Theropod Research Articles

Convergent dental adaptations in the serrations of hypercarnivorous synapsids and dinosaurs.

Theropod dinosaurs are well known for having a ziphodont dentition: serrated, blade-shaped teeth that they used for cutting through prey. Serrations along the carinae of theropod teeth are composed of true denticles, a complex arrangement of dentine, enamel, and interdental folds. This structure would have supported individual denticles and dissipated the stresses associated with feeding. These particular serrations were previously thought to be unique to theropod dinosaurs and some other archosaurs. Here, we identify the same denticles and interdental folds forming the cutting edges in the teeth of a Permian gorgonopsian synapsid, extending the temporal and phylogenetic distribution of this dental morphology. This remarkable instance of convergence not only represents the earliest record of this adaptation to hypercarnivory but also demonstrates that the first iteration of this feature appeared in non-mammalian synapsids. Comparisons of tooth serrations in gorgonopsians with those of earlier synapsids and hypercarnivorous mammals reveal some gorgonopsians acquired a complex tissue arrangement that differed from other synapsids.

WITHDRAWN: A maned theropod dinosaur from Gondwana with elaborate integumentary structures

Abstract Discoveries of dinosaurs with integumentary structures over the last few decades have revolutionised our understanding of the phylogenetic relationships between birds and dinosaurs as well as the origin and evolution of feathers. A remarkable number of dinosaurs have been discovered with a diverse range of preserved integumentary structures. Several of these dinosaurs are adorned with elaborate integumentary structures that have been linked to behaviours including thermoregulation, egg incubation, and sexual display. Among Theropoda, such elaborate structures have only been previously recorded within Maniraptoriformes. However, elaborate monofilamentous structures are also present in some small ornithischians. The majority of theropods preserving integumental structures come from the Upper Jurassic and Lower Cretaceous of China or the Upper Jurassic of southern Germany, and all are of Laurasian origin. Herein, we describe a new genus and species of compsognathid theropod from the Lower Cretaceous (Aptian) Crato Formation of Northeast Brazil, representing the first Gondwanan non-avian theropod with preserved filamentous integumentary structures. It is also the first non-maniraptoran possessing elaborate integumentary structures that were most likely used for display. These include slender monofilaments associated with the base of the neck, increasing in length along the dorsal thoracic region where they form an impressive mane, as well as a pair of elongate, ribbon-like structures likely emerging from the shoulder. Such elaborate integumentary structures are hitherto unknown in any other dinosaur, although superficially similar elongate display feathers emerge from the carpal region of the male standardwing bird-of-paradise (Semioptera wallacii).

A new theropod dinosaur from a peculiar Late Triassic assemblage of southern Brazil

The early evolution of theropod dinosaurs is poorly understood. Whereas sauropodomorphs are well-known from the oldest dinosaur bearing outcrops, the record of theropods is fragmentary and ambiguous. The Triassic deposits from Brazil yielded some of the oldest dinosaurs worldwide. These dinosaurs came from two distinct Assemblage Zones (AZ): the Hyperodapedon AZ (Carnian) and the Riograndia AZ (early Norian). Here, a specimen previously assigned to cf. Dinosauromorpha is reassessed. CAPPA/UFSM 0157 comes from an enigmatic assemblage with predominance of the traversodotind cynodont Siriusgnathus. This assemblage has been tentatively assigned to the Riograndia AZ. However, the absence of index fossils still hampers a reliable assignation. The specimen, which comprises a proximal portion of a left femur, belongs to a new theropod taxon erected here as Erythrovenator jacuiensis gen. et sp. nov. The new dinosaur differs from all other known Triassic dinosaurs based on the absence of a raised dorsolateral trochanter of the femur. Erythrovenator jacuiensis gen. et sp. nov. is regarded as a theropod on the basis of the pyramidal shape of the anterior trochanter in anterior view. The results of a phylogenetic analysis corroborate this assignation. Therefore, the new dinosaur represents one of the oldest theropod dinosaurs worldwide, shedding lights on some of the earliest theropod features. Finally, the new specimen also represents the first carnivorous dinosaur from the assemblage dominated by the traversodontid cynodont Siriusgnathus, increasing our knowledge of the faunal content of this enigmatic assemblage.

