Sauropod tracks from the Middle Jurassic Chuanjie Formation of Yunnan Province and the pre-Cretaceous sauropodomorph trackways from China

The Xixipo dinosaur tracksite in the Chuanjie Formation of Yunnan Province is one of the 14 Chinese sites yielding sauropod tracks from between the Triassic–Jurassic and Jurassic–Cretaceous boundaries, but is only one of the two that represent the Middle Jurassic. Although it is a small site, it adds incrementally to the overall track record of the region and allows comparison with the body fossil record and classification of the Chuanjie Formation as a Type 3b or Type 4b deposit in which both the body fossil and trace fossil record, in this case representing sauropodomorphs, are similar in composition and frequency of occurrence. We argue that the sauropod trace and body fossil records, while based on different categories of evidence, are very important. Integrating and correlating all available data from both records increases our understanding of sauropod communities, and both are equally valuable for this. In addition, we also discuss narrow to wide gauge, coeval sauropod trackways from China, and the relationship between the potential trackmaker of China's Jurassic Brontopodus-type trackways and mamenchisaurids and, beginning from the Late Jurassic, representatives of this type and titanosauriform sauropods.     

First Jurassic dinosaur tracksite from Guizhou Province,China: morphology,trackmaker and paleoecology

Abstract

Sauropod tracks from the Early Jurassic Maanshan Member of the Ziliujing Formation in the Dazhuanwan area of Guizhou represent the first Jurassic dinosaur track record for this province. The best preserved and longest trackway is narrow gauge (Brontopodus type), and indicates a relatively small trackmaker (footprint length ~35.0 cm). In conjunction with sauropodomorph skeletal remains these tracks suggest that basal sauropodomorphs and primitive sauropods coexisted in this region during the Early Jurassic. This pattern is same in the Lufeng and Sichuan basins. Thus, sauropod tracks from southwest China are diverse in the Early Jurassic, and include narrow gauge Parabrontopodus, wide gauge Brontopodus-type, and basal sauropodomorph tracks.     

A theropod–sauropod track assemblage from the ?Middle–Upper Jurassic Shedian Formation at Shuangbai,Yunnan Province,China, reflecting different sizes of trackmakers: Review and new observations

A dinosaur tracksite at Hemenkou (Shuangbai County, Yunnan Province) in the ?Middle–Upper Jurassic Shedian Formation that consists mainly of gray-purple feldspathic quartz sandstones was previously reported incorrectly as being in the Lower Cretaceous Puchanghe Formation. The previous assignment is also inconsistent with two regional geological maps. Although mostly yielding poorly preserved tracks, the site nevertheless indicates a diversity of theropod and sauropod trackmakers partly consistent with the Late Jurassic body fossils from the region. Purported ornithopod are re-evaluated here as those of theropods. The theropod tracks and trackways show distinct similarities to those of the Grallator–Eubrontes plexus and can be subdivided into three morphotypes that may reflect different pes anatomy and/or substrate conditions. Two sizes of tracks (small, large) indicate the presence of different size classes or species in this area in the Late Jurassic. Similarly, the sauropod trackways document three differently sized trackmakers (small–medium–large) showing a typical wide-gauge (Brontopodus) pattern. The track record is the first evidence of theropods in the ?Middle–Late Jurassic of central Yunnan, whereas the sauropod tracks suggest a relation to the coeval basal eusauropods known from this region by skeletal remains.     

A New Basal Sauropod Dinosaur from the Middle Jurassic of Niger and the Early Evolution of Sauropoda

Background

The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification.

Principal Findings

A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography.

Conclusions

Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.     

Dinosaurs of Switzerland

Until 1960, the record of dinosaurs was rather poor in Switzerland. Between 1960 and 1980, several new localities with plateosaurid remains as well as prosauropod and theropod tracks were found in Late Triassic sabkha and floodplain environments. The discovery of large surfaces with sauropod tracks in the Late Jurassic of the Jura Mountains in 1987 triggered a stream of new data. More than 20 new localities with tracks from both sauropod and theropod dinosaurs in different stratigraphic levels have been found since then. The latest discoveries include trackways of iguanodontids from the Early Cretaceous of the central Swiss Alps and a large Late Jurassic surface with trackways of small sauropods in the northernmost part of the Jura Mountains. The best skeletal record comes from the Late Triassic, with scattered data from the Late Jurassic. The track and trackway record appears to be best in the Late Jurassic. To cite this article: C.A. Meyer, B. Thüring, C. R. Palevol 2 (2003) 103–117.     

