Steven W. Salisbury

The origin of modern crocodyliforms: new evidence from the Cretaceous of Australia

While the crocodyliform lineage extends back over 200 million years (Myr) to the Late Triassic, modern forms—members of Eusuchia—do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea. Fossils of non-crocodylian eusuchians are currently rare and, in most instances, fragmentary. Consequently, the transition from Neosuchia to Crocodylia has been one of the most poorly understood areas of crocodyliform evolution. Here we describe a new crocodyliform from the mid-Cretaceous (98–95 Myr ago; Albian–Cenomanian) Winton Formation of Queensland, Australia, as the most primitive member of Eusuchia. The anatomical changes associated with the emergence of this taxon indicate a pivotal shift in the feeding and locomotor behaviour of crocodyliforms—a shift that may be linked to the subsequent rapid diversification of Eusuchia 20 Myr later during the Late Cretaceous and Early Tertiary. While Laurasia (in particular North America) is the most likely ancestral area for Crocodylia, the biogeographic events associated with the origin of Eusuchia are more complex. Although the fossil evidence is limited, it now seems likely that at least part of the early history of Eusuchia transpired in Gondwana.

A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: evidence for their Gondwanan affinities

It has often been assumed that Australasian Cretaceous dinosaur faunas were for the most part endemic, but with some Laurasian affinities. In this regard, some Australasian dinosaurs have been considered Jurassic relicts, while others were thought to represent typical Laurasian forms or endemic taxa. Furthermore, it has been proposed that some dinosaurian lineages, namely oviraptorosaurians, dromaeosaurids, ornithomimosaurians and protoceratopsians, may have originated in Australia before dispersing to Asia during the Early Cretaceous. Here we provide a detailed review of Cretaceous non-avian dinosaurs from Australia and New Zealand, and compare them with taxa from other Gondwanan landmasses. Our results challenge the traditional view of Australian dinosaur faunas, with the majority of taxa displaying affinities that are concordant with current palaeobiogeographic models of Gondwanan terrestrial vertebrate faunal distribution. We reinterpret putative Australian ‘hypsilophodontids’ as basal ornithopods (some of them probably related to South American forms), and the recently described protoceratopsians are referred to Genasauria indet. and Ornithopoda indet. Among Theropoda, the Australian pigmy ‘Allosaurus’ is referred to the typical Gondwanan clade Abelisauroidea. Similarities are also observed between the enigmatic Australian theropod Rapator, Australovenator and the South American carcharodontosaurian Megaraptor. Timimus and putative oviraptorosaurians are referred to Dromaeosauridae. The present revision demonstrates that Australias non-avian Cretaceous dinosaurian faunas were reminiscent of those found in other, roughly contemporaneous, Gondwanan landmasses, and are suggestive of faunal interchange with these regions via Antarctica.

A Megaraptor-like theropod (Dinosauria: Tetanurae) in Australia: support for faunal exchange across eastern and western Gondwana in the Mid-Cretaceous

The fossil record of Australian dinosaurs in general, and theropods in particular, is extremely sparse. Here we describe an ulna from the Early Cretaceous Eumeralla Formation of Australia that shares unique autapomorphies with the South American theropod Megaraptor. We also present evidence for the spinosauroid affinities of Megaraptor. This ulna represents the first Australian non-avian theropod with unquestionable affinities to taxa from other Gondwanan landmasses, suggesting faunal interchange between eastern and western Gondwana during the Mid-Cretaceous. This evidence counters claims of Laurasian affinities for Early Cretaceous Australian dinosaur faunas, and for the existence of a geographical or climatic barrier isolating Australia from the other Gondwanan continents during this time. The temporal and geographical distribution of Megaraptor and the Eumeralla ulna is also inconsistent with traditional palaeogeographic models for the fragmentation of Gondwana, but compatible with several alternative models positing connections between South America and Antarctica in the Mid-Cretaceous.

Reevaluation of the Lark Quarry dinosaur Tracksite (late Albian–Cenomanian Winton Formation, central-western Queensland, Australia): no longer a stampede?

