Saurischian Research Articles

New archosauromorph remains provide data on the age of a unique Late Triassic assemblage from southern Brazil

The Santa Maria Supersequence, an important stratigraphic unit in the Paraná Basin, yielded a diverse range of Triassic tetrapod assemblages, providing valuable insights into the evolutionary history of southwestern Pangea. This study focuses on the Candelária Sequence of the Santa Maria Supersequence, which includes the Hyperodapedon Assemblage Zone (AZ) and the Riograndia AZ. The Hyperodapedon AZ is characterized by the presence of Hyperodapedon rhynchosaurs alongside a diverse array of other taxa, including dinosaurs, pseudosuchians, and cynodonts. In contrast, the Riograndia AZ preserves mostly small cynodonts, lepidosauromorphs, and sauropodomorph dinosaurs. Whereas biostratigraphic correlations between several localities of the Candelária Sequence have been firmly established, certain sites, like the Niemeyer complex in the Agudo municipality of southern Brazil, present challenges because of their unusual assemblage composition, which result in ambiguous depositional ages. Despite yielding thousands of fossil specimens, the Niemeyer complex lacks index fossils typical of the known Brazilian AZs, making reliable correlation with other sites challenging. This study presents and describes new archosauromorph specimens discovered at the upper portion of the Niemeyer complex. The new materials include a rhynchosaur, a saurischian dinosaur, and a possible silesaurid, which represent the first record of these groups for the site. A phylogenetic analysis of the rhynchosaur material provides insights into its taxonomic affinities, offering valuable data for biostratigraphic comparisons. The new data reinforces an age (early Norian?) that is younger than that of the typical outcrops assigned to the Hyperodapedon AZ. Furthermore, these new specimens contribute to the unique assemblage of the Niemeyer complex, shedding light on its significance within the context of the Santa Maria Supersequence and the broader landscape of southern Brazil during the Triassic Period.

Taphonomy and paleohistology of a dinosaur rib from Marília Formation, Bauru Group, in the state of Minas Gerais, Brazil

The Bauru Group (Campanian–Maastrichtian) has one of the richest fossil records of Cretaceous in South America. All dinosaur fossils from this unit were assigned to Saurischia, most of them poorly preserved. We present the histological and taphonomic analysis of a dinosaur dorsal rib fragment from the Marília Formation in the western state of Minas Gerais. Thin sections were prepared to describe the microstructures of the bone tissue and the fossilization processes involved in preserving the specimen. An elemental analysis was also performed to verify the chemical composition of the fossil and rock matrix. Haversian bone was identified in the rib cortex, and no growth marks or an external fundamental system were found. The rib probably belonged to a saurischian dinosaur because of its plank shape and elliptical cross-section. Hypotheses regarding taphonomic processes were inferred. An extended period of subaerial exposure, followed by high-energy transport, was interpreted due to extensive fractures and signs of abrasion on the outer surface of the bone. Pyrite pseudomorphs (framboids) indicate that the bone was deposited in a reductive environment. After burial, the rapid precipitation of calcite and alkaline stability allowed the preservation of apatite during the recrystallization phase. The manganese hydroxides were deposited on apatite crystals during early diagenesis. We concluded that the fossil rib presented a common taphonomic bias identified among vertebrate fossils of the Bauru Group, which is associated with the exposure of the bones to arid and semiarid climates, their transport into the depositional environments and pedogenetic influence during fossil diagenesis.

