Deinonychosaur trackways in southeastern China record a possible giant troodontid.

The Longxiang tracksite (lower Upper Cretaceous, Shanghang Basin) includes twelve didactyl deinonychosaur tracks that fall into two morphologies, differentiated by both size and form. The smaller tracks (∼11 cm long) are referable to the ichnogenus Velociraptorichnus. The larger tracks (∼36 cm long) establish the ichnotaxon Fujianipus yingliangi. Based on the size of the tracks, F. yingliangi has an estimated hip height of over 1.8 m, a size comparable to that of the largest known deinonychosaurs, i.e., Austroraptor and Utahraptor. The reduced form of digit IV, relative to digit III, indicates that F. yingliangi is a probable troodontid. Gigantism evidently evolved independently at least four times within the Deinonychosauria and within at least three major lineages: the Eudromaeosauria, Unenlagiidae, and Troodontidae. In the mid-Cretaceous of Asia, the evolution of F. yingliangi overlapped with that of early large-bodied tyrannosauroids and with previously established large allosaurids (although the latter may have been in decline).

Basal sauropodomorph locomotion: ichnological lessons from the Late Triassic trackways of bipeds and quadrupeds (Elliot Formation, main Karoo Basin).

Using modern ichnological and stratigraphic tools, we reinvestigate two iconic sauropodomorph-attributed tetradactyl ichnogenera, Pseudotetrasauropus and Tetrasauropus, and their stratigraphic occurrences in the middle Upper Triassic of Lesotho. These tracks have been reaffirmed and are stratigraphically well-constrained to the lower Elliot Formation (Stormberg Group, Karoo Basin) with a maximum depositional age range of <219-209 Ma (Norian). This represents the earliest record of basal sauropodomorph trackways in Gondwana, if not globally. Track and trackway morphology, the sedimentary context of the tracks, and unique features (e.g., drag traces) have enabled us to discuss the likely limb postures and gaits of the trackmakers. Pseudotetrasauropus has bipedal (P. bipedoida) and quadrupedal (P. jaquesi) trackway states, with the oldest quadrupedal Pseudotetrasauropus track and trackway parameters suggestive of a columnar, graviportal limb posture in the trackmaker. Moreover, an irregularity in the intermanus distance and manus orientation and morphology, in combination with drag traces, is indicative of a non-uniform locomotory suite or facultative quadrupedality. Contrastingly, Tetrasauropus, the youngest trackway, has distinctive medially deflected, robust pedal and manual claw traces and a wide and uniform intermanus distance relative to the interpedal. These traits suggest a quadrupedal trackmaker with clawed and fleshy feet and forelimbs held in a wide, flexed posture. Altogether, these trackways pinpoint the start of the southern African ichnological record of basal sauropodomorphs with bipedal and quadrupedal locomotory habits to, at least, c. 215 Ma in the middle Late Triassic.

Lower cretaceous avian-dominated, theropod, thyreophoran, pterosaur and turtle track assemblages from the Tugulu Group, Xinjiang, China: ichnotaxonomy and palaeoecology.

Rich tetrapod ichnofaunas, known for more than a decade, from the Huangyangquan Reservoir (Wuerhe District, Karamay City, Xinjiang) have been an abundant source of some of the largest Lower Cretaceous track collections from China. They originate from inland lacustrine clastic exposures of the 581-877 m thick Tugulu Group, variously divided into four formations and subgroups in the northwestern margin of the Junggar Basin. The large Huangyangquan track assemblages occur in the Lower layer/Subgroup II. Similarly-composed track assemblages also occur at the smaller Asphaltite site in the Upper Layer/Subgroup III. The Huangyangquan assemblages have yielded more than 1,500 identified tracks including abundant tracks of avian and non-avian theropods, pterosaurs and turtles and less abundant tracks of stegosaurs. Previous avian track identifications have been reassessed to conclude that Moguiornipes robustus is a taphotaxon and Koreanaornis dodsoni might be better accommodated in the ichnogenus Aquatilavipes which appears to be the dominant avian ichnotaxon. The avian track Ignotornis is also recognized and represents the first occurrence of this ichnogenus in China. Although the Huangyangquan assemblages lack some of the larger components (e.g., sauropodan and ornithopodan tracks) known from other Lower Cretaceous localities, the association of abundant tracks of smaller tetrapods (avian and non-avian theropods, pterosaurs and turtles) appears to be representative of lacustrine basin faunas of this region, and are an excellent example of the shorebird ichnocoenosis/ichnofacies concept. This is the first comprehensive review and re-analysis of an important Lower Cretaceous ecosystem.

