Trackway Pattern Research Articles

Captorhinid trackways from mid- to late Permian red beds in Morocco: Implications for locomotion and the palaeobiogeography of northwest Gondwana

In this paper, we report a new vertebrate ichnoassemblage from the mid- to late Permian red beds of the Ikakern Formation (Tourbihine Member, T2) from the Argana Basin of Morocco, to improve knowledge of paleobiology and palaeobiogeography. The ichnofossils comprise than 50 footprints organized as four trackways and assigned to the ichnogenus Hyloidichnus. The tetrapod tracks are preserved in convex hyporelief and concave epirelief on upper and lower mud-rich surfaces near the top of fine-grained sandstone units. The trackway pattern and the alternating arrangement of the pes-manus sets suggest a sprawling and symmetrical gait, with the movements of the front and hind limbs being of similar size, and it is likely that the animal moved at slow trot. We infer that the potential trackmaker was a captorhinomorph within the Moradisaurinae. This new fossil discovery helps reconstruct the palaeoenvironments and the palaeogeographic distribution of these Permian organisms, with Morocco acting as a faunal exchange gateway between western Gondwana and western Laurasia. Besides the tetrapod tracks, the red beds contain ubiquitous rain-drop marks, current ripples, plant fossil impressions, invertebrate burrows, tetrapod skin imprints, and a single insect wing that suggest that the strata were deposited in an episodically inundated alluvial plain.

The early Mesozoic saurischian trackways Evazoum and Otozoum: implications for ‘prosauropod’ (basal sauropodomorph) gaits

ABSTRACT Trackways of bipeds and quadrupeds attributed to Late Triassic and Early Jurassic basal sauropodomorphs (‘prosauropods’) fall into several ichnogenera. Four of these – Otozoum, Pseudotetrasauropus, Evazoum and Kalosauropus – are conceptually subsumed into the OPEK plexus, where the former two represent large facultative quadrupeds, and the latter two represent bipeds. In revaluating ~53 measurable Evazoum tracks from 13 Upper Triassic sites in the Northern Hemisphere, we found a consistently enlarged proximal pad on digit II, which together with digit I show highly variable registration. These suggest that the trackmakers tended to preferentially carry weight on digits III and IV. Furthermore, over a dozen Evazoum trackways also indicate notable variations in trackway width, consistent with previous inferences about the ‘prosauropodian’ gait. Comparisons to five Kalosauropus trackways from the Lower Jurassic of the Southern Hemisphere show that these two more closely related track types were likely made by basal sauropodomorphs (prosauropods) that were more fully adapted to obligatory bipedalism. The much larger Otozoum, reported from 16 trackways globally from both the Upper Triassic and Lower Jurassic, has trackway patterns that indicate changes in trackway width and shifts between bipedal and quadrupedal progression.

Estimating Gaits of an Ancient Crocodile-Line Archosaur Through Trajectory Optimization, With Comparison to Fossil Trackways.

Fossil trackways provide a glimpse into the behavior of extinct animals. However, while providing information of the trackmaker size, stride, and even speed, the actual gait of the organism can be ambiguous. This is especially true of quadrupedal animals, where disparate gaits can have similar trackway patterns. Here, predictive simulation using trajectory optimization can help distinguish gaits used by trackmakers. First, we demonstrated that a planar, five-link quadrupedal biomechanical model can generate the qualitative trackway patterns made by domestic dogs, although a systematic error emerges in the track phase (relative distance between ipsilateral pes and manus prints). Next, we used trackway dimensions as inputs to a model of Batrachotomus kupferzellensis, a long-limbed, crocodile-line archosaur (clade Pseudosuchia) from the Middle Triassic of Germany. We found energetically optimal gaits and compared their predicted track phases to those of fossil trackways of Isochirotherium and Brachychirotherium. The optimal results agree with trackways at slow speeds but differ at faster speeds. However, all simulations point to a gait transition around a non-dimensional speed of 0.4 and another at 1.0. The trackways likewise exhibit stark differences in the track phase at these speeds. In all cases, including when simulations are constrained to the fossil track phase, the optimal simulations after the first gait transition do not correspond to a trot, as often used by living crocodiles. Instead, they are a diagonal sequence gait similar to the slow tölt of Icelandic horses. This is the first evidence that extinct pseudosuchians may have exhibited different gaits than their modern relatives and of a gait transition in an extinct pseudosuchian. The results of this analysis highlight areas where the models can be improved to generate more reliable predictions for fossil data while also showcasing how simple models can generate insights about the behavior of extinct animals.