An annotated checklist of Australian Mesozoic tetrapods

In 2020, the Australasian palaeontological association Australasian Palaeontologists (AAP) joined the Australian government-supported Australian National Species List (auNSL) initiative to compile the first Australian Fossil National Species List (auFNSL) for the region. The goal is to assemble comprehensive systematic data on all vertebrate, invertebrate and plant fossil taxa described to date, and to present the information both within a continuously updated open-access online framework, and as a series of primary reference articles in AAP’s flagship journal Alcheringa. This paper spearheads these auFNSL Alcheringa publications with an annotated checklist of Australian Mesozoic tetrapods. Complete synonymy, type material, source locality, geological age and bibliographical information are provided for 111 species formally named as of 2022. In addition, chronostratigraphically arranged inventories of all documented Australian Mesozoic tetrapod fossil occurrences are presented with illustrations of significant, exceptionally preserved and/or diagnostic specimens. The most diverse order-level clades include temnospondyl amphibians (34 species), saurischian (13 species) and ornithischian (12 species) dinosaurs (excluding ichnotaxa), and plesiosaurian marine reptiles (11 species). However, numerous other groups collectively span the earliest Triassic (earliest Induan) to Late Cretaceous (late Maastrichtian) and incorporate antecedents of modern Australian lineages, such as chelonioid and chelid turtles and monotreme mammals. Although scarce in comparison to records from other continents, Australia’s Mesozoic tetrapod assemblages are globally important because they constitute higher-palaeolatitude faunas that evince terrestrial and marine ecosystem evolution near the ancient South Pole. The pace of research on these assemblages has also accelerated substantially over the last 20 years, and serves to promote fossil geoheritage as an asset for scientific, cultural and economic development. The auFNSL augments the accessibility and utility of these palaeontological resources and provides a foundation for ongoing exploration into Australia’s unique natural history. Stephen F. Poropat [stephenfporopat@gmail.com], Western Australian Organic and Isotope Geochemistry Centre, School of Earth and Planetary Science, Curtin University, Bentley, Western Australia 6102, Australia, and Australian Age of Dinosaurs Museum of Natural History, Lot 1 Dinosaur Drive, Winton, Queensland 4735, Australia; Phil R. Bell [pbell23@une.edu.au], Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia; Lachlan J. Hart [l.hart@unsw.edu.au], Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences (BEES), University of New South Wales, Kensington, New South Wales 2052, Australia, and Australian Museum Research Institute, 1 William Street, Sydney, New South Wales 2010, Australia; Steven W. Salisbury [s.salisbury@uq.edu.au] School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia; Benjamin P. Kear [benjamin.kear@em.uu.se] The Museum of Evolution, Uppsala University, Norbyvägen 16, Uppsala SE-752 36, Sweden.

The origin of an invasive air sac system in sauropodomorph dinosaurs.

One of the most remarkable features in sauropod dinosaurs relates to their pneumatized skeletons permeated by a bird-like air sac system. Many studies described the late evolution and diversification of this trait in mid to late Mesozoic forms but few focused on the origin of the invasive respiratory diverticula in sauropodomorphs. Fortunately, it is possible to solve this thanks to the boom of new species described in the last decade as well as the broad accessibility of new technologies. Here we analyze the unaysaurid sauropodomorph Macrocollum itaquii from the Late Triassic (early Norian) of southern Brazil using micro-computed tomography. We describe the chronologically oldest and phylogenetically earliest unambiguous evidence of an invasive air sac system in a dinosaur. Surprisingly, this species presented a unique pattern of pneumatization in non-sauropod sauropodomorphs, with pneumatic foramina in posterior cervical and anterior dorsal vertebrae. This suggests that patterns of pneumatization were not cladistically consistent prior to the arrival of Jurassic eusauropods. Additionally, we describe the protocamerae tissue, a new type of pneumatic tissue with properties of both camellae and camerae. This reverts the previous hypothesis which stated that the skeletal pneumatization first evolved into camarae, and derived into delicate trabecular arrangements. This tissue is evidence of thin camellate-like tissue developing into larger chambers. Finally, Macrocollum is an example of the gradual evolution of skeletal tissues responding to the fastly specializing Respiratory System of saurischian dinosaurs.

Ornithischian dinosaurs in Southeast Asia: a review with palaeobiogeographic implications

Ornithischian dinosaurs have been discovered in Thailand, Laos, and Malaysia. These bird-hipped herbivores remain relatively rare by comparison with saurischian dinosaurs. In the Late Jurassic, stegosaurs and basal neornithischians from Thailand showed similarities to Middle-Late Jurassic taxa from China. Ornithischians appeared in the fossil record again during the late Early Cretaceous (Aptian-Albian) of Thailand and Laos. They are represented by non-hadrosaurid iguanodontians and basal ceratopsians. A few specimens have been reported from poorly dated Early Cretaceous rocks of Malaysia. Here, we illustrate the diversity of ornithischian assemblages in Southeast Asia and discuss their palaeobiogeographical implications.

