A critical re‐evaluation of the Late Triassic dinosaur taxa of North America

Nesbitt, Sterling J.; Irmis, Randall B.; Parker, William G.

doi:10.1017/s1477201907002040

Cited by 133 publications

(257 citation statements)

References 68 publications

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“…Similarly, Nesbitt et al (2007) demonstrated that several supposed dinosaurs from the Late Triassic of North America actually represent dinosauromorphs, the closest relatives to dinosaurs rather than bona fide members of the group. This historical review, although brief, testifies to both a practical problem in identifying Late Triassic specimens and a remarkable fact about evolution during this period.…”

Section: Taxa Often Mistaken As Dinosaursmentioning

confidence: 98%

“…This is a direct result of the discovery of several close dinosaur relatives, such as Asilisaurus , Silesaurus (Dzik, 2003), Sacisaurus (Ferigolo and Langer, 2007), and Dromomeron (Irmis et al, 2007a;Nesbitt et al, 2009a), as well as the redescription of Marasuchus (Sereno and Arcucci, 1994b), Lagerpeton (Sereno and Arcucci, 1994a), and Eucoelophysis (Ezcurra, 2006;Nesbitt et al, 2007). These characters include: ectopterygoid dorsal to transverse flange of the pterygoid; posteroventrally oriented glenoid on the scapula and coracoid; reduced pubis/ischium contact; reduced ischiadic medioventral lamina; inturned femoral head; proximal femur with reduced medial tuberosity; anterior trochanter of the femur present; tibial descending process that fits posterior to the astragalar ascending process; flat to concave proximal calcaneum; presence of mesotarsal ankle; metatarsals II and IV subequal in length; and a distal end of metatarsal IV that is taller than wide.…”

Section: Character States That Clearly Do Not Diagnose Dinosauriamentioning

confidence: 99%

“…Chindesaurus bryansmalli and Guaibasaurus candelariensis are two other enigmatic saurischian dinosaurs from the Late Triassic. Chindesaurus is from the Upper Triassic (Norian) Chinle Formation of Arizona (Long and Murry, 1995;Nesbitt et al, 2007). It reached lengths of 2-3 m, and is mainly known from the incomplete skeleton of the holotype specimen, which preserves a partial vertebral column, pelvis, and hindlimbs.…”

Section: Ambiguous Taxa: Eoraptor and Herrerasauridaementioning

confidence: 99%

“…Although hundreds of skeletons of Coelophysis are known from Ghost Ranch, theropods are generally rare components of other Late Triassic ecosystems (e.g., Rauhut and Hungerbühler, 2000;Nesbitt et al, 2007). Carnivorous theropods are much rarer (in an absolute faunal abundance sense) and less diverse (in a taxonomic sense) than contemporary carnivorous crurotarsans such as phytosaurs, ornithosuchids, and rauisuchians (e.g., Welles, 1986).…”

Section: Late Triassic Theropods -Paleobiologymentioning

confidence: 99%

“…Reanalysis of existing specimens has improved our understanding of character evolution on the lineage leading to Dinosauria (e.g., Sereno and Arcucci, 1994a,b;Langer and Benton, 2006;Brusatte et al, 2010b) and has changed our understanding of the distribution of early dinosaurs in time and space (Parker et al, 2005;Irmis et al, 2007b;Nesbitt et al, 2007). Most recently, quantitative analyses, which take into account this avalanche of new morphological and geological data, have examined in unprecedented detail the macroevolutionary, biogeographical, and paleoecological changes associated with the rise of dinosaurs (e.g., Brusatte et al, 2008a,b;Nesbitt et al, 2009bNesbitt et al, , 2010.…”

Section: Introductionmentioning

confidence: 99%

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The origin and early radiation of dinosaurs

Brusatte

Nesbitt

Irmis

et al. 2010

Earth-Science Reviews

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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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Section: Taxa Often Mistaken As Dinosaursmentioning

confidence: 98%

Section: Character States That Clearly Do Not Diagnose Dinosauriamentioning

confidence: 99%

Section: Ambiguous Taxa: Eoraptor and Herrerasauridaementioning

confidence: 99%

Section: Late Triassic Theropods -Paleobiologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The origin and early radiation of dinosaurs

Brusatte

Nesbitt

Irmis

et al. 2010

Earth-Science Reviews

Self Cite

243

214

View full text Add to dashboard Cite

show abstract

References

2012

Dinosaur Paleobiology

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Pedal Proportions of Poposaurus gracilis: Convergence and Divergence in the Feet of Archosaurs

Farlow

Schachner

Sarrazin

et al. 2014

The Anatomical Record

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The crocodile-line basal suchian Poposaurus gracilis had body proportions suggesting that it was an erect, bipedal form like many dinosaurs, prompting questions of whether its pedal proportions, and the shape of its footprint, would likewise "mimic" those of bipedal dinosaurs. We addressed these questions through a comparison of phalangeal, digital, and metatarsal proportions of Poposaurus with those of extinct and extant crocodileline archosaurs, obligate or facultatively bipedal non-avian dinosaurs, and ground birds of several clades, as well as a comparison of the footprint reconstructed from the foot skeleton of Poposaurus with known early Mesozoic archosaurian ichnotaxa. Bivariate and multivariate analyses of phalangeal and digital dimensions showed numerous instances of convergence in pedal morphology among disparate archosaurian clades. Overall, the foot of Poposaurus is indeed more like that of bipedal dinosaurs than other archosaur groups, but is not exactly like the foot of any particular bipedal dinosaur clade. Poposaurus likely had a digitigrade stance, and its footprint shape could have resembled grallatorid ichnotaxa, unless digit I of the foot of Poposaurus commonly left an impression. Anat Rec, 297:1022Rec, 297: -1046Rec, 297: , 2014. V C 2014 Wiley Periodicals, Inc.Key words: Poposaurus; archosaur pedal morphology; vertebrate ichnologyThe early Mesozoic adaptive radiation of archosaurs produced a diversity of reptilian life forms; these animals were variously large or small; aquatic, terrestrial, or aerial; herbivorous or carnivorous; ponderous or cursorial (Ewer,

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A critical re‐evaluation of the Late Triassic dinosaur taxa of North America

Cited by 133 publications

References 68 publications

The origin and early radiation of dinosaurs

The origin and early radiation of dinosaurs

References

Pedal Proportions of Poposaurus gracilis: Convergence and Divergence in the Feet of Archosaurs

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