Preliminary palynological zonation of the Chinle formation, southwestern U.S.A., and its correlation to the Newark supergroup (eastern U.S.A.)

Litwin, Ronald J.; Traverse, Alfred; Ash, Sidney R.

doi:10.1016/0034-6667(91)90028-2

Cited by 96 publications

(70 citation statements)

References 19 publications

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“…Dromomeron romeri Irmis et al, 2007b AGE: Mid to late Norian (Litwin et al, 1991;Lucas, 1998a;Heckert et al, 2005;Parker, 2007;Irmis et al, 2007a Dromomeron romeri differs from Dromomeron gregorii and all other basal dinosauromorphs in possessing the following autapomorphies: (1) absence of a fourth trochanter; (2) presence of a sharp ridge on the anteromedial edge of the distal end of the femur; (3) presence of a lateral tuberosity on the anterolateral edge of the distal end of the femur; and (4) a large crest on the anteromedial edge of the astragalus and associated anteromedial concavity on the distal tibia.…”

Section: Protosuchus Richardsonimentioning

confidence: 99%

The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades

Nesbitt

2011

Bulletin of the American Museum of Natural History

742

2,561

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Section: Protosuchus Richardsonimentioning

confidence: 99%

The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades

Nesbitt

2011

Bulletin of the American Museum of Natural History

742

2,561

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“…The Chinle Formation of the Colorado Plateau in western North America is traditionally considered late CarnianNorian in age (e.g., Litwin et al, 1991;Lucas, 1998), but new U-Pb radioisotopic age constraints indicate that even the oldest fossiliferous strata are Norian in age (Riggs et al, 2003;Irmis and Mundil, 2008;Mundil et al, 2008). Footprint assemblages from the Newark Supergroup of eastern North America (e.g., Olsen et al, 2002) are tied to a high-resolution magnetostratigraphic record that is calibrated using palynomorph biostratigraphy (Kent and Olsen, 1999).…”

Section: Dating the Origin Of Dinosaursmentioning

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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“…Palynomorphs (Litwin et al 1991), invertebrates (Good 1998) and vertebrates (Long & Murry 1995;Lucas 1998) suggest a Norian age (equals Revueltian lvf of Lucas 1998) for these beds. Equivalent strata within a square kilometre of the quarry contain the remains of unionid bivalves, lungfish teeth and associated remains of the metoposaurid Apachesaurus, the diapsid Vancleavea (sensu Hunt et al 2002), a fragmentary phytosaur, the aetosaur Typothorax coccinarum, the 'rauisuchian' Postosuchus, a chatterjeeid, Chindesaurus, a coelophysoid theropod and additional material of Revueltosaurus.…”

Section: Geological Settingmentioning

confidence: 99%

The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs

Parker¹,

et al. 2005

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A new discovery of skeletons of Revueltosaurus callenderi from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona clearly shows that Revueltosaurus is not an ornithischian dinosaur as previously supposed. Features such as the presence of a postfrontal, crocodile-normal ankle and paramedian osteoderms with anterior bars place R. callenderi within the Pseudosuchia, closer to crocodylomorphs than to dinosaurs. Therefore, dental characters previously used to place Revueltosaurus within the Ornithischia evolved convergently among other archosaur taxa, and cannot be used to diagnose ornithischian dinosaur teeth. As a result, all other putative North American Late Triassic ornithischians, which are all based exclusively on teeth, are cast into doubt. The only reasonably well-confirmed Late Triassic ornithischians worldwide are Pisanosaurus mertii and an unnamed heterodontosaurid from Argentina. This considerably changes the understanding of early dinosaur diversity, distribution and evolution in the Late Triassic.

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Preliminary palynological zonation of the Chinle formation, southwestern U.S.A., and its correlation to the Newark supergroup (eastern U.S.A.)

Cited by 96 publications

References 19 publications

The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades

The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades

The origin and early radiation of dinosaurs

The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs

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