How pneumatic were the presacral vertebrae of dicraeosaurid (Sauropoda: Diplodocoidea) dinosaurs?

Abstract Skeletal pneumaticity implies bone invasion via air sacs that are diverticula of the respiratory system. Among extant vertebrates, this feature is found only in birds, and in extinct taxa it occurs in saurischian dinosaurs and pterosaurs. The sauropod axial skeleton is characterized by having a complex architecture of laminae and fossae that have usually been related to some degree of pneumaticity. We examined the external anatomy of the presacral vertebrae of two dicraeosaurid sauropods holotype specimens, Amargasaurus cazaui and Brachytrachelopan mesai, and obtained computed tomography scan images from mid- and posterior cervical vertebrae of both specimens and an anterior dorsal vertebra of Brachytrachelopan. In all cases, we recognized a ‘procamerate’ internal pneumatization pattern, confirming previous hypotheses that dicraeosaurid vertebral pneumaticity is reduced relative to other eusauropod taxa. Thus, pneumatic diverticula were present in Amargasaurus, Brachytrachelopan, Dicraeosaurus, Pilmatueia and, possibly, other dicraeosaurid sauropods, but these diverticula did not invade their presacral vertebrae extensively. Furthermore, we found that the more pneumatic dicraeosaurid taxa, with some exceptions, occupy a basal position within Dicraeosauridae. There is some variability in pneumaticity among dicraeosaurids from Gondwana, with Pilmatueia achieving the highest degree of pneumatization.

The lost titan of Cauvery

In 1987, authors P. Yadagiri and K. Ayyasami described a giant dinosaur, Bruhathkayosaurus matleyi, from the Late Cretaceous beds of the Cauvery Basin, India. Unfortunately, the fossil remains of this giant had disintegrated into dust before they reached the repository, making B. matleyi a dubious species. Gigantism is one of the many characteristic features of dinosaurs that grab public attention, and there is much fossil evidence that suggests gigantism was not limited to any specific group of dinosaurs. Nevertheless, this characteristic feature was very advanced and extensive among sauropod dinosaurs, which belonged to a group of long necked herbivorous dinosaurs. Sauropods evolved from basal saurischian dinosaurs about 200 Ma and survived until the K/Pg (Cretaceous–Palaeogene) mass extinction event, about 66 Ma. By the Late Jurassic period, many colossal size sauropods had evolved, such as Supersaurus, Diplodocus, Barosaurus, etc. but together with other Diplodocidae, they went extinct by the end of the Late Jurassic. During the Cretaceous, a new clade of sauropod dinosaurs evolved, the Titanosauria. The Titanosauria diversified into various genera, and in terms of size, they ranged from a 6‐m‐long Magyarosaurus, to the 35‐m‐long Argentinosaurus. Most of these giant titanosaurs, including Argentinosaurus, alongside Patagotitan, Dreadnoughtus, Puertasaurus, and Futalognkosaurus, are known from South America, making this continent truly a ‘land of giants’ during the Cretaceous. However, the latest discoveries of this group indicate that supersized titanosaurs were not just restricted to South America, with Paralititan from Africa and Australotitan from Australia. Loss of the fossil remains of B. matleyi has raised not only questions upon the validity of the species, but also questions the notion that any supersized dinosaur lived in India. Here we critically review pieces of evidence in support of supersize dinosaur remains from Southern India.