Saurischian dinosaur tracks from the Upper Triassic of southern Queensland: possible evidence for Australia’s earliest sauropodomorph trackmaker

ABSTRACT Fossil footprints provide the only evidence of Triassic-aged dinosaurs in Australia. While historically several Triassic dinosaur tracksites are reported, only one specimen exists for direct study. Evidence for the Rhondda colliery (Ipswich) trackmaker, Upper Triassic Blackstone Formation as a very large-bodied Triassic predatory dinosaur is not supported by the present study because of overestimated footprint length measurements, and we question earlier interpretations that these tracks are Eubrontes-like. Instead, we recognise shared characteristics with the sauropodomorph ichnogenus Evazoum. The track morphology resembles that of Evazoum on account of the distinct shape and position of the impression of the metatarsophalangeal pad for digit IV. The mesaxony of the Blackstone Formation track is also low, but possibly slightly higher than in Evazoum, if the proportions of the digital impressions are correctly interpreted. Finally, the trackway pattern shows constant track inward rotation, a feature observed in typical Evazoum and mostly absent in Eubrontes. Therefore, we assign these Australian tracks as Evazoum ichnosp. indet. If our assessment of the Blackstone Formation tracks is correct, they provide the first and only evidence of basal sauropodomorph dinosaurs from Australia. In addition to this record, we give an overview of other reported (but lost) Australian Triassic dinosaur footprints.

Tracking the Origin and Early Evolution of Reptiles

The origin of Reptilia and the biostratigraphic and palaeobiogeographic distribution of its early representatives are still poorly understood. An independent source of information may come from the extensive Carboniferous footprint record of reptiles, which is arguably richer and more complete than the skeletal record. Nevertheless, previous studies often failed to provide useful information because they were based on poorly preserved material and/or characters non-exclusive of reptile tracks. In fact, a large part of the supposed early reptile tracks can be assigned to the anamniote ichnotaxon Hylopus hardingi. Here, we revise the ichnotaxon Hylopus hardingi based on anatomy-consistent material, attribute it to anamniote reptiliomorphs, and distinguish it from Notalacerta missouriensis, the earliest ichnotaxon that can be attributed to reptiles, and the somewhat younger Varanopus microdactylus (attributed to parareptiles, such as bolosaurians) and Dromopus lacertoides (attributed to araeoscelid reptiles and non-varanodontine varanopids). These attributions are based on correlating morphofunctional features of tracks and skeletons. Multivariate analysis of trackway parameters indicates that the late Bashkirian Notalacerta missouriensis and Hylopus hardingi differ markedly in their trackway patterns from Late Mississippian Hylopus hardingi and Late Pennsylvanian reptile tracks, which appear to share a derived amniote-like type of gait. While the first occurrence/appearance of reptile tracks in the tetrapod footprint record during the late Bashkirian corresponds to the first occurrence/appearance of reptiles in the skeletal record, footprints significantly enlarge the paleobiogeographic distribution of the group, suggesting an earlier radiation of reptiles during the Bashkirian throughout North America and possibly North Africa. Dromopus appeared in the Kasimovian together with the diapsid group Araeoscelidia, but footprints from Western-European occurrences enlarge the paleobiogeographic distribution of diapsids and varanopids. Varanopus and bolosaurian parareptiles appear in the Gzhelian of North America. Older parareptiles are, however, known from the late Moscovian. In all, the footprint record of early reptiles supplements the skeletal record, suggesting possible future lines of research.