New manual unguals of Trierarchuncus prairiensis from the Hell Creek Formation, Montana, and the ontogenetic development of the functional alvarezsaurid hand claw

The Alvarezsauridae comprise a clade of small-bodied theropod dinosaurs with highly-specialized skeletal adaptations, primarily reduced but proportionately robust forelimbs which have been hypothesized as relating to an insectivorous ecology. Alvarezsaurids are known predominantly from Mongolia, China, and South America, with a comparatively sparse North American record, where alvarezsaurid remains are among the most rarely recovered vertebrate fossils from the Upper Cretaceous Western Interior. North American alvarezsaurids include Albertonykus borealis from the lower Maastrichtian Horseshoe Canyon Formation of Alberta, Canada, known from a partial skeleton and additional isolated remains, and the recently named Trierarchuncus prairiensis from the upper Maastrichtian Hell Creek Formation of eastern Montana, USA, known previously from isolated specimens, including three manual D-I unguals, a partial radius, and a partial metatarsal III. Here we describe two new manual D-I unguals referable to the alvarezsaurid Trierarchuncus from the Hell Creek Formation of eastern Montana, USA. These new unguals contribute additional detail to the currently known ontogenetic series of Trierarchuncus manual D-I unguals and indicate the sequence and degree of change that occurred through growth within these alvarezsaurid hand claws. These changes appear to be modifications and reinforcement related to stresses induced from the hypothesized ecology of alvarezsaurids as insectivores which would tear apart substrates in search of insect prey, and as such can be characterized as ecologically-driven ontogenetic changes. Additionally, we demonstrate morphological indicators for determining whether isolated alvarezsaurid manual D-I unguals pertain to the right or left manus.

Feeding traces on postcranial sauropod remains from Bajo de la Carpa Formation (Upper Cretaceous, Santonian), northern Neuquén Basin, Patagonia, Argentina

Bite marks in non-avian dinosaur fossil records can constitute the best evidence of predator-prey interactions even if they are uncommon, ambiguous, or of uncertain origin. In this contribution, we present new evidence of feeding traces on an isolated sauropod element from Bajo de la Carpa Formation outcrops (Upper Cretaceous, Santonian), northern Neuquén province, Patagonia, Argentina. The specimen is composed of a partial dorsal vertebral centrum (MAU-Pv–CO–651; deposited at the Museo Municipal Argentino Urquiza, Rincón de los Sauces, Neuquén, Argentina). We tentatively refer it to an indeterminate titanosaur sauropod due to the presence of an opisthocoelic articulation and an internal pneumatic camellate condition. Three kinds of marks are preserved on the lateroventral face of the centrum: large and deep parallel marks, small and shallow longitudinal marks, and deep oval holes that we tentatively consider as punctures. These fossil marks can be considered to be feeding traces produced by a large-bodied carnivore to deflesh the bone and/or to obtain bone nutrients, probably during a single scavenging event. The marks and the punctures on the vertebral centrum can be referred to a theropod dinosaur due to their pattern and distribution. Viavenator exxoni (Filippi et al., 2016) represents the most likely trace-maker candidate among the several theropod and crocodile taxa present in the Bajo de la Carpa Formation fossil record. The fossil feeding traces reported here improve our knowledge about the feeding behaviour of large scavengers in the north of the Neuquén Basin, at least during the Santonian.

