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A Giant Coelophysoid (Ceratosauria) Theropod from the Upper Triassic of New Mexico, USA
Abstract and Figures
A partial skeleton of a very large coelophysoid previously described is redescribed and named Gojirasaurus quayi n. g. n. sp. The specimen consists of a tooth, dorsals, ribs, chevron, scapula, pubis, and tibia from an individual estimated to be about 5.5m long making it one of the largest known Triassic theropod. The specimen shares several apomorphies with other ceratosauromorphs, including transverse process that extends the length of the centrum, parapophysis and diapophysis on the transverse process, web of bone connecting the tuberculum and capitulum, and a long and narrow pubis. The specimen was collected from the Cooper Canyon Formation (middle Norian).
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... The postzygapophyses are closely placed together and their articulation facets face ventrolaterally. A hyposphene is absent between the postzygapophyses and, therefore, there is no accessory intervertebral articulation (figure 4f ), contrasting with its presence in the middle-posterior dorsal vertebrae of Eo. murphi (PVSJ 562), M. rhodesiensis [60], G. quayi [61], Cr. ellioti [63], S. woodi [58] and D. wetherilli [64]. The articulation facets of the prezygapophyses face dorsomedially (figure 4e). ...
... By contrast, Eo. murphi and other early neotheropods (e.g. D. wetherilli [64]; G. quayi [61]; Panguraptor lufengensis [67]) have proportionally taller middleposterior dorsal neural spines (ratio > 0.5). The anterior margin of the neural spine is located at the level of the parapophysis (figure 4a,b). ...
... In some other early theropods, the neural spine also extends posteriorly close to or beyond the level of the postzygapophysis, but the posterior margin of the spine is straight (e.g. Eo. murphi: PVSJ 562; G. quayi [61]). The distal margin of the neural spine is not transversely expanded (figure 4e,f ). ...
We describe a new small-bodied coelophysoid theropod dinosaur, Pendraig milnerae gen. et sp. nov, from the Late Triassic fissure fill deposits of Pant-y-ffynnon in southern Wales. The species is represented by the holotype, consisting of an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur, and by two referred specimens, comprising an isolated dorsal vertebra and a partial left ischium. Our phylogenetic analysis recovers P. milnerae as a non-coelophysid coelophysoid theropod, representing the first-named unambiguous theropod from the Triassic of the UK. Recently, it has been suggested that Pant-y-ffynnon and other nearby Late Triassic to Early Jurassic fissure fill faunas might have been subjected to insular dwarfism. To test this hypothesis for P. milnerae , we performed an ancestral state reconstruction analysis of body size in early neotheropods. Although our results indicate that a reduced body size is autapomorphic for P. milnerae , some other coelophysoid taxa show a similar size reduction, and there is, therefore, ambiguous evidence to indicate that this species was subjected to dwarfism. Our analyses further indicate that, in contrast with averostran-line neotheropods, which increased in body size during the Triassic, coelophysoids underwent a small body size decrease early in their evolution.
... The relatively large anterior exposure of the posterolateral process and its subquadrangular outline in anterior view in BP/ 1/6215 are similar to Liliensternus liliensterni (MB.R 2175.7.8.1) and to Zupaysaurus rougieri (Ezcurra & Novas, 2007;Ezcurra & Brusatte, 2011;Ezcurra, 2017) and differ from the smaller, more lobate posterolateral processes of Gojirasaurus quayi (Carpenter, 1997), Tachiraptor admiribilis (Langer et al., 2014), Megapnosaurus, Lepidus, Cryolophosaurus and Dilophosaurus wetherilli (Ezcurra, 2017). In BP/1/6215, Liliensternus, Tachiraptor admiribilis (Langer et al., 2014), and likely in Dilophosaurus wetherilli (reconstruction obscures these features slightly; Marsh & Rowe, 2020), the angle of the distal end of the anterolateral process relative to the distal tibia margin exceeds 33°, whereas this angle is less than 25°in Coelophysis bauri, Zupaysaurus rougieri, and Gojirasaurus quayi (Carpenter, 1997). There is no indication of a well-developed 'anterior diagonal tuberosity' on the anteromedial side of the anterolateral process, which is similarly lacking in Powellvenator, Liliensternus, Gojirasaurus and Zupaysaurus and is unlike the prominent tuberosity present in some other early branching neotheropods including Camposaurus arizonensis, Megapnosaurus rhodesiensis, and Coelophysis bauri (Ezcurra, 2017). ...
Theropod dinosaurs likely radiated in the wake of the End-Triassic Extinction, but the early history of their diversification remains obscure. The Elliot Formation (EF) and its lateral equivalents in southern Africa preserves abundant continental Late Triassic and Early Jurassic vertebrate fossils, representing an opportunity to study the early phases of theropod evolution. However, Elliot Formation theropod remains are scarce relative to other dinosaurian groups, and most of the South African record pertains to a single taxon, Megapnosaurus rhodesiensis. We present morphological and osteohistological data on two theropod distal tibiae from South Africa’s upper EF. The two new tibiae are larger than any known specimens of M. rhodesiensis, and they show a fast-growing woven-parallel complex (WPC). One of the specimens bears a line of arrested growth, but neither shows outer circumferential lamellae. These observations suggest that both specimens are immature and distinguishable from M. rhodesiensis based on osteohistology. Comparative anatomical observations, including body mass comparisons, further support this distinction. We cannot rule out an identification for one of our tibiae as Dracovenator regenti, the only other valid EF theropod taxon known from body fossils. Our observations indicate that there is likely at least one additional, relatively large-bodied upper EF theropod species that remains unknown from adequate skeletal material.
... Therefore, the increase in body size reflected in the Stormberg Group track record appears to be gradual, with Eubrontes-sized tracks preserved from the Triassic, but becoming more common and larger in the Jurassic. These observations are consistent with global vertebrate track (e.g., Hunt and Lucas, 2007;Lagnaoui et al., 2012;Bernardi et al., 2018) and body fossil records (e.g., Welles, 1984;Rowe and Gauthier, 1990;Carpenter, 1997;Brusatte et al., 2010;Griffin and Nesbitt, 2019), which collectively suggest that larger theropods (TL of 25 -27 cm; BL of ∼5 m) were present, though rare, in the Late Triassic, gaining prevalence in the Jurassic. ...
The end-Triassic mass extinction events mark a pivotal period in archosaur history, and have been proposed to contribute to the rise and dominance of dinosaurs throughout the Mesozoic. In southern Africa, the Triassic–Jurassic boundary is contained within the richly fossiliferous fluvio-lacustrine-aeolian deposits of the upper Stormberg Group in the main Karoo Basin. Due to an absence of high-resolution radioisotopic age constraints, the exact placement of the boundary remains difficult. The Stormberg Group theropod osteological record is limited to scarce, fragmentary material; therefore, the abundant Norian–Pliensbachian tridactyl tracks attributed to theropods are vital for unraveling theropod dinosaur evolutionary trends in southwestern Gondwana. This study considers over 200 upper Stormberg Group tridactyl tracks assigned to the Kayentapus-Grallator-Anchisauripus-Eubrontes (K-GAE) plexus, to quantify their morphological variation across a time span of ∼35 million years. Our findings show that within the upper Stormberg Group, and across the Triassic–Jurassic boundary, the younger tracks become larger, have a decreased mesaxony and a reduced digit III projection. This reduced emphasis of the medial digit is also observed across the K-GAE plexus, and for the individual ichnotaxa across time in the main Karoo Basin, e.g., Eubrontes tracks become less mesaxonic and have a reduced digit III projection higher up in the stratigraphy. This suggests that these morphological trends are not simply linked to size but may reflect a change in autopod morphology through time, which has implications for pedal functionality. Furthermore, being morphologically distinct from contemporaneous North American K-GAE tracks (e.g., reduced elongation and mesaxony, no correlation between digit divarication angles and size), these southern African footprints warrant further investigation.
... Given this distribution, hypothesizing that larger-bodied, non-averostran neotheropods are present only in Lower Jurassic rocks in the southwestern United States is tempting. However, the supposed increase in the body size of North American theropod dinosaurs after the end-Triassic extinction (e.g., Olsen et al., 2002) now appears to have occurred earlier, during the Late Triassic (Carpenter, 1997;Irmis, 2011;Turner and Nesbitt, 2013;Griffin, 2019;Griffin and Nesbitt, 2019). More derived, non-averostran neotheropods may have been present during the latest Triassic in what is now the southwestern United States, but they are poorly represented by the track record. ...
Theropod dinosaurs are minor components of Late Triassic ecosystems in North America, comprising coelophysoids and various non-neotheropods from the Chinle Formation of Arizona, Utah, Colorado, and New Mexico and the Dockum Group of western Texas. By the Sinemurian (Early Jurassic), the coelophysoid “Syntarsus” kayentakatae and the large-bodied non-averostran neotheropod Dilophosaurus wetherilli from the Kayenta Formation were the dominant terrestrial predators. Theropods are virtually unknown from the intervening Rhaetian–Hettangian Moenave Formation, with the exception of two partial coelophysoid pelves from somewhere within the Dinosaur Canyon Member, which includes the Triassic–Jurassic boundary and end-Triassic mass extinction. Here we describe an anterior trunk vertebra from a non-coelophysoid, non-averostran neotheropod from the uppermost Whitmore Point Member of the Moenave Formation in southwestern Utah, which is Hettangian in age. The vertebra has prominent vertebral laminae and associated pneumatic fossae, and anterior and posterior ‘shoulders’ on the neural spine that are similar to those found in Dilophosaurus wetherilli. This vertebra belongs to a theropod that may be as many as 15 million years older than Dilophosaurus wetherilli from the middle of the Kayenta Formation in Arizona. This theropod is associated with Grallator, Eubrontes, and Characichnos theropod traces made on the shores of the Early Jurassic Lake Whitmore that are abundant in the Whitmore Point Member in southwestern Utah. Its occurrence in the Hettangian roughly coincides with the appearance of Eubrontes tracks in North America, indicating that not all contemporaneous theropod traces were made by coelophysoids.
... Bolet & Evans, 2010;Funston et al., 2016a,b), the elements of the pelvic girdle (e.g. Galton, 1982;Carpenter, 1997;Bolet & Evans, 2010;Bennett, 2014), and the fusion of the sacral vertebrae (e.g. Canudo, Royo-Torres & Cuenca-Bescós, 2008;Fanti et al., 2013;Currie et al., 2016), has been used in many groups to assess maturity; co-ossification of postcranial elements is the third most common method used in our database (18% of all studies; Fig. 2C) and has been used in nearly all major saurian groups (Figs 3, 4, 5, 6). ...
Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life‐history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least‐inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260‐million‐year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. ‘juvenile’, ‘mature’) and provide routes for better clarity and cross‐study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method‐specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, ‘Ontogenetic Assessment’, be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well‐represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well‐constrained, empirically tested methods.
... The only dinosauromorphs identified using unambiguous apomorphies from the Bull Canyon Formation are two theropods. The first, Gojirasaurus quayi Carpenter (1997) was recently re-analyzed and is thought to be a neotheropod (Griffin 2019). The second, NMMNH P-4569, was first hypothesized to be a sauropodomorph (Long and Murry 1995) and later a herrerasaurid , but actually represents a neotheropod (Griffin 2019). ...
Dinosauromorph specimens from Petrified Forest National Park have been recovered from four major collecting efforts since 1982, including the most recent paleontological inventory of new park lands acquired in 2011. Additionally, an emphasis on understanding the stepwise acquisition of character traits along the dinosaurian lineage has helped identify previously collected specimens in museum collections. Here we briefly describe and use apomorphies to identify 32 additional dinosauromorph specimens found at Petrified Forest National Park, bringing the total number of dinosauromorph specimens presently known from the park to 50, a 600% increase since the year 2000. These specimens are all Norian in age and come from the Blue Mesa Member, Sonsela Member, and Petrified Forest Member of the Chinle Formation. These include the proximal end of a tibia that represents the oldest unambiguous dinosaur specimen from the Chinle Formation. We then contextualize these specimens with the dinosauromorph assemblages from the Norian of Utah, Colorado, New Mexico, and Texas, as well as the Carnian and Norian dinosauromorph assemblages from South America, Africa, and Europe. Despite increased sampling we still find no evidence for sauropodomorph and ornithischian dinosaurs in Western North America. An increase in sampling, combined with the use of apomorphies to identify collected specimens, will continue to improve the global dinosauromorph fossil record that can be used to answer questions on biochronology and the evolutionary history of the avian lineage.
... In addition, Tachiraptor admirabilis Langer et al., 2014 and the early ceratosaurian Eoabelisaurus mefi Pol & Rauhut, 2012 were added to improve the sampling of early members of the lineage leading to Averostra and early averostrans, respectively. These specimens/species were scored based on firsthand observations of specimens (casts in the case of Tachiraptor admirabilis: LPRP/USP 0747, cast of IVIC-P-2867, and Gojirasaurus quayi Carpenter, 1997: HMN MB.R. 4232.1, cast of UCM 47221). Five characters were added to this data matrix, character 252 was deactivated and some character formulations, scorings and orderings were modified (rationale for these changes is given in Supporting Information, File S1). ...
Neotheropoda represents the main evolutionary radiation of predatory dinosaurs and its oldest records come from Upper Triassic rocks (c. 219 Mya). The Early Jurassic record of Neotheropoda is taxonomically richer and geographically more widespread than that of the Late Triassic. The Lower Jurassic (upper Hettangian–lower Sinemurian) rocks of central England have yielded three neotheropod specimens that have been assigned to two species within the genus Sarcosaurus, S. woodi (type species) and S. andrewsi. These species have received little attention in discussions of the early evolution of Neotheropoda and recently have been considered as nomina dubia. Here, we provide a detailed redescription of one of these specimens (WARMS G667–690) and reassess the taxonomy and phylogenetic relationships of the genus Sarcosaurus. We propose that the three neotheropod specimens from the Early Jurassic of central England represent a single valid species, S. woodi. The second species of the genus, ‘S. andrewsi’, is a subjective junior synonym of the former. A quantitative phylogenetic analysis of early theropods recovered S. woodi as one of the closest sister-taxa to Averostra and provides new information on the sequence of character state transformations in the lead up to the phylogenetic split between Ceratosauria and Tetanurae.
... INTRODUCTION eropod dinosaurs are an important but rare component in terrestrial faunas from the Triassic of western North America (Nesbitt and others, 2007). Although several taxa have been identi ed from New Mexico, including Coelophysis bauri (Colbert, 1989;Rinehart and others, 2009), Gojirasaurus quayi (Carpenter, 1997), Chindesaurus bryansmalli (Irmis and others, 2007), Tawa hallae (Nesbitt and others, 2009), and Daemonosaurus chauliodus (Sues and others, 2011), the surrounding continental deposits have produced little in the way of dinosaurian body fossils. In contrast, an apomorphy-based study by Nesbitt and others (2007) examined all referred dinosaurs from the Triassic of western North America and found only Caseosaurus crosbyensis (Long and Murry, 1995) present in Texas. ...
Triassic dinosaurs represent relatively rare but important components of terrestrial faunas across Pangea. Whereas this record has been well studied at various locales across the American West, there has been no previous systematic review of Triassic material assigned to Dinosauria from Utah. Here, we critically examine the published body fossil and footprint record of Triassic dinosaurs from Utah and revise their record from the state. In addition, we describe a sacrum from a locality within the Upper Triassic Chinle Formation of southeastern Utah. _is specimen represents the only unambiguous Triassic dinosaur body fossil from Utah. MWC 5627 falls within the range of variation known for sacrum morphology from Coelophysis bauri. Based on a literature review and examination of specimens available to us, we restrict the Triassic Utah dinosaurian record to _eropoda from the Chinle Formation. Preliminary reports of Triassic dinosaurs from other clades and formations in Utah are unsubstantiated.
Dilophosaurus wetherilli was the largest animal known to have lived on land in North America during the Early Jurassic. Despite its charismatic presence in pop culture and dinosaurian phylogenetic analyses, major aspects of the skeletal anatomy, taxonomy, ontogeny, and evolutionary relationships of this dinosaur remain unknown. Skeletons of this species were collected from the middle and lower part of the Kayenta Formation in the Navajo Nation in northern Arizona. Redescription of the holotype, referred, and previously undescribed specimens of Dilophosaurus wetherilli supports the existence of a single species of crested, large-bodied theropod in the Kayenta Formation. The parasagittal nasolacrimal crests are uniquely constructed by a small ridge on the nasal process of the premaxilla, dorsoventrally expanded nasal, and tall lacrimal that includes a posterior process behind the eye. The cervical vertebrae exhibit serial variation within the posterior centrodiapophyseal lamina, which bifurcates and reunites down the neck. Iterative specimen-based phylogenetic analyses result in each of the additional specimens recovered as the sister taxon to the holotype. When all five specimens are included in an analysis, they form a monophyletic clade that supports the monotypy of the genus. Dilophosaurus wetherilli is not recovered as a ceratosaur or coelophysoid, but is instead a non-averostran neotheropod in a grade with other stem-averostrans such as Cryolophosaurus ellioti and Zupaysaurus rougieri. We did not recover a monophyletic ‘Dilophosauridae.’ Instead of being apomorphic for a small clade of early theropods, it is more likely that elaboration of the nasals and lacrimals of stem-averostrans is plesiomorphically present in early ceratosaurs and tetanurans that share those features. Many characters of the axial skeleton of Dilophosaurus wetherilli are derived compared to Late Triassic theropods and may be associated with macropredation and an increase in body size in Theropoda across the Triassic-Jurassic boundary.
Isolated theropod teeth are some of the most common fossils in the dinosaur fossil record and are continually reported in the literature. Recently developed quantitative methods have improved our ability to test the affinities of isolated teeth in a repeatable framework. But in most studies, teeth are diagnosed on qualitative characters. This can be problematic because the distribution of theropod dental characters is still poorly documented, and often restricted to one lineage. To help in the identification of isolated theropod teeth, and to more rigorously evaluate their taxonomic and phylogenetic potential, we evaluated dental features in two ways. We first analyzed the distribution of 34 qualitative dental characters in a broad sample of taxa. Functional properties for each dental feature were included to assess how functional similarity generates homoplasy. We then compiled a quantitative data matrix of 145 dental characters for 97 saurischian taxa. The latter was used to assess the degree of homoplasy of qualitative dental characters, address longstanding questions on the taxonomic and biostratigraphic value of theropod teeth, and explore the major evolutionary trends in the theropod dentition.
In smaller phylogenetic datasets for Theropoda, dental characters exhibit higher levels of homoplasy than non-dental characters, yet they still provide useful grouping information and optimize as local synapomorphies of smaller clades. In broader phylogenetic datasets, the degree of homoplasy displayed by dental and non-dental characters is not significantly different. Dental features on crown ornamentations, enamel texture, and tooth microstructure have significantly less homoplasy than other dental features and can be used to identify many theropod taxa to ‘family’ or ’sub-family’ level, and some taxa to genus or species. These features should, therefore, be a priority for investigations seeking to classify isolated teeth.
Our observations improve the taxonomic utility of theropod teeth and in some cases can help make isolated teeth useful as biostratigraphic markers. This proposed list of dental features in theropods should, therefore, facilitate future studies on the systematic paleontology of isolated teeth.