Unusual dinosaur trackway preservation as clues to paleo-landscape and behavior from the Lower Cretaceous Luohe Formation, Shaanxi Province, China

Poorly preserved tracks have limited ichnotaxonomic or biotaxon utility, but may reveal useful information about the paleoenvironment, behavior and track taphonomy. Eight mostly parallel to sub parallel trackway segments (T1–T8) were registered on a truncation surface in the Lower Cretaceous Luohe Formation of Shaanxi Province. These attest to the passage of several bipeds, probably all theropods, in a paleo-contour-parallel, south-north direction in an arid setting. Quality of preservation in these trackways is poor, but notably superior in two additional trackways (T9–T10) on a foreset surface. Trackway T9 indicates a didactyl trackmaker, probably a deinonychosaurian, heading north to south. This is the 13th report of deinonychosaurian tracks from the Lower Cretaceous of China. If any or all the eight south-north oriented trackway segments represent continuations of other segments in the same trackways, the total number of individual trackmakers heading in this direction may have been as low as three. Although the trackway pattern and sedimentological evidence could indicate a physically controlled pathway influencing the direction taken by these trackmakers, the possibility that the trackways also represented small social or gregarious group cannot be ruled out.

Variation in sauropod trackway pattern from the Tuchengzi Formation (Jurassic-Cretaceous boundary) in western Liaoning, China

Sauropod tracks, particularly those attributable to the ichnogenus Brontopodus are becoming increasingly well known in the Jurassic and Cretaceous of China. Globally there are indications that wide gauge forms, attributable to titanosauriform sauropods increase in the Cretaceous. However, differentiating wide and narrow gauge, broadly categorized as large manus (low heteropody) Brontopodus or small manus (high heteropody) Parabrontopodus, respectively is complicated by the occurrence of intermediate forms with medium gauge and intermediate heteropody, and the unknown role played by size variation. We here describe two morphotypes from the Jurassic-Cretaceous boundary sequences of the Tuchengzi Formation of western Liaoning that are medium sized and mainly distinguished by striking variations in manus rotation angles. Currently Brontopodus birdi from the Lower Cretaceous of North America is typified by wide gauge and low manus rotation (~10°), whereas Brontopodus pentadactylus from the Lower Cretaceous of Korea is characterized by high outward rotation (~90°). We consider such large differences in footprint rotation could be useful in distinguishing morphotypes and diagnostic gaits in sauropod ichnology as they have proven to be in the case of some other dinosaurs. The trackways from the Tuchengzi Formation and their peculiar patterns are a useful basis and starting point for future discussions on the ichnotaxonomy of sauropod trackways.

Tracking the Pliensbachian–Toarcian Karoo firewalkers: Trackways of quadruped and biped dinosaurs and mammaliaforms

The Karoo igneous rocks represent one of the largest continental flood basalt events (by volume) on Earth, and are not normally associated with fossils remains. However, these Pliensbachian–Toarcian lava flows contain sandstone interbeds that are particularly common in the lower part of the volcanic succession and are occasionally fossiliferous. On a sandstone interbed in the northern main Karoo Basin, we discovered twenty-five tridactyl and tetradactyl vertebrate tracks comprising five trackways. The tracks are preserved among desiccation cracks and low-amplitude, asymmetrical ripple marks, implying deposition in low energy, shallow, ephemeral water currents. Based on footprint lengths of 2–14 cm and trackway patterns, the trackmakers were both bipedal and quadrupedal animals of assorted sizes with walking and running gaits. We describe the larger tridactyl tracks as “grallatorid” and attribute them to bipedal theropod dinosaurs, like Coelophysis, a genus common in the Early Jurassic of southern Africa. The smallest tracks are tentatively interpreted as Brasilichnium-like tracks, which are linked to synapsid trackmakers, a common attribution of similar tracks from the Lower to Middle Jurassic record of southern and southwestern Gondwana. The trackway of an intermediate-sized quadruped reveals strong similarities in morphometric parameters to a post-Karoo Zimbabwean trackway from Chewore. These trackways are classified here as a new ichnogenus attributable to small ornithischian dinosaurs as yet without a body fossil record in southern Africa. These tracks not only suggest that dinosaurs and therapsids survived the onset of the Drakensberg volcanism, but also that theropods, ornithischians and synapsids were among the last vertebrates that inhabited the main Karoo Basin some 183 Ma ago. Although these vertebrates survived the first Karoo volcanic eruptions, their rapidly dwindling habitat was turned into a land of fire as it was covered by the outpouring lavas during one of the most dramatic geological episodes in southern Africa.