An accumulation of dinosaur remains in fluvial deposits of Mulichinco Formation (lower Valanginian, Neuquén Basin), Patagonia, Argentina: Taphonomic and paleoenvironmental inferences

Although the Neuquén Basin (Argentina) has an extensive record of fossil vertebrates for the Upper Cretaceous, little is known about the Early Cretaceous vertebrate faunas. The Mulichinco Formation (early Valanginian), where some dinosaur bone sites were found, provides important additional insights into the composition of continental fauna of that age. Although osteological studies of sauropod and theropod dinosaurs have been published for this unit, no taphonomic studies have been reported to date. Here, we describe the biostratinomic processes that took place on an accumulation of bones found in rocks of the Mulichinco Formation and discuss the relationships between those remains and the environment in which the bones were buried. Taphonomic alteration mechanisms were estimated, including articulation, weathering, abrasion, integrity, bioerosion, transport, and orientation. We described thoroughly a sedimentological section and micro-sections that indicate the stratigraphic location and spatial arrangement of the remains. Three sub-environments in the inferred braided fluvial system were determined and three levels with bones showing different taphonomic attributes were identified within the accumulation. The lag deposits contain indeterminate bone remains with signs of significant transport and probably from different origins. On the other hand, the channel infill contains an articulated carcass of a sauropod and associated remains, of para-autochthonous origin, with no significant transport.

An Early Cretaceous theropod dinosaur from Brazil sheds light on the cranial evolution of the Abelisauridae

Abelisaurid theropods dominated the predator role across Gondwana during the Late Cretaceous. They are characterized by highly reduced forelimbs and one of the most specialized cranial morphologies among carnivorous dinosaurs, exemplified by a broad skull, short rostrum, high occipital region, and highly kinetic intramandibular joint, suggestive of a specialized feeding strategy. Late Cretaceous abelisaurids are known from some remarkably complete taxa with well-preserved skulls. However, little is known about the pattern of character transformation that led to their highly modified condition because there are no well-preserved abelisaurids before the Late Cretaceous. Here we report a basal abelisaurid from the Early Cretaceous of Brazil that preserves a complete skull and reveals an early stage in the cranial evolution of the group. It lacks the specialized temporal and mandibular features characteristic of derived abelisaurids, including the kinetic intramandibular joint and knob-like dorsal projection of the parietals.

A small Cretaceous crocodyliform in a dinosaur nesting ground and the origin of sebecids

Sebecosuchia was a group of highly specialized cursorial crocodyliforms that diversified during the Cretaceous and persist until the end of the Miocene. Their unique combination of cranial and post-cranial features indicates that they were active terrestrial predators that occupied the apex of the Late Cretaceous terrestrial ecosystems, even competing with theropod dinosaurs. Here, we report the discovery of the earliest sebecid worldwide, and the first from Eurasia, Ogresuchus furatus gen. et sp. nov., based on a semi-articulate specimen located in a titanosaurian sauropod nesting ground. The new taxon challenges current biogeographical models about the early dispersal and radiation of sebecid crocodylomorphs, and suggests an origin of the group much earlier than previously expected. Moreover, the new taxon suggests a potential convergent evolution between linages geographically isolated. Taphonomic evidences suggest that Ogresuchus died almost in the same place where fossilized, in a dinosaur nesting area. Biometric and morphologic observations lead to speculate that Ogresuchus could easily predate on sauropod hatchlings.

A small theropod dinosaur from the Lower Jurassic Lias Group of Charmouth, Dorset

Terrestrial reptile remains are rare in Early Jurassic deposits from the UK but include important records of early dinosaurs and pterosaurs. Here we report an isolated limb bone from the Charmouth Mudstone Formation (upper Sinemurian) of Charmouth, Dorset that was previously misidentified as a referred specimen of the pterosaur Dimorphodon macronyx. Comparisons with other Early Jurassic tetrapods indicate that this element is the fibula of a neotheropod dinosaur, representing one of only a handful of theropod remains from the Lias Group. Although the material is limited the fibula is distinct from other penecontemporaneous European theropods and might represent a new – though currently undiagnosable – taxon. This, alongside other isolated discoveries, indicates that there might have been a higher diversity of theropod taxa in the Early Jurassic of Europe than is generally appreciated.