Theropod and Ornithischian Footprints from the Middle Jurassic Yanan Formation of Zizhou County,Shaanxi, China

New tracksites reported from the Zizhou area elucidate the nature of the Early-Middle Jurassic dinosaurian ichnofaunas in Shaanxi Province. The assemblage is composed of footprints and trackways of medium- to large-sized theropods that show similarities with both the ichnogenera Kayentapus and Eubrontes and of small bipedal ornithischians that are referred to AS Anomoepus isp. Additionally tracks of a quadruped are present and assigned to Deltapodus isp. that may be related to a stegosaurian. Anomoepus isp. is similar to the holotype of Shensipus tungchuanensis which is, although apparently lost, re-assigned here and considered to be a subjective junior synonym of Anomoepus. It is therefore placed in new combination as Anomoepus tungchuanensis comb. nov. Identical tracks have been reported from well-preserved trackways both in the Zizhou and Shenmu areas, where they also co-occur with theropod tracks (Kayentapus and Grallator) and tracks of quadrupedal ornithischians (Shenmuichnus and Deltapodus). Thus, it appears that the carbonaceous (coal-bearing) facies of the region reveal ichnofaunas with both relatively abundant saurischian (theropod) and ornithischian tracks. This is in contrast with many areas where the ichnofaunas are heavily or exclusively saurischian (theropod) dominated.     

The first record of Anomoepus tracks from the Middle Jurassic of Henan Province,Central China

Small, gracile mostly tridactyl tracks from the Middle Jurassic of Henan Province represent the first example of the ichnogenus Anomoepus from this region. They represent a growing number of reports (at least eight) of this ichnogenus from the Jurassic of China. In conjunction with Changpeipus and Eubrontes, they appear characteristic of known global footprint biochrons. Anomoepus indicates the presence of ornithischian dinosaurs that are often scarce or unknown from skeletal remains in coeval deposits. When first discovered, these tracks were informally referred to as bird tracks. This interpretation reflects convergence between small Jurassic Anomoepus and avian theropod tracks that are hitherto known only from the Cretaceous and the Cenozoic. However, most Anomoepus are larger and more robust than any hitherto known Mesozoic avian tracks.     

A New Sauropod Dinosaur from the Middle Jurassic of the United Kingdom

A new record of a sauropodomorph dinosaur is here described from the Middle Jurassic (Aalenian) Saltwick Formation of Whitby (Yorkshire), UK. A single caudal vertebra represents an early sauropodomorph and signifies the earliest recognised eusauropod dinosaur from the United Kingdom. The absence of pleurocoels and a narrow, dorsoventrally deep, but craniocaudally short centrum, suggests a primitive sauropodomorph. Distinct spinopostzygopophyseal laminae rise from the lateral margins of the postzygapophyses and pass caudally along what remains of the neural spine, a character unique to a subgroup of sauropods that includes Barapasaurus, Omeisaurus and other neosauropods and eusauropods. The lack of phylogenetically robust characters in sauropod caudal vertebrae usually makes it difficult to establish affinities, but the absence of mild procoely excludes this specimen from both Diplodocoidea and Lithostrotia. The vertebra cannot be further distinguished from those of a wide range of basal sauropods, cetiosaurids and basal macronarians. However, this plesiomorphic vertebra still signifies the earliest stratigraphic occurrence for a British sauropod dinosaur.     

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.     

Dinosaur footprints from the Phra Wihan Formation (Early Cretaceous of Thailand)

The ichnological assemblage of the Phra Wihan Formation (early Early Cretaceous of northeastern Thailand) includes the first sauropod tracks ever found in Thailand. It is reminiscent of the fauna of the underlying Jurassic Phu Kradung Formation with theropods, small ornithischians of uncertain affinities (possibly Hypsilophodon-like ornithopods) and sauropods. It suggests that, in southeastern Asia, an important faunal change occurred in the Early Cretaceous among continental vertebrates, whereas little happened at the Jurassic–Cretaceous boundary.     

A Middle Jurassic dinosaur trackway site from Oxfordshire, UK

The Middle Jurassic (Bathonian) Ardley trackway site in Oxfordshire, UK is described in detail. The track site is extensive, containing over 40 more-or-less continuous theropod and sauropod trackways preserved together on a single bedding plane with some trackways up to 180 m in length. The trackways display reasonable preservation, with claw marks discernible. Sauropod trackways are by far the most abundant and are representative of taxa that exhibit both narrow and wide-gauge styles of locomotion. Theropod trackways are represented by large tridactyl prints and claw impressions that display exceptionally low pace angulation values during their walking phase. One theropod trackway is unique in that it reveals a gait transition associated with a temporary increase of speed. These dinosaurs were walking over a lime-mud firmground to hardground that was emergent, or locally very shallowly submerged. GPS (Global Positioning Satellite) data reveal that the tracks, preserved during a short time interval, trend in a north-easterly direction. Multi-herding behaviour is suggested for the sauropods of differing size. The discovery of this site adds significantly to our knowledge of the taxonomic composition of Middle Jurassic ecosystems. Evidence concerning locomotor styles employed by saurischian dinosaurs, footprint identification, potential trackmaker, social interactions and observations concerning estimates of Middle Jurassic faunal diversity, as well as aspects of dinosaur locomotor evolution are discussed.     