Upper Jurassic dinosaur tracks from the Tianchihe Formation of Shanxi Province, China: review and new observations

ABSTRACT A sauropod track assemblage from a surface in the Upper Jurassic fluvial Tianchihe Formation at the Guanxi site, Shanxi Province, China, is re-documented and analysed in detail, together with a recently discovered new locality situated nearby. In contrast to earlier reports, the former includes four trackways plus isolated tracks (41 tracks in total) instead of five trackways (37 tracks in total) identified earlier, with pes prints reaching more than 60 cm in length. The new site has three pes-manus track pairs belonging to smaller individuals, with pes prints being about 20 cm in length. The absence of larger sized tracks at this locality suggests the possible presence of size-differentiated groups representing juveniles or subadults. Track morphology, heteropody and the medium-wide gauge trackway pattern at both sites support an assignment to the ichnogenus Brontopodus. Trackmakers were eusauropods, possibly mamenchisaurids or more advanced forms such as macronarians. Results of re-investigation allow a new interpretation of trackway orientations and trackmaker behaviour, respectively, as well as a calculation of progression speeds that suggest walking movement.

An anatomy-consistent study of the Lopingian eolian tracks of Germany and Scotland reveals the first evidence of the end-Guadalupian mass extinction at low paleolatitudes of Pangea

The poor preservation and apparent monospecifity of Permian tetrapod footprints from eolian paleoenvironments have thus far hampered their reliable interpretation. This study clarifies how this is due to distinct and repeated ichnotaphonomic effects on trackway pattern and footprint morphology on originally inclined planes. Once these effects are excluded, the anatomy-consistent ichnotaxobases useful for ichnotaxonomy can be recognized. Several nomina dubia are identified, among these the ichnogenus Chelichnus, here considered a taphotaxon. The eolian ichnoassociations from the Lopingian of Scotland and Germany include six different ichnotaxa: cf. Capitosauroides isp. (?eutheriodont therapsid), Dicynodontipus geinitzi (cynodont therapsid), Dolomitipes isp. (dicynodont therapsid), Pachypes loxodactylus n. comb. (pareiasaurian parareptile), Procolophonichnium isp. (small parareptile) and Rhynchosauroides isp. (non-archosauriform neodiapsid). This is completely different from the interpretations of the last 20 years, which postulated that these paleoenvironments comprised monospecific associations of synapsid tracks. These ichnoassociations are instead moderately diverse, similar to low-latitude marginal marine to floodplain ichnoassociations and belong to the Lopingian Paradoxichnium footprint biochron. The Cornberg Formation of Germany, being constrained between the Illawarra reversal and the mid-Wuchiapingian Kupferschiefer at the Rotliegend/Zechstein transition, constitutes the earliest evidence of Lopingian tetrapod faunas at low paleolatitudes and the first evidence of low-paleolatitude faunal turnover related to the end-Guadalupian mass extinction from both the skeleton and the track record. This suggests a global extension of the dinocephalian extinction event, which occurred at high-mid (South Africa and Russia) and low (Western Europe) paleolatitudes of Pangea about 259–260 Ma and was probably triggered by the eruption of the Emeishan Large Igneous Province of SW China, which considerably changed global environmental conditions in both marine and continental settings.