A theropod dinosaur feeding site from the Upper Jurassic of the Junggar Basin, NW China

Direct evidence for theropod feeding behaviour is rare in the fossil record, and mainly limited to bite marks on bones. Here we describe a dinosaur assemblage from the lower part of the early Late Jurassic Qigu Formation at Liuhuanggou Gorge, southern Junggar Basin, NW China, which has yielded fragmentary remains of a large sauropod as well as four teeth of large-sized theropods and one tooth of a small-sized theropod. The sauropod bones show numerous bite marks that can be confidently linked to the large-sized theropod, probably a metriacanthosaurid. The abundance of the theropod bite marks on a single skeleton indicates that the sauropod carcass was probably fed on extensively. Some bones are completely crushed and occur in patches of hundreds of tiny individual fragments indicating that they were trampled repeatedly by large dinosaurs. Both the feeding traces and the trampling suggests that the sauropod carcass was exposed for a substantial amount of time before it was finally buried within the deposits of a well-drained floodplain. The traces and the distinct preservation of the sauropod remains offer valuable insights into the feeding behaviour of large-sized theropods within Late Jurassic continental ecosystems.

Taphonomic evidence supports an aquatic lifestyle for Spinosaurus

A new locality near Tarda on the northern margin of the Tafilalt, south eastern Morocco exposes extensive sequences of the Ifezouane and Aoufous formations of the fluvial Kem Kem Group (Cretaceous, ?Albian-Cenomanian) on the south western flank of Ikfh n’Oufza escarpment of the Hamada du Meski. The stratigraphic sequence here differs significantly from better known exposures of the Kem Kem Group in the southern Tafilalt, and includes a heterolithic sequence of alternating grey mudstones and fine sandstones and a thin (~1.5 m) marine limestone. The locality is noteworthy for three vertebrate-bearing horizons within the upper part of the Ifezouane Formation. The upper two (Sites 1 and 2 in ascending order) are dominated by dental remains of the sawfish Onchopristis and the semi-aquatic theropod dinosaur Spinosaurus. Significantly, the remains of terrestrial dinosaurs constitute less than 1% of the total dental assemblage at Site 1 and 5.6% at Site 2. At Site 2 teeth of Spinosaurus outnumber the rostral “teeth” of Onchopristis. The remarkably high abundance of spinosaur teeth compared to remains of terrestrial dinosaurs, and even some aquatic animals strongly supports Spinosaurus being a largely aquatic animal spending much of its life in water where its teeth were shed and preserved.

The evolution of the pectoral extrinsic appendicular and infrahyoid musculature in theropods and its functional and behavioral importance.

Birds have lost and modified the musculature joining the pectoral girdle to the skull and hyoid, called the pectoral extrinsic appendicular and infrahyoid musculature. These muscles include the levator scapulae, sternomandibularis, sternohyoideus, episternocleidomastoideus, trapezius, and omohyoideus. As non-avian theropod dinosaurs are the closest relatives to birds, it is worth investigating what conditions they may have exhibited to learn when and how these muscles were lost or modified. Using extant phylogenetic bracketing, osteological correlates and non-osteological influences of these muscles are identified and discussed. Compsognathids and basal Maniraptoriformes were found to have been the likeliest transition points of a derived avian condition of losing or modifying these muscles. Increasing needs to control the feather tracts of the neck and shoulder, for insulation, display, or tightening/readjustment of the skin after dynamic neck movements may have been the selective force that drove some of these muscles to be modified into dermo-osseous muscles. The loss and modification of shoulder protractors created a more immobile girdle that would later be advantageous for flight in birds. The loss of the infrahyoid muscles freed the hyolarynx, trachea, and esophagus which may have aided in vocal tract filtering.