NUEVOS RESTOS DE REBAQUISÁURIDOS DESDE LA FORMACIÓN HUINCUL (CENOMANIANO MEDIO–TURONIANO TEMPRANO) DEL CENTRO DE LA CUENCA NEUQUINA, PATAGONIA, ARGENTINA

In the central Neuquén Basin, the Huincul Formation comprises thick successions of Upper Cretaceous fluvial deposits widely exposed at the south and north-west of Huincul High. The vertebrate fossil record from the Huincul Formation is very abundant, especially considering the saurischian dinosaurs, including several theropod (Mapusaurus, Taurovenator, Aoniraptor, Skorpiovenator, Ilokelesia, Gualicho, Overoraptor, Tralkasaurus, and Huinculsaurus) and sauropod specimens (Choconsaurus, Argentinosaurus, Cathartesaura, Limaysaurus, and the indeterminate rebbachisaurid MMCH-Pv-49). In this contribution, we describe new rebbachisaurid sauropod findings from the El Orejano locality (Neuquén Province, Argentina), where coarse sandstones outcrop referred to the lower section of the Huincul Formation. The new material includes three axial elements that we refer to Rebbachisauridae: a partial dorsal neural arch (MAU-Pv-EO-633), an incomplete dorsal vertebra (MAU-Pv-EO-634), and an almost complete caudal vertebra (MAU-Pv-EO-666). These new findings share different features with other members of that family, although show some morphological differences with other rebbachisaurid taxa, which suggest a more diversified fauna in the central Neuquén Basin than previously known, at least during the Cenomanian/Turonian interval. This record from the new fossiliferous locality of El Orejano allows us to improve our knowledge about the morphological diversity of the Rebbachisauridae during the early Late Cretaceous. Furthermore, it represents one of the most modern records of the family, adding new information on the last stages of the evolutionary history of rebbachisaurids.

Paleontology

Paleontology Alyssa Pelish (bio) The excavation of Patagotitan mayorum, the largest dinosaur ever uncovered, took over eighteen months. The video that plays on a loop at the Museum of Natural History shows a swarm of paleontologists going at the pale red rock like workers in a quarry. They wield shovels and pickaxes and jack hammers and chisels. Some kind of crane-like machine, with blunt teeth, heaves mouthfuls of rock up from the site. One man uses a push broom to sweep debris from an enormous femur. Bulldozers are brought in to clear a road through the rocky, scrubby barrens of the Patagonian Desert to carry the bones off the site. In the lab, beneath the light of a magnifying lens, men apply what look like dental instruments—tiny drills, or maybe cleaning devices—to the fossilized bones. In the lab, notes the outback-voiced narrator, any remaining fragments of rock are chipped away. I like to think about this as I sit staring into the hull of the Patagotitan’s rib cage. Some 223 different sauropod bones were exhumed from layers and layers of sediment, the mudstone and sandstone chipped away from them, the dust brushed off. Eighty-four of the bones could be pieced together to form the titanic skeleton that rises as high as forty-six feet and extends for 120. I like to think about this. I don’t know, though, what Miles is thinking when he sits here on this black bench that, in the dim light, is almost invisible against the equally black wall striped with the shadows of the Patagotitan’s enormous ribs. He will sit here and stare for a while, sometimes a quarter of an hour, hunching his small body in the inexplicable cold of the room, his soft face solemn and close-lipped. Miles and I come here, to the museum, on Fridays. It’s marginally less crowded in the late afternoon of a weekday, after I’ve picked him up from preschool. He and I always enter the museum from the subway, which makes the whole trip seem somewhat covert, as if we are secret agents who must avoid the exposure of the streets. Miles and I step from the subway not out into the light of day and the enlightenment of knowledge promised on the Teddy Roosevelt memorial facade, but into the windowless basement of the museum and, then, by stepping into the vacuum tube of an elevator, toward the dinosaur bones. He and I sometimes visit the other halls, the other floors. The Hall of Reptiles and Amphibians on the third, Birds of the World on the second, North American Forests on the first. But we always drift back to the dinosaurs. Most days, that is the only place we go. Miles doesn’t say what it is he likes about the dinosaur bones. Is it the overwhelming scale of the big ones, the spookiness of their skeletal silhouettes, their [End Page 30] faint resemblance to the familiar characters in his picture books? Is it their silence? Miles has never quite stuck by my side in the museum. Even when I first brought him here, he wandered the saurischian and ornithischian halls on his own, and I followed at a tentative distance, like a one-person surveillance team. We enter the museum together—he knows he needs me to flash our members’ pass. We ride the elevator to the fourth floor together. We exit the elevator together, both of us turning right. But Miles enters the Hall of Saurischian Dinosaurs on his own, beneath the silent flock of seagulls suspended above. He might pause at the glass-encased skeleton of the Diatryma gigantea, a flamingo-like creature posed in profile, or at the gigantic skull of a T. rex, its hollows poured full of what looks like concrete. I follow, at a distance, careful not to appear obvious about it. Mostly, he seems indifferent to my presence, but if I get too close, make a conversational foray, his shoulders tighten and he soon wanders, silently, away, and I feel like a clumsy spy who has just been made. When we began coming here, I at first...

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

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

The largest theropod track site in Yunnan, China: a footprint assemblage from the Lower Jurassic Fengjiahe Formation.

Yunnan Province is famous for its diversified Lufeng vertebrate faunas containing many saurischian dinosaur remains. In addition to the body fossil record, dinosaur ichnofossils have also been discovered in Yunnan, and the number of published track sites is on the rise. We report a theropod assemblage from the Lower Jurassic Fengjiahe Formation in Xiyang, central Yunnan. It is the third report and description of dinosaur footprints from the Fengjiahe Formation, and this new track site is the largest in number of footprints for theropods in Yunnan. Over one hundred footprints are preserved on different layers of a claystone-dominated succession close to the Lower-Middle Jurassic boundary. The track area is referred to as a lacustrine shallow-water paleoenvironment. Tracks vary in size, morphology, and preservation. All are tridactyl and digitigrade, and some are identified as undertracks. The best preserved footprints were divided into three morphotypes: morphotype A (>8 cm–<21 cm) resembling Grallator; morphotype B (>27 cm–<30 cm) identified as Kayentapus xiaohebaensis; and morphotype C, an isolated footprint (39 cm) referred to the ichnogenus Kayentapus. Although footprint shape is influenced by many factors, biotic or abiotic, morphological differences among tracks such as size, divarication angles and proportions imply that at least three different kinds of theropods were visiting this site frequently. Theropod body fossils found in the surrounding area, such as Sinosaurus, turn out to be similar in body size to the projected size estimated from footprint lengths at the track site. In Yunnan, discoveries of theropod body fossils are rare. In that respect, the track record is a useful diversity indicator which can help to encompass theropod diversity patterns. Broadly speaking, large predators (five meters long or more) were uncommon in Early Jurassic ecosystems. Accordingly, large tracks are scarce on the track site, but not absent. Trackmakers of all sizes presumably coexisted in this tropical Jurassic ecosystem, and were regularly drawn to the track site in search of water or food resources.

Dinosaur Eggs and Babies in the UNESCO GGN Hateg Country Dinosaurs Geopark (Romania)

In 1898, when the first dinosaur eggs were discovered in Hațeg Country (which in 2005 became part of the UNESCO Global Geopark Network), not one dinosaur egg had ever been unearthed either in the vicinity or anywhere in Romania. Twenty years later, tens of sites bearing remnants of dinosaur eggs – of which at least eight are dinosaur incubation sites – had been mapped in Hațeg Country and across Southern Transylvania as a whole. The most famous is the site at Tuștea, situated in the north-western part of the Hațeg Basin, especially well known because of the so-called “Tuștea Puzzle” whereby spherical megaloolithid eggs, almost universally seen as those of titanosaurid sauropods, are associated with hadrosaurid neonates. Tuștea is the only site in Europe to feature the remains of dinosaur neonates alongside eggs and eggshells from the Upper Cretaceous. Research here and in other areas of the Hațeg Basin highlighted the climates and sedimentology of the areas where the eggs were laid roughly 68–70 million years ago, and revealed aspects of nest building and the behavior of dinosaur neonates after hatching. The site’s scientific importance is strengthened by the great diversity of vertebrate fossil discoveries: frogs, lizards, snakes, saurischian and ornithischian dinosaurs, pterosaurs and mammals – 21 taxa in total, ranking Tuștea among the richest paleontological sites in Europe. After 24 years of continuous research primarily by professors and students from the University of Bucharest, the current owner of the land, making use of legislative inconsistencies governing the right to land ownership, forbade further investigation. During this time, the research site has degraded substantially and today requires urgent restorative and conservation measures lest it be lost forever.

Vertebral pneumaticity of the paravian theropod Unenlagia comahuensis, from the Upper Cretaceous of Patagonia, Argentina

Postcranial skeletal pneumaticity (PSP) characterizes extant birds. This feature is related to a series of air sacs connected to the lungs and prolonged in diverticula that invade bones internally. Previous works revealed that PSP was present along the line to birds, being distinctive of pterosaurs and saurischian dinosaurs. PSP is profuse in the vertebral column of sauropods and theropods and was very studied in sauropods, although scarcely in non-avian theropods. Here we analyze the vertebral pneumaticity of the unenlagiine theropod Unenlagia comahuensis, including the observation through CT scans. Unenlagiinae is a clade of southern dromaeosaurid theropods that is closely related to birds. The vertebral centra have lateral pneumatic foramina (lpf) within fossae (commonly termed ‘pleurocoels’) in middle and posterior dorsals, an unusual feature among extant birds and many non-avian theropods. Another possibly pneumatic fossa stands out at both sides of the neural spine base, which is not present in dorsals of other non-avian theropods, except the unenlagiine Unenlagia paynemili. CT scans revealed camellate tissue in the centra, consisting of small chambers separated by thin trabeculae. Camellae are also observed in the unenlagiines U. paynemili and Austroraptor cabazai, other dromaeosaurids, other coelurosaurs, and some non-coelurosaurian tetanurans. Instead, more primitive groups generally have camerae (larger chambers separated by scarce thick septa). Thus, a possible trend of the vertebral inner pneumaticity types is observed throughout non-avian theropod evolution, as indicated by previous authors. This study provides valuable information that helps to clarify this trend, not only in dromaeosaurids but also throughout theropod evolution.

New dinosaur, crocodylomorph and swim tracks from the Late Jurassic of the Lusitanian Basin: implications for ichnodiversity

New dinosaur (theropod and sauropod), crocodylomorph and swim tracks from Upper Jurassic units of the Lusitanian Basin, housed at the Sociedade de História Natural in Torres Vedras, are here described. They were collected from three different geological formations, the Praia da Amoreira-Porto Novo (upper Kimmeridgian) and the Alcobaça (Kimmeridgian-lower Tithonian) formations in the Consolação Sub-basin and the Freixial Fm. (middle-upper Tithonian) in the Turcifal Sub-basin. Four different theropod morphotypes are identified as follows: cf. Jurabrontes isp., Megalosauripus cf. transjuranicus, Grallatoridae indet. and an indeterminate morphotype (Theropoda indet.) that have affinities with other Therangospodus-like tracks described in Europe. An indeterminate sauropod track is also identified. These five morphotypes suggest high saurischian dinosaur ichnodiversity, similar to that seen in other European Late Jurassic areas (e.g. the Swiss Jura Mountains), but represent just a portion of the higher diversity exhibited by the osteological record in the Lusitanian Basin. Further, one crocodylomorph pes track identified as Crocodylopodus isp. and swim tracks assigned to Characichnos isp., possibly also produced by crocodylomorphs, are also identified. The newly identified ichnotaxa, together with the older and other recent identifications, indicate ichnodiversity comparable with the richest coeval Upper Jurassic units.

A new species of early-diverging Sauropodiformes from the Lower Jurassic Fengjiahe Formation of Yunnan Province, China

Sauropodomorpha were herbivorous saurischian dinosaurs that incorporate Sauropoda and early-diverging sauropodomorphs. The oldest sauropodomorph remains are known from Late Triassic deposits, most of them Gondwanan. The Laurasian record comprises some Triassic forms, but the bulk is Jurassic in age. Among the 14 Jurassic non-sauropodan sauropodomorphs from Laurasia described in the past, 8 are from China. Here we describe a new non-sauropodan sauropodomorph, Irisosaurus yimenensis gen. et sp. nov., from the Early Jurassic Fengjiahe Formation of China. Nearly all of the non-sauropodan sauropodomorph genera currently known from China were first reported from the Lufeng Formation. The Fengjiahe Formation is its Southern equivalent, bringing a fauna similar to that of the Lufeng Formation to light. The new genus is defined based on an incomplete but unique maxilla, with a premaxillary ramus higher than long prior to the nasal process, a large and deep neurovascular foramen within the perinarial fossa, and a deep perinarial fossa defined by a sharp rim. Phylogenetic analysis places Irisosaurus at the very base of Sauropodiformes, as the sister-taxon of the Argentinean genus Mussaurus. This specimen adds to a growing assemblage of Chinese Jurassic non-sauropodan sauropodomorphs that offers new insight into the Laurasian evolution of this clade.

More than one way to be a giant: Convergence and disparity in the hip joints of saurischian dinosaurs

Saurischian dinosaurs evolved seven orders of magnitude in body mass, as well as a wide diversity of hip joint morphology and locomotor postures. The very largest saurischians possess incongruent bony hip joints, suggesting that large volumes of soft tissues mediated hip articulation. To understand the evolutionary trends and functional relationships between body size and hip anatomy of saurischians, we tested the relationships among discrete and continuous morphological characters using phylogenetically corrected regression. Giant theropods and sauropods convergently evolved highly cartilaginous hip joints by reducing supraacetabular ossifications, a condition unlike that in early dinosauromorphs. However, transitions in femoral and acetabular soft tissues indicate that large sauropods and theropods built their hip joints in fundamentally different ways. In sauropods, the femoral head possesses irregularly rugose subchondral surfaces for thick hyaline cartilage. Hip articulation was achieved primarily using the highly cartilaginous femoral head and the supraacetabular labrum on the acetabular ceiling. In contrast, theropods covered their femoral head and neck with thinner hyaline cartilage and maintained extensive articulation between the fibrocartilaginous femoral neck and the antitrochanter. These findings suggest that the hip joints of giant sauropods were built to sustain large compressive loads, whereas those of giant theropods experienced compression and shear forces.

Modeling Dragons: Using linked mechanistic physiological and microclimate models to explore environmental, physiological, and morphological constraints on the early evolution of dinosaurs.

We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate the metabolic function of the Late Triassic dinosaurs Plateosaurus and Coelophysis during global greenhouse conditions. We tested a variety of assumptions about resting metabolic rate, each evaluated within six microclimate models that bound paleoenvironmental conditions at 12° N paleolatitude, as determined by sedimentological and isotopic proxies for climate within the Chinle Formation of the southwestern United States. Sensitivity testing of metabolic variables and simulated "metabolic chamber" analyses support elevated "ratite-like" metabolic rates and intermediate "monotreme-like" core temperature ranges in these species of early saurischian dinosaur. Our results suggest small theropods may have needed partial to full epidermal insulation in temperate environments, while fully grown prosauropods would have likely been heat stressed in open, hot environments and should have been restricted to cooler microclimates such as dense forests or higher latitudes and elevations. This is in agreement with the Late Triassic fossil record and may have contributed to the latitudinal gap in the Triassic prosauropod record.

On the taxonomic status of Teyuwasu barberenai Kischlat, 1999 (Archosauria: Dinosauriformes), a challenging taxon from the Upper Triassic of southern Brazil.

The controversial dinosauriform Teyuwasu barberenai Kischlat, 1999 (Fig. 1B) is based on a right femur (BSPG AS XXV 53) and tibia (BSPG AS XXV 54), formerly referred to the pseudosuchian 'Hoplitosuchus raui' (= Hoplitosaurus raui) Huene, 1938 (see also Huene, 1942). This material comes from a classic Late Triassic (Carnian) locality in southern Brazil (Fig. 1A), the Cerro da Alemoa outcrop on the Alemoa complex, that has yielded several noteworthy tetrapod specimens (see Garcia et al., 2019, for a complete list of references). When reviewing these abovementioned materials, Kischlat (1999) considered it to belong to a "robust saurischian dinosaur", but later this taxon was considered to be a nomen dubium (Langer et al., 2010; Ezcurra, 2012). Foremost, the initial description of this taxon is problematic, because Kischlat (1999) presented it in a symposium abstract which does not constitute a published work [which is not allowed under the Art. 9.10 of the International Commission on Zoological Nomenclature (ICZN)]. Moreover, the author did not list traits that clearly differentiated Teyuwasu from other coeval dinosauriforms (cf. Art. 13 of the ICZN, see further below). In particular, it was not adequately distinguished from Staurikosaurus pricei Colbert, 1970 (Fig. 1B), which also comes from the same Alemoa complex, but from another nearby outcrop (Sanga Grande/Sanga de Baixo) considered equivalent in stratigraphic level and horizon with the lower levels of the Cerro da Alemoa site (Huene, 1942; Colbert, 1970; see also Garcia et al., 2019) (Fig. 1A). However, Huene (1942) did not clearly specify that the materials (femur and tibia) later assembled by Kischlat (1999) into the holotype of Teyuwasu were found in close association, although Huene (1942) cited that they come from the same stratigraphical level and horizon, and to our interpretation, their morphology and preservational features are compatible. Still, assigning these bones as part of a single individual is tentative.