Middle Triassic Pentasauropus-dominated ichnofauna from western Gondwana: Ichnotaxonomy, palaeoenvironment, biostratigraphy and palaeobiogeography

Quadruped trackways of large pentadactyl footprints are reported from the Middle Triassic (Anisian-Ladinian) Cerro de las Cabras Formation of the Cuyo Basin, Mendoza Province, central-western Argentina. The track-bearing strata are interpreted as deposited by sheetfloods in a mixed flat where water was ponded in a playa-lake setting. The vertebrate trackways are assigned to the ichnogenus Pentasauropus, originally described from the Upper Triassic Elliot Formation of South Africa, based on the presence of five equally spaced digit imprints that form an anteriorly convex broad arcuate pattern. A new ichnospecies, Pentasauropus argentinae nov. isp., is erected for the Argentinian material because of the distinct heteropody, inward rotation of the pes and outward rotation of the manus imprints, and the presence of palm/sole traces, and the diagnosis of the ichnogenus is emended. Pes/manus set arrangement and trackway patterns indicate a sprawling limbed trackmaker with an abducted posture for the fore-limbs and at least a semi-abducted posture for the hindlimbs, which suggests that the trackmaker was a kannemeyeriiform dicynodont. Associated archosaur ichnotaxa (Chirotherium barthii, Chirotherium cf. C. rex, Isochirotherium cf. I. coureli) point to a Middle Triassic age for the trackway-bearing strata in agreement with bracketing geochronological data. The rare occurrence of the therapsid footprint Dicynodontipus isp. is also compatible with the inferred age. The moderate abundance and oldest occurrence of Pentasauropus from three areas in Argentina suggest an origin for this ichnogenus in southwestern Gondwana, and presumably this area was a faunal exchange gate between southeastern and southwestern Gondwana and south Gondwana and North America.

Different trackway patterns in titanosaur sauropods: Analysis of new Titanopodus tracks from the Upper Cretaceous of Mendoza, Neuquén Basin, Argentina

The discovery of new Titanopodus trackways (Loncoche Formation, Argentina) shed light on the locomotion of titanosaur sauropods. Two patterns related with different size of trackmakers are identified based on ichnological and anatomical evidences. AC-1 and AC-4 trackways (pattern 1) are characterized by alternated manus and pes tracks. This is congruent with an asynchronous gait produced by large individuals that walked at 4.7–4.8 km/h. AC-3 trackway (pattern 2) shows some elongated and distorted tracks interpreted as overlapped manus and pes prints. This interpretation is supported by the presence of clear juxtaposed or partially overlapped manus and pes prints in some parts of the trackway. Pattern 2 is preliminary assigned to an amble gait produced by a smaller individual that walked at 3.7 km/h. These two patterns can be analyzed as different gaits in titanosaurs that walked together.

First report of sauropod tracks from the Upper Jurassic Tianchihe Formation of Guxian County, Shanxi Province, China

This paper presents the first report of sauropod tracks from the Upper Jurassic of Shanxi Province, China. Dinosaur tracks appear concentrated in five trackways, in different stratigraphic levels of the Late Jurassic Tianchihe Formation. Tracks are dominantly small and medium-size sauropod tracks and are tentatively assigned to Brontopodus based on preserved track morphology, trackway pattern and statistical analysis. The Tianchihe Formation in which the tracks appear shows a gradual change from meandering fluvial to sandy braided fluvial depositional systems developed in a seasonally arid environment. Comparisons of the evaluated speed of bipedal to quadruped trackways indicate that the slower walk more easily produces pes-dominated overprints. Trackways in the Guxian tracksite appear following different orientations, suggesting that these trackways were produced by different sauropods at different times. An unusual trackway following a curved pattern has been identified in the site and could represent a special locomotion character or a social behavior. The presence of eolian deposits in central Shanxi Province could have acted as a paleogeographic and paleoenvironmental barrier for the dispersion of the Yanliao Biota that survived in northern Hebei-western Liaoning and northestern Shanxi Province to the Ordos Basin during the Late Jurassic.