Aerodynamics Show Membranous-Winged Theropods Were a Poor Gliding Dead-End

The bizarre Scansoriopterygidae theropods Yi and Ambopteryx are the only dinosaurs thought to have had skin stretched between elongate fingers that form a potential membranous wing. While these structures have been suggested to have been used in aerial locomotion, this has never been shown to be the case. Demonstrating this function is of great importance because if these wings permitted flight it would support the growing view that theropod dinosaurs evolved flight multiple times in distinctive ways before the origin of modern birds. Here using Laser-Stimulated Fluorescence imaging we re-evaluate the anatomy of Yi and integrate this new information into several different equation-based aerodynamic calculations covering flight potential, methods of take-off (terrestrial-based running, arboreal launch), and powered versus gliding flight capabilities. For the first time we test whether Yi and Ambopteryx had flight capabilities and if so how efficient and effective it was. We also evaluate wing-based behaviours including wing-assisted incline running (WAIR). We find that Yi and Ambopteryx were highly unlikely to have any form of powered flight and had limited gliding abilities compared to similar-sized living and fossil gliders. We find that both taxa could not take-off from a terrestrial setting, supporting the idea that they were likely arboreal. Compared to similar-sized early-diverging fossil paravians, like Archaeopteryx and Microraptor, Scansoriopterygidae show significant deficiencies and differences in flapping-based locomotion models that indicate a much less competent flight stroke with limited aerial abilities. Combining these findings, our results show that the Scansoriopterygidae are not models for the early evolution of bird flight and that their structurally distinct and inefficient wings differed greatly from contemporaneous paravians including the earliest birds. Instead, we propose that Scansoriopterygidae represent a unique but failed flight architecture of non-avialan theropods. These findings conform with emerging data supporting multiple independent origins of flight in modern lineages. They show that the battle to capture the vertebrate aerial morphospace in the Middle to Late Jurassic was a dynamic and complex one not restricted to pterosaurs and only one theropod lineage.

First record of a theropod (Dinosauria, Theropoda) from the Late Cretaceous of the Bauru Group, southern Goiás State, Brazil

The objective of this article is to describe the first record of a theropod carnivorous dinosaur from the Late Cretaceous of the Adamantina Formation (Bauru Group, Paraná Basin) in the south of the state of Goiás in the Midwest region of Brazil. The methodology of this work was based on a bibliographic survey about the characteristics of teeth of theropods and the geology of the region, in addition to the description and morphological comparisons. This specimen was found in a geodiversity site called Serra da Portaria, in the Paraúna State Park, municipality of Paraúna, where residuals from the Adamantina Formation is exposed. The specimen, a fragmentary tooth covered with iron oxide, but with a partially preserved crown, was assigned as a percentage to an undetermined theropod for having a labiolingually compressed crown and cross section. In addition to the Bauru Group in the state of Goiás, only remnants of sauropod herbivorous dinosaurs are known for the Adamantina and Marília formations, the tooth described here is the first osteological record of a theropod from the south of Goiás.

The first theropod dinosaur (Coelurosauria, Theropoda) from the base of the Romualdo Formation (Albian), Araripe Basin, Northeast Brazil

The Romualdo Formation (Araripe Basin) is worldwide known for the large number of well-preserved fossils but the dinosaur record is rather scarce. Here we describe a new coelurosaur, which is the first tetrapod recovered from the basal layers of this stratigraphic unit that consist of dark shales. Aratasaurus museunacionali gen. et sp. nov. is known by an incomplete but articulated right hind limb with the distal portion of the femur, proximal half of tibia and incomplete pes. The new species differs from other coelurosaurs by a medial fossa in the tibia and digits II, III and IV being symmetric. The phylogenetic analysis recovered Aratasaurus museunacionali closely related to Zuolong salleei, forming a basal coelurosaur lineage. The paleohistology indicate that the specimen is a juvenile, with an estimated body length around 3.12 m. The new taxon represents the first occurrence of basal coelurosaurians in the Araripe Basin and suggests a widespread distribution of this group during the Lower Cretaceous.

Chemical preservation of tail feathers fromAnchiornis huxleyi, a theropod dinosaur from the Tiaojishan Formation (Upper Jurassic, China)

AbstractA panel of geochemical techniques is used here to investigate the taphonomy of fossil feathers preserved in association with the skeleton of the Jurassic theropodAnchiornis huxleyi. Extant feathers were analysed in parallel to test whether the soft tissues morphologically preserved in the fossil also exhibit a high degree of chemical preservation. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicate that clays and iron oxide pseudomorphs occur in the surrounding sediment and also reveal the preservation of melanosome‐like microbodies in the fossil. Carbon gradient along a depth profile and co‐occurrence of carbon and sulphur are shown in the fossil by elastic backscattering (EBS) and particle‐induced x‐ray emission (PIXE), which are promising techniques for the elemental analysis of fossil soft tissues. The molecular composition of modern and fossil soft tissues was assessed from micro‐attenuated total reflectance fourier transform infrared spectroscopy (micro‐ATR FTIR), solid‐state13C nuclear magnetic resonance (CP‐MAS13C NMR) and pyrolysis gas chromatography mass spectrometry in the presence of TMAH (TMAH‐Py‐GC‐MS). Results indicate that the proteinaceous material that comprises the modern feathers is not present in the fossil feathers. The fossil feathers and the embedding sediment exhibit a highly aliphatic character. However, substantial differences exist between these samples, revealing that the organic matter of the fossil feathers is, at least partially, derived from original constituents of the feathers. Our results suggest that, despite the morphological preservation ofAnchiornisfeathers, original proteins, that is keratin, were probably not preserved in the 160‐myr‐old feathers.

An exceptional neurovascular system in abelisaurid theropod skull: New evidence from Skorpiovenator bustingorryi.

Abelisaurids were one of the most successful theropod dinosaurs during Cretaceous times. They are featured by numerous derived skull traits, such as heavily ornamented bones, short and tall snout, and a strongly thickened cranial roof. Furthermore, nasals are distinctive on having two distinct nasal patterns: strongly transversely convex and heavily sculptured (e.g., Carnotaurus), and transversely concave, with marked bilateral crests and poorly sculptured surfaces (e.g., Rugops). Independently of the pattern, some abelisaurid nasals (e.g., Rugops) show a distinctive row of large foramina on the dorsal surface, which were in general associated to skin structures (scales). Skorpiovenator bustingorryi is a derived abelisaurid coming from the upper Cretaceous beds of northwestern Patagonia, represented by an almost complete skeleton including a well-preserved skull. Particularly, the skull of Skorpiovenator shows nasal bones characterized by being transversely concave, rimmed by lateral crests and with a conspicuous row of foramina on the dorsal surface. But more interesting is that the skull roof also exhibits a row of large foramina that seem to be continuous with the previous nasal foramina. CT scans made on the skull corroborates a novel feature within theropods: the nasal foramina on the external surface are linked to an internal canal that runs across the nasal bones. We compared this feature with CT scans of Carnotaurus and revealed that it also possess an internal system as in Skorpiovenator, but being notably smaller. The symmetry and disposition of the foramina in the nasal and skull roof bones of Skorpiovenator would indicate a neurovascular correlate (i.e., blood vessels and nerves), probably to the lateral nasal and supraorbital vessels and the trigeminal nerve. The biological significance of such neurovascular system can be conjectured from several hypotheses. A possible one involves an enhanced blood volume in these bones linked to a zone of thermal exchange, which may help avoid overheat of encephalic tissues. Another plausible hypothesis takes into account the presence of display skin structures in which blood volume nourished the mineralized skin, which would have a role in intraspecific communication. However, other more speculative explanations should not be discarded such as a correlation with integumentary sensory organs.