Trackway evidence for large bipedal crocodylomorphs from the Cretaceous of Korea.

Large well-preserved crocodylomorph tracks from the Lower Cretaceous (? Aptian) Jinju Formation of South Korea, represent the well-known crocodylomorph ichnogenus Batrachopus. The Korean sample includes multiple, narrow-gauge, pes-only trackways with footprint lengths (FL) 18-24 cm, indicating trackmaker body lengths up to ~3.0 m. Surprisingly, the consistent absence of manus tracks in trackways, with well-preserved digital pad and skin traces, argues for bipedal trackmakers, here assigned to Batrachopus grandis ichnosp. nov. No definitive evidence, either from pes-on-manus overprinting or poor track preservation, suggests the trackways where made by quadrupeds that only appear bipedal. This interpretation helps solve previous confusion over interpretation of enigmatic tracks of bipeds from younger (? Albian) Haman Formation sites by showing they are not pterosaurian as previously inferred. Rather, they support the strong consensus that pterosaurs were obligate quadrupeds, not bipeds. Lower Jurassic Batrachopus with foot lengths (FL) in the 2-8 cm range, and Cretaceous Crocodylopodus (FL up to ~9.0 cm) known only from Korea and Spain registered narrow gauge trackways indicating semi-terrestrial/terrestrial quadrupedal gaits. Both ichnogenera, from ichnofamily Batrachopodidae, have been attributed to Protosuchus-like semi-terrestrial crocodylomorphs. The occurrence of bipedal B. grandis ichnosp. nov. is evidence of such adaptations in the Korean Cretaceous.

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.

Largest Cretaceous lizard track assemblage, new morphotypes and longest trackways comprise diverse components of an exceptional Korean Konservat-Lagerstätten ichnofauna.

A newly discovered assemblage of lizard tracks from the Lower Cretaceous Jinju Formation (Sindong Group, Gyeongsang Basin) Korea is the largest yet reported from the Cretaceous. It consists of at least 95 tracks comprising five trackways, including a meter-long trackway (T1) with 50 footprints assigned to the new ichnotaxon Neosauroides innovatus ichnosp. nov. Two other trackways (T2 and T3) are designated N. innovatus paratypes characterized by strong heteropody, relatively wide trackways and small narrow manus tracks. These morphological characteristics distinguish Neosauroides innovatus from the previously reported lizard trackways Sauripes hadongensis from the Hasandong Formation and Neosauroides koreaensis from the Haman Formation, both also from the Gyeongsang Basin. These three lizard track assemblages from the Korean Cretaceous constitute the entire global lizard track record for this period. The Mesozoic record of lizard tracksites is more localized than the lizard body fossil record. This limited distribution suggests bias in the track record and the fossil record more generally. However, due to deposition of fine-grained substrates, suitable for high definition track registration, the Jinju Formation is increasingly well known as an ichnological window on small tetrapod activity and based on diversity, abundance and high-quality preservation, is regarded as an exceptional Konservat-Lagerstätten.

Author Correction: Exquisitely-preserved, high-definition skin traces in diminutive theropod tracks from the Cretaceous of Korea.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Exquisitely-preserved, high-definition skin traces in diminutive theropod tracks from the Cretaceous of Korea.

Small theropod tracks, ichnogenus Minisauripus, from the Jinju Formation (Cretaceous) of Korea reveal exquisitely preserved skin texture impressions. This is the first report for any dinosaur of skin traces that cover entire footprints, and every footprint in a trackway. Special sedimentological conditions allowed footprint registration without smearing of skin texture patterns which consist of densely-packed, reticulate arrays of small (<0.5 mm) polygons, preserved as both impressions and casts, the latter essentially foot replicas. The skin texture resembles that reported for two Lower Cretaceous avian theropods (birds) from China which had quite different foot morphologies. This is also the oldest report of Minisauripus from Korea predating five reports from the Haman Formation of inferred Albian age. Minisauripus is now known from six Korean and three Chinese localities, all from the Lower Cretaceous. This gives a total sample of ~95 tracks representing ~54 trackways. With >80% of tracks <3.0 cm long, Minisauripus is pivotal in debates over whether small tracks represent small species, as the database suggests, or juveniles of large species.