ABSTRACT The Lark Quarry dinosaur tracksite has previously been recognized as recording the stampede of a mixed herd of dozens of small theropod and ornithopod dinosaurs. A reexamination of trackway material reveals that the small theropodtype tracks, previously assigned to the ichnotaxon Skartopus, can co-occur within individual trackways of the ornithopod-type tracks assigned to Wintonopus. Moreover, in singular deep tracks where the overall surface outline resembles Skartopus, the base of the track can also resemble Wintonopus. Whereas the Wintonopus holotype may reflect the pedal anatomy of a shorttoed or subunguligrade ornithopod trackmaker, the elongate ‘oe’ impressions typically associated with Skartopus (including the holotype) primarily provide information on digit movement through the sediment and, in many instances, may represent swim traces. The morphological differences between the two ichnotaxa are therefore not taxonomically significant and we formally propose that Skartopus australis should be considered a junior synonym of Wintonopus latomorum. Longitudinal depth profiles through tracks indicate that many are swim traces. The sedimentology and lithology of Lark Quarry further indicates the site represents a time-averaged assemblage formed in a fluvial-dominated floodplain under variable subaqueous conditions, with the parallel orientation of the numerous trackways formed by trackmakers under the influence of downstream current flow. This indicates that the fluvial environment may have been a preferred route for hydrophilic bipedal dinosaurs. We thus do not consider the Lark Quarry dinosaur tracksite to represent a ‘stampede.’ Instead, the tracksite may represent part of a riverine setting, where the water was shallow, in which small dinosaurs swam and/or waded.

Cranial osteology of the ankylosaurian dinosaur formerly known as Minmi sp. (Ornithischia: Thyreophora) from the Lower Cretaceous Allaru Mudstone of Richmond, Queensland, Australia

Minmi is the only known genus of ankylosaurian dinosaur from Australia. Seven specimens are known, all from the Lower Cretaceous of Queensland. Only two of these have been described in any detail: the holotype specimen Minmi paravertebra from the Bungil Formation near Roma, and a near complete skeleton from the Allaru Mudstone on Marathon Station near Richmond, preliminarily referred to a possible new species of Minmi. The Marathon specimen represents one of the world’s most complete ankylosaurian skeletons and the best-preserved dinosaurian fossil from eastern Gondwana. Moreover, among ankylosaurians, its skull is one of only a few in which the majority of sutures have not been obliterated by dermal ossifications or surface remodelling. Recent preparation of the Marathon specimen has revealed new details of the palate and narial regions, permitting a comprehensive description and thus providing new insights cranial osteology of a basal ankylosaurian. The skull has also undergone computed tomography, digital segmentation and 3D computer visualisation enabling the reconstruction of its nasal cavity and endocranium. The airways of the Marathon specimen are more complicated than non-ankylosaurian dinosaurs but less so than derived ankylosaurians. The cranial (brain) endocast is superficially similar to those of other ankylosaurians but is strongly divergent in many important respects. The inner ear is extremely large and unlike that of any dinosaur yet known. Based on a high number of diagnostic differences between the skull of the Marathon specimen and other ankylosaurians, we consider it prudent to assign this specimen to a new genus and species of ankylosaurian. Kunbarrasaurus ieversi gen. et sp. nov. represents the second genus of ankylosaurian from Australia and is characterised by an unusual melange of both primitive and derived characters, shedding new light on the evolution of the ankylosaurian skull.

Common Avian Infection Plagued the Tyrant Dinosaurs

Background Tyrannosaurus rex and other tyrannosaurid fossils often display multiple, smooth-edged full-thickness erosive lesions on the mandible, either unilaterally or bilaterally. The cause of these lesions in the Tyrannosaurus rex specimen FMNH PR2081 (known informally by the name ‘Sue’) has previously been attributed to actinomycosis, a bacterial bone infection, or bite wounds from other tyrannosaurids. Methodology/Principal Findings We conducted an extensive survey of tyrannosaurid specimens and identified ten individuals with full-thickness erosive lesions. These lesions were described, measured and photographed for comparison with one another. We also conducted an extensive survey of related archosaurs for similar lesions. We show here that these lesions are consistent with those caused by an avian parasitic infection called trichomonosis, which causes similar abnormalities on the mandible of modern birds, in particular raptors. Conclusions/Significance This finding represents the first evidence for the ancient evolutionary origin of an avian transmissible disease in non-avian theropod dinosaurs. It also provides a valuable insight into the palaeobiology of these now extinct animals. Based on the frequency with which these lesions occur, we hypothesize that tyrannosaurids were commonly infected by a Trichomonas gallinae-like protozoan. For tyrannosaurid populations, the only non-avian dinosaur group that show trichomonosis-type lesions, it is likely that the disease became endemic and spread as a result of antagonistic intraspecific behavior, consumption of prey infected by a Trichomonas gallinae-like protozoan and possibly even cannibalism. The severity of trichomonosis-related lesions in specimens such as Tyrannosaurus rex FMNH PR2081 and Tyrannosaurus rex MOR 980, strongly suggests that these animals died as a direct result of this disease, mostly likely through starvation.