Taphonomic analysis of saurischian dinosaurs from the Plottier Formation (Upper Cretaceous), Mendoza, Argentina

The uppermost Cretaceous continental deposits of the Neuquén Basin (west-central Argentina) have yielded a high diversity vertebrate assemblage, including numerous dinosaur species. The Neuquén Group is the richest unit in remains of dinosaur of the basin and comprises the Río Limay, the Río Neuquén and the Río Colorado subgroups. In this group, there is abundance of isolated, disarticulated or partially articulated sauropods and theropods. However, little is known about the taphonomic history of fossil assemblages. In this study, dinosaur remains from the Plottier Formation (late Coniacian-early Santonian) found in the Cerro Guillermo area in southern Mendoza are examined. The investigation of fossil occurrences within the study area revealed the existence of different taphonomic modes, from isolated bones until partially articulated skeletons preserved in deposits of floodplain and fluvial channel settings. SEM-EDS analysis showed the substitution of hydroxyapatite by francolite in the bone microstructure. The presence of fluorine-in one of the cases-suggested a link between the elemental composition and depositional environments: floodplain and fluvial channel. The survey of the vertebrate accumulation types and their sedimentary context allowed documenting a wide range of processes responsible for their genesis, operating within a meandering fluvial environment. This contribution represents a holistic approach about taphonomic history of Cretaceous dinosaurs for assessing the differential preservation of fossil assemblages in fluvial environments.

Palaeoecological implications of an Upper Cretaceous tetrapod burrow (Bauru Basin; Peirópolis, Minas Gerais, Brazil)

We describe a globally rare example of a tetrapod burrow from the Upper Cretaceous Bauru Group (Bauru Basin) from Peirópolis, Minas Gerais State, Brazil. The sedimentary succession containing the burrow includes a rich vertebrate assemblage comprising fish, podocnemid turtles, mesoeucrocodylians, saurischian dinosaurs, among others. The burrow is composed of an oblique tunnel (~30°), oval in cross-section, with a horizontal and sub-oval terminal chamber; it is 1.3 m long from the midpoint of its inferred entrance to the midpoint of the bottom of the chamber. It occurs in the upper portion of a sandstone succession, interpreted as a braided channel deposit, and the burrow-fill comprises medium-grained sandstone with mudstone intraclasts derived from fluvial floodplain facies. it is overlain by other fluvial channel deposits. Analyses suggest that the burrow was dug after the filling of the braided channel and during the pedogenesis of its exposed upper surface. Based on burrow morphology and size, the most plausible producer of this burrow is a notosuchian mesoeucrocodylian, such as small to mid-sized notosuchians (e.g., sphagesaurids). The Bauru Group has an extensive fossil record of notosuchians with disparate morphologies, and it is noteworthy that the small-sized notosuchian Labidiosuchus amicum comes from the same unit as the burrow. Moreover, arid to semi-arid conditions have been inferred for fossil-bearing rocks of this unit, and as such the data here presented add to our palaeoecological knowledge of Cretaceous mesoeucrocodylians in Gondwana. Moreover, it constitutes a new Cretaceous record of a tetrapod burrow during a period when such ichnofossils are globally rare.