Smallest known raptor tracks suggest microraptorine activity in lakeshore setting.

Ongoing studies of a multiple track-bearing horizons from massive excavations in the Jinju Formation (Lower Cretaceous) of South Korea have yielded a remarkable diversity of avian, non-avian dinosaur, pterosaur, crocodilian and mammal tracks, many very small and well preserved. Here we report diminutive, didactyl tracks (~1.0 cm long) assigned to a new dromaeosaurid ichnogenus Dromaeosauriformipes, which resembles the larger, but still quite small, ichnogenus Dromaeosauripus, also from the same formation only 30 km away. These diminutive tracks are consistent with the foot size of smaller dromaeosaurid taxa like Early Cretaceous Microraptor from China, and may represent diminutive species or juveniles of larger species. The association of tracks with lakeshore sediments is consistent with the evidence that Microraptor was a fish eater. Two trackways and isolated tracks indicate variable trackmaker gaits and speeds. If oviparous, as assumed for most non-avian dinosaur neonates, the trackmakers must have hatched from tiny eggs. Previous studies of the Korean Cretaceous indicate the presence of other diminutive (~1.0 cm long) theropod tracks (Minisauripus). Such occurrences strongly suggest that small tracks attributed to juveniles, or very small tetrapod species, are more common than previously supposed especially where suitable preservation conditions prevailed.

A New Pleistocene Hominin Tracksite from the Cape South Coast, South Africa.

A Late Pleistocene hominin tracksite has been identified in coastal aeolianite rocks on the Cape south coast of South Africa, an area of great significance for the emergence of modern humans. The tracks are in the form of natural casts and occur on the ceiling and side walls of a ten-metre long cave. Preservation of tracks is of variable quality. Up to forty hominin tracks are evident. Up to thirty-five hominin tracks occur on a single bedding plane, with potential for the exposure of further tracks. Five tracks are apparent on a second hominin track-bearing bedding plane. A number of individuals made the tracks while moving down a dune surface. A geological investigation at the site and stratigraphic comparison to published geochronological studies from this area suggest that the tracks are ~90 ka in age. If this is the case, the shoreline at the time would have been approximately 2 km distant. This is the first reported hominin tracksite from this time period. It adds to the relatively sparse global record of early hominin tracks, and represents the largest and best preserved archive of Late Pleistocene hominin tracks found to date. The tracks were probably made by Homo sapiens.

A diverse mammal-dominated, footprint assemblage from wetland deposits in the Lower Cretaceous of Maryland.

A newly discovered assemblage of predominantly small tracks from the Cretaceous Patuxent Formation at NASA's Goddard Space Flight Center, Maryland, reveals one of the highest track densities and diversities ever reported (~70 tracks, representing at least eight morphotypes from an area of only ~2 m2). The assemblage is dominated by small mammal tracks including the new ichnotxon Sederipes goddardensis, indicating sitting postures. Small crow-sized theropod trackways, the first from this unit, indicate social trackmakers and suggest slow-paced foraging behavior. Tracks of pterosaurs, and other small vertebrates suggest activity on an organic-rich substrate. Large well-preserved sauropod and nodosaurs tracks indicate the presence of large dinosaurs. The Patuxent Formation together with the recently reported Angolan assemblage comprise the world's two largest Mesozoic mammal footprint assemblages. The high density of footprint registration at the NASA site indicates special preservational and taphonomic conditions. These include early, penecontemporaneous deposition of siderite in organic rich, reducing wetland settings where even the flesh of body fossils can be mummified. Thus, the track-rich ironstone substrates of the Patuxent Formation, appear to preserve a unique vertebrate ichnofacies, with associated, exceptionally-preserved body fossil remains for which there are currently no other similar examples preserved in the fossil record.

Mummified precocial bird wings in mid-Cretaceous Burmese amber.

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans.