The Dinosaurian Ichnofauna of the Lower Cretaceous (Valanginian–Barremian) Broome Sandstone of the Walmadany Area (James Price Point), Dampier Peninsula, Western Australia

ABSTRACT Extensive and well-preserved tracksites in the coastally exposed Lower Cretaceous (Valanginian-Barremian) Broome Sandstone of the Dampier Peninsula provide almost the entire fossil record of dinosaurs from the western half of the Australian continent. Tracks near the town of Broome were described in the late 1960s as Megalosauropus broomensis and attributed to a medium-sized theropod trackmaker. Brief reports in the early 1990s suggested the occurrence of at least another nine types of tracks, referable to theropod, sauropod, ornithopod, and thyreophoran trackmakers, at scattered tracksites spread over more than 80 km of coastline north of Broome, potentially representing one of the worlds most diverse dinosaurian ichnofaunas. More recently, it has been proposed that this number could be as high as 16 and that the sites are spread over more than 200 km. However, the only substantial research that has been published on these more recent discoveries is a preliminary study of the sauropod tracks and an account of the ways in which the heavy passage of sauropod trackmakers may have shaped the Dampier Peninsulas Early Cretaceous landscape. With the other types of dinosaurian tracks in the Broome Sandstone remaining undescribed, and the full extent and nature of the Dampier Peninsulas dinosaurian tracksites yet to be adequately addressed, the overall scientific significance of the ichnofauna has remained enigmatic. At the request of the areas Goolarabooloo Traditional Custodians, 400C hours of ichnological survey work was undertaken from 2011 to 2016 on the 25 km stretch of coastline in the Yanijarri-Lurujarri section of the Dampier Peninsula, inclusive of the coastline at Walmadany (James Price Point). Forty-eight discrete dinosaurian tracksites were identified in this area, and thousands of tracks were examined and measured in situ and using three-dimensional photogrammetry. Tracksites were concentrated in three main areas along the coast: Yanijarri in the north, Walmadany in the middle, and Kardilakan-Jajal Buru in the south. Lithofacies analysis revealed 16 repeated facies types that occurred in three distinctive lithofacies associations, indicative of an environmental transgression between the distal fluvial to deltaic portions of a large braid plain, with migrating sand bodies and periodic sheet floods. The main dinosaurian track-bearing horizons seem to have been generated between periodic sheet floods that blanketed the preexisting sand bodies within the braid plain portion of a tidally influenced delta, with much of the original, gently undulating topography now preserved over large expanses of the present day intertidal reef system. Of the tracks examined, 150 could be identified and are assignable to a least eleven and possibly as many as 21 different track types: five different types of theropod tracks, at least six types of sauropod tracks, four types of ornithopod tracks, and six types of thyreophoran tracks. Eleven of these track types can formally be assigned or compared to existing or new ichnotaxa, whereas the remaining ten represent morphotypes that, although distinct, are currently too poorly represented to confidently assign to existing or new ichnotaxa. Among the ichnotaxa that we have recognized, only two (Megalosauropus broomensis and Wintonopus latomorum) belong to existing ichnotaxa, and two compare to existing ichnotaxa but display a suite of morphological features suggesting that they may be distinct in their own right and are therefore placed in open nomenclature. Six of the ichnotaxa that we have identified are new: one theropod ichnotaxon, Yangtzepus clarkei, ichnosp. nov.; one sauropod ichnotaxon, Oobardjidama foulkesi, ichnogen. et ichnosp. nov.; two ornithopod ichnotaxa, Wintonopus middletonae, ichnosp. nov., and Walmadanyichnus hunteri, ichnogen. et ichnosp. nov.; and two thyreophoran ichnotaxa, Garbina roeorum, ichnogen. et ichnosp. nov., and Luluichnus mueckei, ichnogen. et ichnosp. nov. The level of diversity of the main track types is comparable across areas where tracksites are concentrated: Kardilakan-Jajal Buru (12), Walmadany (11), and Yanijarri (10). The overall diversity of the dinosaurian ichnofauna of the Broome Sandstone in the Yanijarri-Lurujarri section of the Dampier Peninsula is unparalleled in Australia, and even globally. In addition to being the primary record of non-avian dinosaurs in the western half of Australia, this ichnofauna provides our only detailed glimpse of Australias dinosaurian fauna during the first half of the Early Cretaceous. It indicates that the general composition of Australias mid-Cretaceous dinosaurian fauna was already in place by the Valanginian-Barremian. Both sauropods and ornithopods were diverse and abundant, and thyreophorans were the only type of quadrupedal ornithischians. Important aspects of the fauna that are not seen in the Australian mid-Cretaceous body fossil record are the presence of stegosaurians, an overall higher diversity of thyreophorans and theropods, and the presence of large-bodied hadrosauroid-like ornithopods and very large-bodied sauropods. In many respects, these differences suggest a holdover from the Late Jurassic, when the majority of dinosaurian clades had a more cosmopolitan distribution prior to the fragmentation of Pangea. Although the record for the Lower Cretaceous of Gondwana is sparse, a similar mix of taxa occurs in the Barremian-lower Aptian La Amarga Formation of Argentina and the Berriasian-Hauterivian Kirkwood Formation of South Africa. The persistence of this fauna across the Jurassic-Cretaceous boundary in South America, Africa, and Australia might be characteristic of Gondwanan dinosaurian faunas more broadly. It suggests that the extinction event that affected Laurasian dinosaurian faunas across the Jurassic-Cretaceous boundary may not have been as extreme in Gondwana, and this difference may have foreshadowed the onset of Laurasian-Eurogondwanan provincialism. The disappearance of stegosaurians and the apparent drop in diversity of theropods by the mid-Cretaceous suggests that, similar to South America, Australia passed through a period of faunal turnover between the Valanginian and Aptian.

Comment on “A Southern Tyrant Reptile”

Benson et al. (Brevia, 26 March 2010, p. 1613) reported on an Australian tyrannosauroid, represented by a pubis from the late Early Cretaceous of Victoria. However, our examination of this specimen reveals that the critical character used for this referral is not present. We contend that the bone likely belongs to a currently recognized group of Australian theropod or another group not currently known.

New anatomical information on Rhoetosaurus brownei Longman, 1926, a gravisaurian sauropodomorph dinosaur from the Middle Jurassic of Queensland, Australia

ABSTRACT Rhoetosaurus brownei is the only known named pre-Cretaceous sauropod from Australia. It is therefore a potentially important taxon for understanding global paleobiogeographic and phylogenetic patterns among early sauropods. Despite its obvious significance, Rhoetosaurus has been too poorly understood to be included in most recent analyses of early sauropod evolution. With this in mind, we evaluated the osteology and phylogeny of undescribed materials of Rhoetosaurus, in order to attempt to close the gap in this understanding. The lower hind limb of Rhoetosaurus highlights a plethora of differences from other sauropods, supporting the distinctiveness of Rhoetosaurus even in the absence of other materials. Some unique traits include prominent crests and sulci on the tibia medially, a narrow metatarsal articular bridge, and pedal claws with an accessory groove or fossa. The pes plesiomorphically retains four claws where most sauropods have three, and bears superficial similarity to that of Shunosaurus. Preliminary cladistic analysis confirms that Rhoetosaurus is a non-neosauropod gravisaurian, although weak support for the most parsimonious topology suggests further findings are required to improve upon incompleteness in the character data. Examination of alternative phylogenetic hypotheses rules out a close relationship between Rhoetosaurus and East Asian Jurassic sauropods, and indicates a closer examination of the potential relationships between Rhoetosaurus and other contemporaneous Middle Jurassic Gondwanan sauropods is necessary.

Paleoclimate of the Late Cretaceous (Cenomanian-Turonian) portion of the Winton Formation, central-western Queensland, Australia: new observations based on CLAMP and bioclimatic analysis

ABSTRACT Although there is an emerging consensus about global climate patterns during the Cretaceous, details about the climate in Australia at this time are poorly resolved, and estimates for terrestrial climate are scarce. Using Climate Leaf Analysis Multivariate Program (CLAMP) and Bioclimatic Analysis (BA) on plant fossils from the mid- to Upper Cretaceous Winton Formation, central-western Queensland, and working within the context of global paleoclimatic reconstructions and the vertebrate fauna from this unit, we have improved the temporal and geographic resolution of Australias Cretaceous climate. During the time that the Cenomanian–Turonian portion of the Winton Formation was deposited, the climate in central-western Queensland was warm, wet, and relatively equable. Frost would have been extremely uncommon, if it occurred at all, and much of the year would have been favorable for plant growth. These results are consistent with both previous isotope records for northern Australia, and the fauna of the Winton Formation, and are in keeping with current reconstructions of global Cretaceous climates.