Carcharodontosauridae theropod tooth crowns from the Upper Cretaceous (Bauru Basin) of Brazil: A reassessment of isolated elements and its implications to palaeobiogeography of the group

Theropod tooth crowns are abundant in the Upper Cretaceous (post-Coniacian) continental deposits of the Bauru Group, Brazil. The distribution of anatomical crown features indicates that a variety of carnivorous dinosaurs inhabited the area at that time, which is consistent with fossil records from other parts of Gondwana. More specifically, some authors have attributed several isolated specimens to the Carcharodontosauridae; while this has important implications for palaeobiogeography and paleoecology, other scholars have argued that the clade became extinct during the Turonian. In this study, we conducted discriminant and phylogenetic analyses for 18 crowns putatively assigned to the Carcharodontosauridae. In short, the discriminant analysis suggested that the specimens should be tentatively assigned to the following groups: non-abelisauroid Ceratosauria, Abelisauridae, Neovenatoridae, Dromaeosauridae, and Pantyrannosauria. By contrast, the phylogenetic analysis indicated that all should be assigned to abelisaurid theropods, which is consistent with the theropod osteological records in both Brazil and Argentina. We recommend using a combined approach involving morphometric and phylogenetic tools when identifying isolated teeth, as this may yield more reliable identifications. We also suggest that all previous reports on the presence of post-Turonian carcharodontosaurids in the Bauru Group are invalid, which also corroborates previous work. Our results indicate that abelisaurids from the Bauru Basin were diverse in morphology and activity; that is, many were quite large and/or played important ecological roles. Findings also support the hypothesis that this taxon had a preference for semi-arid environments.

Footprints of large theropod dinosaurs in the Middle–UpperJurassic (lower Callovian–lower Tithonian) Walloon Coal Measures of southern Queensland, Australia

ABSTRACT Dinosaur tracks associated with coal-mines of the Middle to Upper Jurassic (Callovian–Tithonian) Walloon Coal Measures (Clarence–Morton Basin) have been reported on more than any other track-bearing formation in Australia, yet due to the brevity of ichnological information, remain poorly known. All these tracks were found in sediments directly above coal seams in the ceilings of subterranean mines. This style of mining ceased more than a quarter of a century ago, and with many of the original mines having been back-filled or closed, ichnological investigations are restricted to the study of museum specimens and archival photographs. Here, we consolidate data from the literature, present previously unpublished archival photographs, and show the 3D topography of all accessioned track specimens from the Walloon Coal Measures. We recognise eleven track-bearing sites, most of which produced large (length of 30–50 cm) and very large (length greater than 50 cm) sized theropod tracks, including Australia’s largest carnivorous dinosaur footprint (79 cm long). The domination of theropod tracks is unique among Australian dinosaur tracksites. In light of the absence of near coveal body-fossil candidates, the Walloon Coal Measures ichnofaunal assemblages fills significant gaps in our understanding of Australia's Jurassic dinosaur fauna.

A Carcharodontosaurid tooth from the Hasandong Formation (Lower Cretaceous) of South Korea

A large tooth of theropod dinosaur that was recovered from the Hasandong Formation (Lower Cretaceous; Aptian-Albian) in Daedo island, Hadong Couty, South Gyeongsang Province of South Korea is redescribed. Although the tooth was misidentified as a "Prodeinodon"-like megalosaurid theropod at the first time, detailed comparisons with known theropod dentition anatomy strongly indicate that this tooth belongs to an Acrocanthosaurus-like basal carcharodontosaurid theropod. This referral is supported by its combination of large size, ovoid-shaped cervix outline, mesial carina that does not reach the cervix, labially displaced distal carina and large number of denticles. This tooth is different from other carcharodontosaurid teeth from the same formation in several anatomical aspects (e.g., smaller overall size, presence of transverse lines adjacent to the distal carina, presence of interdenticular sulci in distal carina, denticle densities, crown basal ratio), indicating that carcharodontosaurid diversity in the Early Cretaceous of Korea could have been higher, although these differences may represent positional or individual variations. The presence of Acrocanthosaurus-like theropod teeth (e.g., "Prodeinodon", "Wakinosaurus") from early Cretaceous deposits (Valanginian-Cenomanian) of South Korea, Japan, Mongolia and China indicates that North American Acrocanthosaurus atokensis possibly represents a form that immigrated from the Asia.