Digit-only sauropod pes trackways from China--evidence of swimming or a preservational phenomenon?

For more than 70 years unusual sauropod trackways have played a pivotal role in debates about the swimming ability of sauropods. Most claims that sauropods could swim have been based on manus-only or manus-dominated trackways. However none of these incomplete trackways has been entirely convincing, and most have proved to be taphonomic artifacts, either undertracks or the result of differential depth of penetration of manus and pes tracks, but otherwise showed the typical pattern of normal walking trackways. Here we report an assemblage of unusual sauropod tracks from the Lower Cretaceous Hekou Group of Gansu Province, northern China, characterized by the preservation of only the pes claw traces, that we interpret as having been left by walking, not buoyant or swimming, individuals. They are interpreted as the result of animals moving on a soft mud-silt substrate, projecting their claws deeply to register their traces on an underlying sand layer where they gained more grip during progression. Other sauropod walking trackways on the same surface with both pes and manus traces preserved, were probably left earlier on relatively firm substrates that predated the deposition of soft mud and silt . Presently, there is no convincing evidence of swimming sauropods from their trackways, which is not to say that sauropods did not swim at all.

Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs.

Relationships between non-avian theropod dinosaurs and extant and fossil birds are a major focus of current paleobiological research. Despite extensive phylogenetic and morphological support, behavioural evidence is mostly ambiguous and does not usually fossilize. Thus, inferences that dinosaurs, especially theropods displayed behaviour analogous to modern birds are intriguing but speculative. Here we present extensive and geographically widespread physical evidence of substrate scraping behavior by large theropods considered as compelling evidence of "display arenas" or leks, and consistent with "nest scrape display" behaviour among many extant ground-nesting birds. Large scrapes, up to 2 m in diameter, occur abundantly at several Cretaceous sites in Colorado. They constitute a previously unknown category of large dinosaurian trace fossil, inferred to fill gaps in our understanding of early phases in the breeding cycle of theropods. The trace makers were probably lekking species that were seasonally active at large display arena sites. Such scrapes indicate stereotypical avian behaviour hitherto unknown among Cretaceous theropods, and most likely associated with terrirorial activity in the breeding season. The scrapes most probably occur near nesting colonies, as yet unknown or no longer preserved in the immediate study areas. Thus, they provide clues to paleoenvironments where such nesting sites occurred.

An Ornithopod-Dominated Tracksite from the Lower Cretaceous Jiaguan Formation (Barremian-Albian) of Qijiang, South-Central China: New Discoveries, Ichnotaxonomy, Preservation and Palaeoecology.

The historically-famous Lotus Fortress site, a deep 1.5-3.0-meter-high, 200-meter-long horizonal notch high up in near-vertical sandstone cliffs comprising the Cretaceous Jiaguan Formation, has been known since the 13th Century as an impregnable defensive position. The site is also extraordinary for having multiple tetrapod track-bearing levels, of which the lower two form the floor of part of the notch, and yield very well preserved asseamblages of ornithopod, bird (avian theropod) and pterosaur tracks. Trackway counts indicate that ornithopods dominate (69%) accounting for at least 165 trackmakers, followed by bird (18%), sauropod (10%), and pterosaur (3%). Previous studies designated Lotus Fortress as the type locality of Caririchnium lotus and Wupus agilis both of which are recognized here as valid ichnotaxa. On the basis of multiple parallel trackways both are interpreted as representing the trackways of gregarious species. C. lotus is redescribed here in detail and interpreted to indicate two age cohorts representing subadults that were sometimes bipedal and larger quadrupedal adults. Two other previously described dinosaurian ichnospecies, are here reinterpreted as underprints and considered nomina dubia. Like a growing number of significant tetrapod tracksites in China the Lotus Fortress site reveals new information about the composition of tetrapod faunas from formations in which the skeletal record is sparse. In particular, the site shows the relatively high abundance of Caririchium in a region where saurischian ichnofaunas are often dominant. It is also the only site known to have yielded Wupus agilis. In combination with information from other tracksites from the Jiaguan formation and other Cretaceous formations in the region, the track record is proving increasingly impotant as a major source of information on the vertebrate faunas of the region. The Lotus Fortress site has been developed as a spectacular, geologically-, paleontologically- and a culturally-significant destination within Qijiang National Geological Park.