Complex In-Substrate Dinosaur (Sauropoda,Ornithopoda) Foot Pathways Revealed by Deep Natural Track Casts from the Lower Cretaceous Xiagou and Zhonggou Formations,Gansu Province,China

Several new Early Cretaceous tracksites from the Lower Cretaceous Xiagou Formation of Gansu Province (China) with tracks of large sauropods and ornithopods are described. Previously reported bird tracks were missing due to human negligence. The studied specimens are preserved as impressions and shallow and deep natural track casts. These dinosaur tracks are first reported from the Jiuquan area in the Changma Basin, matching well with the skeletal record of diverse non-avian dinosaur-bird faunas of this region. Moreover, they add new data to the dinosaur ichnofaunas of the Lanzhou-Minhe Basin (Gansu Province) and indicate a wide distribution of dinosaur-bird assemblages in the Early Cretaceous. Regarding morphology, sauropod, and ornithopod tracks from the Lanzhou-Minhe Basin and the Jiuquan area are very similar to each other. Titanosauriform trackmakers are assumed for the sauropod tracks and possibly iguanodontids have left the large, tridactyl ornithopod tracks. Of particular interest are well-preserved, deep natural track casts of large ornithopods and sauropods preserving ridges and grooves as well as striation marks on the lateral sides of the casts that allow the reconstruction of complex pathways of the foot within the substrate. One particular sauropod pes–manus track cast even indicates lateral and vertical sliding within the sediment because of the presence of “double impressions of digits” on the bottom.     

New dinosaur tracksites from the Middle Jurassic of Madagascar: ichnotaxonomical,behavioural and palaeoenvironmental implications

Abstract: New dinosaur tracksites are described from the Bajocian–Bathonian Bemaraha Formation of western Madagascar. Two track‐bearing surfaces can be followed over a distance of at least 4 km, suggesting the existence of a hitherto unrecognized megatracksite. The track assemblage is theropod dominated, but sauropod tracks also occur at one site. Qualitative and quantitative analysis of the abundant theropod track material suggests that most, if not all, theropod footprints are attributable to a single trackmaker and are referred to Kayentapus isp. Although this ichnogenus, originally described from the Lower Jurassic of North America, has never been recorded from Gondwana nor from the Middle Jurassic, track morphology strongly suggests this attribution. Palaeogeographical, sedimentological and ichnological data suggest that the dinosaur tracks formed in an intertidal to supratidal setting where the coastline influenced the preferred walking direction of the animals.     

Small theropod teeth from the Upper Jurassic coal mine of Guimarota (Portugal)

Isolated teeth of small theropod dinosaurs from the Upper Jurassic lignite coal mine of Guimarota (near Leiria, Portugal) are described and illustrated. The well known Upper Jurassic theropods from Europe,Archaeopteryx andCompsognathus, are the most common taxa in the Guimarota assemblage. One morphotype is closely related to an allosaurid theropod. Six further morphotypes of theropod teeth are also described, which are closely related to Cretaceous theropods such as dromaeosaurids, troodontids, tyrannosaurids,Richardoestesia andParonychodon. A Late Jurassic origin of these groups of theropods, which is very often postulated, is discussed.     

Cranial anatomy of Shunosaurus, a basal sauropod dinosaur from the Middle Jurassic of China

Shunosaurus, from the Middle Jurassic of China, is probably the best‐known basal sauropod and is represented by several complete skeletons. It is unique among sauropods in having a small, bony club at the end of its tail. New skull material provides critical information about its anatomy, brain morphology, tooth replacement pattern, feeding habits and phylogenetic relationships. The skull is akinetic and monimostylic. The brain is relatively small, narrow and primitively designed. The tooth replacement pattern exhibits back to front replacement waves in alternating tooth position. The teeth are spatulate, stout and show well‐developed wear facets indicative of coarser plant food. Upper and lower tooth rows interdigitate and shear past each other. Tooth morphology, skull architecture, and neck posture indicate that Shunosaurus was adapted to ground feeding or low browsing. Shunosaurus exhibits the following cranial autapomorphies: emargination of the ventral margin of the jugal/quadratojugal bar behind the tooth row; postorbital contains a lateral pit; vomers do not participate in the formation of the choanae; pterygoid is extremely slender and small with a dorsal fossa; quadrate ramus of the pterygoid is forked; quadratojugal participates in the jaw articulation; tooth morphology is a combination of cylindrical and spatulate form; basipterygoid process is not wrapped by the caudal process of the pterygoid; trochlear nerve has two exits; occlusal level of the maxillary tooth row is convex downward, whereas that of the dentary is concave upward, acting like a pair of garden shears; dentary tooth count is 25 or more; and the replacing teeth invade the labial side of the functional teeth. Cranial characters among the basal sauropods are reviewed. As Shunosaurus is the earliest sauropod for which cranial remains are known, it occupies an important position phylogenetically, showing the modification of skull morphology from the prosauropod condition. Although the skull synapomorphies of Sauropoda are unknown at present, 27 cranial synapomorphies are known for the clade Eusauropoda. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136 , 145?169.     

First Thyreophoran Type Tracks from the Middle Jurassic Chuanjie Formation of Yunnan Province,China

Two tridactyl footprints from the Chuanjie Formation (Middle Jurassic) of Yunnan Province, China are morphological characteristics of thyreophoran tracks. They show some similarities to Shenmuichnus, known from the Early Jurassic strata of both Shaanxi and Yunnan provinces, but are somewhat larger, thereby resembling the ichnogenus Stegopodus. Based on their general morphology and size being congruent with this ichnogenus, they are tentatively assigned here to cf. Stegopodus. This is the fourth report of large ornithischian (probably thyreophoran) tracks from the Lower-Middle Jurassic of China that indicates relatively large trackmakers that were likely to be taxonomically distinct from much smaller and gracile Anomoepus trackmakers, also of ornithischian affinity. The larger tracks indicate a hitherto unreported abundance, size range and diversity of track types attributed to this group. The parallel orientation of the two best preserved trackways may indicate gregariousness.     

A new sauropodomorph dinosaur from the Early Jurassic of Patagonia and the origin and evolution of the sauropod-type sacrum

Background

The origin of sauropod dinosaurs is one of the major landmarks of dinosaur evolution but is still poorly understood. This drastic transformation involved major skeletal modifications, including a shift from the small and gracile condition of primitive sauropodomorphs to the gigantic and quadrupedal condition of sauropods. Recent findings in the Late Triassic–Early Jurassic of Gondwana provide critical evidence to understand the origin and early evolution of sauropods.

Methodology/Principal Findings

A new sauropodomorph dinosaur, Leonerasaurus taquetrensis gen. et sp. nov., is described from the Las Leoneras Formation of Central Patagonia (Argentina). The new taxon is diagnosed by the presence of anterior unserrated teeth with a low spoon-shaped crown, amphicoelous and acamerate vertebral centra, four sacral vertebrae, and humeral deltopectoral crest low and medially deflected along its distal half. The phylogenetic analysis depicts Leonerasaurus as one of the closest outgroups of Sauropoda, being the sister taxon of a clade of large bodied taxa composed of Melanorosaurus and Sauropoda.

Conclusions/Significance

The dental and postcranial anatomy of Leonerasaurus supports its close affinities with basal sauropods. Despite the small size and plesiomorphic skeletal anatomy of Leonerasaurus, the four vertebrae that compose its sacrum resemble that of the large-bodied primitive sauropods. This shows that the appearance of the sauropod-type of sacrum predated the marked increase in body size that characterizes the origins of sauropods, rejecting a causal explanation and evolutionary linkage between this sacral configuration and body size. Alternative phylogenetic placements of Leonerasaurus as a basal anchisaurian imply a convergent acquisition of the sauropod-type sacrum in the new small-bodied taxon, also rejecting an evolutionary dependence of sacral configuration and body size in sauropodomorphs. This and other recent discoveries are showing that the characteristic sauropod body plan evolved gradually, with a step-wise pattern of character appearance.     

A diversified vertebrate ichnite fauna from the Dasheng Group (Lower Cretaceous) of southeast Shandong Province,China

The Qingquan dinosaur tracksite, from the Lower Cretaceous Dasheng Group, Shandong Province, China adds to the growing record of saurischian-dominated ichnofaunas of the region. The site reveals the presence of avian theropods (Koreanaornis) and non-avian theropods tentatively referred to Jialingpus. Sauropod tracks are referred to Brontopodus. One site shows evidence of extensive trampling attributable to sauropods and theropods that moved in the same westerly direction, though not necessarily at exactly the same time. This site is reminiscent of the famous Davenport Ranch site in Texas which has provoked much debate about the herding behavior of sauropods as a defense strategy against theropod predators.