Geometric morphometric analysis of intratrackway variability: a case study on theropod and ornithopod dinosaur trackways from Münchehagen (Lower Cretaceous, Germany).

A profound understanding of the influence of trackmaker anatomy, foot movements and substrate properties is crucial for any interpretation of fossil tracks. In this case study we analyze variability of footprint shape within one large theropod (T3), one medium-sized theropod (T2) and one ornithopod (I1) trackway from the Lower Cretaceous of Münchehagen (Lower Saxony, Germany) in order to determine the informativeness of individual features and measurements for ichnotaxonomy, trackmaker identification, and the discrimination between left and right footprints. Landmark analysis is employed based on interpretative outline drawings derived from photogrammetric data, allowing for the location of variability within the footprint and the assessment of covariation of separate footprint parts. Objective methods to define the margins of a footprint are tested and shown to be sufficiently accurate to reproduce the most important results. The lateral hypex and the heel are the most variable regions in the two theropod trackways. As indicated by principal component analysis, a posterior shift of the lateral hypex is correlated with an anterior shift of the margin of the heel. This pattern is less pronounced in the ornithopod trackway, indicating that variation patterns can differ in separate trackways. In all trackways, hypices vary independently from each other, suggesting that their relative position a questionable feature for ichnotaxonomic purposes. Most criteria commonly employed to differentiate between left and right footprints assigned to theropods are found to be reasonably reliable. The described ornithopod footprints are asymmetrical, again allowing for a left–right differentiation. Strikingly, 12 out of 19 measured footprints of the T2 trackway are stepped over the trackway midline, rendering the trackway pattern a misleading left–right criterion for this trackway. Traditional measurements were unable to differentiate between the theropod and the ornithopod trackways. Geometric morphometric analysis reveals potential for improvement of existing discriminant methods.

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 Zachełmie quarry, Poland, fail the criteria for identification as Devonian tetrapod tracks. Indeed, no convincing case has been made that the Zachełmie 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.

First Report of Small Ornithopodichnus Trackways from the Lower Cretaceous of Sichuan, China

Trackways of ornithopods are well-known from the Lower Cretaceous of East Asia, particularly in Korea and China. However, most morphotypes have been identified as Caririchnium which is characterized by moderate mesaxony, the ratio length = width, or length > width and, in some cases, by a quadrupedal gait. In 2009 the ichnogenus Ornithopodichnus, which exhibits distinctively weak mesaxony and a broader, transverse pes imprint with the ratio length < width, was identified in Korea, on the basis of material with suboptimal preservation. The trackmaker was a large ornithopod. Subsequently, in 2009 a second report recognized Ornithopodichnus in China, the trackmaker being a moderately large quadruped. In 2012, Ornithopodichnus was described on the basis of well-preserved material from the Upper Cretaceous of Korea, in this case left by a small, gregarious biped. Herein we document, a fourth occurrence of Ornithopodichnus in the Lower Cretaceous Feitianshan Formation of Sichuan, China which is a further example of trackways that can be attributed to small, bipedal and gregarious ornithopods. Morphology, size, trackway pattern and speed of locomotion correspond well with trackways known from the Korean Hwasun tracksite. Possibly, the occurrence of Ornithopodichnus which is restricted to East Asia thus far, is related to ecological and biogeographical pecularities in this area.

Upper Cretaceous dinosaur track assemblages and a new theropod ichnotaxon from Anhui Province, eastern China

Several noteworthy Cretaceous tracksites are known in the Huizhou District (Huangshan City) in the Yangtzee valley of southern Anhui Province. These include some that have been known since the late 1970s but have not been studied in detail until now. The footprints described here occur in siliciclastic fluvial deposits in three distinct horizons. The Xiaohutian tracksite in the Upper Cretaceous Xiaoyan Formation is the most interesting, being situated at a historically famous location used as a Taoist and Buddhist shrine. The Xiaohutian tracksite yields an assemblage with three different morphotypes of non-avian theropod tracks including the new ichnotaxon Paracorpulentapus zhangsanfengi that can be attributed to a theropod with relatively short “fleshy” toes showing convergence with the footprints of small ornithopods. A further diagnostic feature is the trackway pattern with relatively short steps. Associated ichnofossils are invertebrate traces that can be assigned to eurybathic forms such as Palaeophycus and ?Planolites or ?Scoyenia. Thus far skeletal remains from the Xiaoyan Formation have proved the pachycephalosaur Wannanosaurus and indeterminate sauropods. The ichnoassemblages enlarge the known dinosaur fauna by small- to medium-sized theropods that are identified here as the trackmakers and that are otherwise rare in Upper Cretaceous deposits of eastern China. The Shangshangen locality is another significant tracksite which has yielded small bird tracks (cf. Koreanaornis) in association with small tracks of non-avian theropods.

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.

Chirotherium Trackways from the Middle Triassic of Guizhou, China

Triassic tetrapod footprints from China are less well known than those from the Jurassic and Cretaceous. Archosaurian trackways of the ichnogenus Chirotherium were found in the Middle Triassic Guanling Formation in Zhenfeng County (Guizhou Province) at the southwestern edge of the Yangtze plate in the early 1960s but were not correctly identified and adequately described until 40 years later. Here we give a detailed re-description and review of the trackways, which are known from two localities near the villages of Niuchang and Longchang. They occur on the bedding surface of a mud-cracked argillaceous dolostone deposited in a near-shore, shallow-water environment. Their morphology and general trackway pattern indicate that they pertain to the ichnospecies Chirotherium barthii, well known from Middle Triassic track surfaces of Europe, North and South America, and northern Africa. A peculiarity of the trackways from China are the low pace angulation and stride length, reflecting slow-moving trackmakers, which were basal crown-group archosaurs, possibly early representatives of the dinosaur-bird line or, alternatively, stem-group crocodylians. These tracks constitute the only chirotheriid record known from Asia thus far and indicate a Pangea-wide distribution for this ichnotaxon. Biostratigraphically, assemblages with C. barthii are characteristic of the early Anisian, an age assignment already supported for the Guanling Formation based on conodont and bivalve biostratigraphy. In contrast, however, radiometric data from an interlayered ash bed indicate a Ladinian age.

VINEGAROON (ARACHNIDA: THELYPHONIDA: THELYPHONIDAE) TRACKWAY PRODUCTION AND MORPHOLOGY: IMPLICATIONS FOR MEDIA AND MOISTURE CONTROL ON TRACKWAY MORPHOLOGY AND A PROPOSAL FOR A NOVEL SYSTEM OF INTERPRETING ARTHROPOD TRACE FOSSILS

ABSTRACT Neoichnological experiments with vinegaroons (Arachnida: Thelyphonida: Thelyphonidae) were conducted to describe the trackway patterns, evaluate the preservation quality and potential of its trackways in different sediment textures and moisture conditions, and compare them to trackways found in the fossil record. Trackways were produced in nine experimentally controlled variations of sediment size (fine-, medium-, or coarse-grained sand) and moisture added to the sediment surface (0 mL, 5 mL, or 10 mL). Trackways were photographed and video recorded during trackway production, and cast in plaster. Individual tracks were oblong to linear, with the first and third foot on each side producing a track parallel to the direction of motion, and the second foot producing a track perpendicular to the direction of motion. Video evidence indicates that track associations form a triangular pattern with the track of the second foot furthest from the midline of the trackway, rather than a linear pattern as des...