Reanalysis of Wupus agilis (Early Cretaceous) of Chongqing, China as a Large Avian Trace: Differentiating between Large Bird and Small Non-Avian Theropod Tracks.

Trace fossils provide the only records of Early Cretaceous birds from many parts of the world. The identification of traces from large avian track-makers is made difficult given their overall similarity in size and tridactyly in comparison with traces of small non-avian theropods. Reanalysis of Wupus agilis from the Early Cretaceous (Aptian-Albian) Jiaguan Formation, one of a small but growing number of known avian-pterosaur track assemblages, of southeast China determines that these are the traces of a large avian track-maker, analogous to extant herons. Wupus, originally identified as the trace of a small non-avian theropod track-maker, is therefore similar in both footprint and trackway characteristics to the Early Cretaceous (Albian) large avian trace Limiavipes curriei from western Canada, and Wupus is reassigned to the ichnofamily Limiavipedidae. The reanalysis of Wupus reveals that it and Limiavipes are distinct from similar traces of small to medium-sized non-avian theropods (Irenichnites, Columbosauripus, Magnoavipes) based on their relatively large footprint length to pace length ratio and higher mean footprint splay, and that Wupus shares enough characters with Limiavipes to be reassigned to the ichnofamily Limiavipedidae. The ability to discern traces of large avians from those of small non-avian theropods provides more data on the diversity of Early Cretaceous birds. This analysis reveals that, despite the current lack of body fossils, large wading birds were globally distributed in both Laurasia and Gondwana during the Early Cretaceous.

Hints of the early Jehol Biota: important dinosaur footprint assemblages from the Jurassic-Cretaceous boundary Tuchengzi Formation in Beijing, China.

New reports of dinosaur tracksites in the Tuchengzi Formation in the newly established Yanqing Global Geopark, Beijing, China, support previous inferences that the track assemblages from this formation are saurischian-dominated. More specifically, the assemblages appear theropod-dominated, with the majority of well-preserved tracks conforming to the Grallator type (sensus lato), thus representing relatively small trackmakers. Such ichnofaunas supplement the skeletal record from this unit that lacks theropods thus far, proving a larger diversity of dinosaur faunas in that region. Sauropods are represented by medium to large sized and narrow and wide-gauge groups, respectively. The latter correspond with earlier discoveries of titanosauriform skeletons in the same unit. Previous records of ornithischian tracks cannot be positively confirmed. Purported occurrences are re-evaluated here, the trackways and imprints, except of a single possible specimen, re-assigned to theropods. Palecologically the Tuchengzi ichnofauna is characteristic of semi-arid fluvio-lacustrine inland basins with Upper Jurassic-Lower Cretaceous deposits in northern China that all show assemblages with abundant theropod and sauropod tracks and minor components of ornithopod, pterosaur and bird tracks.

A 'terror of tyrannosaurs': the first trackways of tyrannosaurids and evidence of gregariousness and pathology in Tyrannosauridae.

The skeletal record of tyrannosaurids is well-documented, whereas their footprint record is surprisingly sparse. There are only a few isolated footprints attributed to tyrannosaurids and, hitherto, no reported trackways. We report the world's first trackways attributable to tyrannosaurids, and describe a new ichnotaxon attributable to tyrannosaurids. These trackways are from the Upper Cretaceous (Campanian - Maastrichtian) of northeastern British Columbia, Canada. One trackway consists of three tridactyl footprints, and two adjacent trackways consist of two footprints each. All three trackways show animals bearing southeast within an 8.5 meter-wide corridor. Similarities in depth and preservation of the tyrannosaurid tracks indicate that these three trackways were made by track-makers walking concurrently in the same direction. These trackways add significantly to previous osteology-based hypotheses of locomotion and behavior in Tyrannosauridae by providing ichnologic support for gregariousness in tyrannosaurids, and the first record of the walking gait of tyrannosaurids.

Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace.

BACKGROUND: Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. METHODOLOGY/PRINCIPAL FINDINGS: Here we describe a well-preserved theropod trackway in a Lower Jurassic ( approximately 198 million-year-old) lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. CONCLUSIONS/SIGNIFICANCE: The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods.