A Jurassic ceratosaur from China helps clarify avian digital homologies

Xu, Xing; Clark, James M.; Mo, Jinyou; Choiniere, Jonah N.; Forster, Catherine A.; Erickson, Gregory M.; Hone, David W. E.; Sullivan, Corwin; Eberth, David A.; Nesbitt, Sterling J.; Zhao, Qi; Hernandez, R Rene; Jia, Chengkai; Han, Fenglu; Guo, Yu

doi:10.1038/nature08124

Cited by 200 publications

(344 citation statements)

References 32 publications

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“…However, the finding of an abelisaurid some 10 -15 Myr before the effective separation of the continents of the Northern and Southern Hemispheres begs the question why no abelisauroid remains have been recorded from the Jurassic of Laurasia (a recent record of an abelisauroid from the Middle Jurassic of England [17] cannot be substantiated; see the electronic supplementary material). In contrast, other theropod lineages, which arose at approximately the same time, such as 'elaphrosaurs' [31], ceratosaurids [7,9,36] and basal tetanurans [19], achieved a Pangean distribution during this time (see the electronic supplementary material). Interestingly, a similar biogeographic pattern has recently been inferred for other groups of Mesozoic vertebrates, such as basal eusauropods [37], heterodontosaurid ornithischians [38] and mammals [39,40], in which some clades were restricted to southern Gondwana during the Jurassic, whereas other clades had a global distribution.…”

Section: Discussionmentioning

confidence: 99%

A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

2012

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Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates.

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Section: Discussionmentioning

confidence: 99%

A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

2012

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“…This condition differs from that of most coelurosaurs, including Compsognathus, tyrannosauroids (e.g., Guanlong, Tanycolagreus, Tyrannosaurus; Xu et al, 2009;Carpenter et al, 2005;Brochu, 2003), and more crownward forms (e.g., Ornitholestes, Deinonychus, Velociraptor; Carpenter et al, 2005;Ostrom, 1976), in which Metacarpal III. Among megaraptorans, this bone has been solely recorded in Megaraptor.…”

Section: Comparative Anatomymentioning

confidence: 95%

“…In Megaraptor (Calvo et al, 2004) and Australovenator (White et al, 2012) two carpal elements are documented: a diskshaped radiale, and an enlarged distal carpal described as distal carpal 1 by White et al (2012). Because the homology of this bone among theropods is difficult to interpret (e.g., Xu et al, 2006Xu et al, , 2009Xu et al, , 2014, we will informally describe it as a "semilunate carpal", based on its proximally arched profile in dorsal view.…”

Section: Comparative Anatomymentioning

confidence: 99%

Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy

Novas¹,

Rolando²,

Agnolín³

2016

MMV

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General comparisons of the manual elements of megaraptorid theropods are conducted with the aim to enlarge the morphological dataset of phylogenetically useful features within Tetanurae. Distinctive features of Megaraptor are concentrated along the medial side of the manus, with metacarpal I and its corresponding digit being considerably elongated. Manual ungual of digit I is characteristically enlarged in megaraptorids, but it is also transversely compressed resulting in a sharp ventral edge. We recognize two derived characters shared by megaraptorans and coelurosaurs (i.e., proximal end of metacarpal I without a deep and wide groove continuous with the semilunar carpal, and metacarpals I and II long and slender), and one derived trait similar to derived tyrannosauroids (i.e., metacarpal III length <0.75 length of metacarpal II). However, after comparing carpal, metacarpal and phalangeal morphologies, it becomes evident that megaraptorids retained most of the manual features present in Allosaurus. Moreover, Megaraptor and Australovenator are devoid of several manual features that the basal tyrannosauroid Guanlong shares with more derived coelurosaurs (e.g., Deinonychus), thus countering our own previous hypothesis that Megaraptora is well nested within Tyrannosauroidea.

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“…However, Carrano and Sampson (2008) instead argued that this taxon is the most basal ceratosaur, concordant with its stratigraphic position as the oldest unequivocal fossil of Ceratosauria. More recently, the phylogenetic analysis of Xu et al (2009) found Berberosaurus as a more basal theropod, outside the Ceratosauria + Tetanurae clade. If correct, this would prompt a reinterpretation of neoceratosaur origins and early evolution.…”

Section: Early Jurassic Theropods -Fossil Record and Distributionmentioning

confidence: 99%

The origin and early radiation of dinosaurs

Brusatte

Nesbitt

Irmis

et al. 2010

Earth-Science Reviews

242

214

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Dinosaurs were remarkably successful during the Mesozoic and one subgroup, birds, remain an important component of modern ecosystems. Although the extinction of non-avian dinosaurs at the end of the Cretaceous has been the subject of intense debate, comparatively little attention has been given to the origin and early evolution of dinosaurs during the Late Triassic and Early Jurassic, one of the most important evolutionary radiations in earth history. Our understanding of this keystone event has dramatically changed over the past 25 years, thanks to an influx of new fossil discoveries, reinterpretations of long-ignored specimens, and quantitative macroevolutionary analyses that synthesize anatomical and geological data. Here we provide an overview of the first 50 million years of dinosaur history, with a focus on the large-scale patterns that characterize the ascent of dinosaurs from a small, almost marginal group of reptiles in the Late Triassic to the preeminent terrestrial vertebrates of the Jurassic and Cretaceous. We provide both a biological and geological background for early dinosaur history. Dinosaurs are deeply nested among the archosaurian reptiles, diagnosed by only a small number of characters, and are subdivided into a number of major lineages. The first unequivocal dinosaurs are known from the late Carnian of South America, but the presence of their sister group in the Middle Triassic implies that dinosaurs possibly originated much earlier. The three major dinosaur lineages, theropods, sauropodomorphs, and ornithischians, are all known from the Triassic, when continents were joined into the supercontinent Pangaea and global climates were hot and arid. Although many researchers have long suggested that dinosaurs outcompeted other reptile groups during the Triassic, we argue that the ascent of dinosaurs was more of a matter of contingency and opportunism. Dinosaurs were overshadowed in most Late Triassic ecosystems by crocodile-line archosaurs and showed no signs of outcompeting their rivals. Instead, the rise of dinosaurs was a two-stage process, as dinosaurs expanded in taxonomic diversity, morphological disparity, and absolute faunal abundance only after the extinction of most crocodile-line reptiles and other groups.

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A Jurassic ceratosaur from China helps clarify avian digital homologies

Cited by 200 publications

References 32 publications

A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy

The origin and early radiation of dinosaurs

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