet modifications of these Crurotarsi being characterized by I and V digits reduction and a meso-tarsal joint. The Anisian-Ladinian dinosauroid footprints are ascribed to the ichnospecies Coelurosaurichnus perriauxi and Anchisauripus bibractensis. The discriminant analysis computed from these latter ichnospecies, and others from the German Triassic, French and USA Hettangian indicate that C. perriauxi and A. bibractensis can not be included into Grallator sensu Lull, 1953 or Coelurosaurichnus of Franconie. By this way, these taxa are well original and till now, there was no reason to change their nomenclature. Nevertheless because the numerous changes of Grallator which gathers now, most of dinosauroid footprints, it could be possible to include them into Grallator for the feet and into Atreipus when the manus trace is connected with the foot.     

Evidence for Prosauropod Dinosaur Gastroliths in the Bull Run Formation (Upper Triassic,Norian) of Virginia

Definitive criteria for distinguishing gastroliths from sedimentary clasts are lacking for many depositional settings, and many reported occurrences of gastroliths either cannot be verified or have been refuted. We discuss four occurrences of gastrolith-like stones (category 6 exoliths) not found within skeletal remains from the Upper Triassic Bull Run Formation of northern Virginia, USA. Despite their lack of obvious skeletal association, the most parsimonious explanation for several characteristics of these stones is their prolonged residence in the gastric mills of large animals. These characteristics include 1) typical gastrolith microscopic surface texture, 2) evidence of pervasive surface wear on many of these stones that has secondarily removed variable amounts of thick weathering rinds typically found on these stones, and 3) a width/length-ratio modal peak for these stones that is more strongly developed than in any population of fluvial or fanglomerate stones of any age found in this region. When taken together, these properties of the stones can be explained most parsimoniously by animal ingestion and gastric-mill abrasion. The size of these stones indicates the animals that swallowed them were large, and the best candidate is a prosauropod dinosaur, possibly an ancestor of the Early Jurassic gastrolith-producing prosauropod Massospondylus or Ammosaurus.

Skeletal evidence for Upper Triassic prosauropods is lacking in the Newark Supergroup basins; footprints (Agrestipus hottoni and Eubrontes isp.) from the Bull Run Formation in the Culpeper basin previously ascribed to prosauropods are now known to be underprints (Brachychirotherium parvum) of an aetosaur and underprints (Kayentapus minor) of a ceratosaur. The absence of prosauropod skeletal remains or footprints in all but the uppermost (upper Rhaetian) Triassic rocks of the Newark Supergroup is puzzling because prosauropod remains are abundant elsewhere in the world in Upper Triassic (Carnian, Norian, and lower Rhaetian) continental strata. The apparent scarcity of prosauropods in Upper Triassic strata of the Newark Supergroup is interpreted as an artifact of ecological partitioning, created by the habitat range and dietary preferences of phytosaurs and by the preservational biases at that time within the lithofacies of the Newark Supergroup basins.