scholarly journals A re-evaluation of the enigmatic dinosauriform Caseosaurus crosbyensis from the Late Triassic of Texas, USA and its implications for early dinosaur evolution

2018 ◽  
Vol 63 ◽  
Author(s):  
Matthew Baron ◽  
Megan Williams
Keyword(s):  
Late Triassic ◽  
Dinosaur Evolution

Basal dinosauriform and theropod dinosaurs from the mid-late Norian (Late Triassic) of Poland: implications for Triassic dinosaur evolution and distribution

Palaeontology ◽  
2014 ◽  
Vol 57 (6) ◽  
pp. 1121-1142 ◽  
Author(s):  
Grzegorz Niedźwiedzki ◽  
Stephen L. Brusatte ◽  
Tomasz Sulej ◽  
Richard J. Butler
Keyword(s):  
Late Triassic ◽  
Theropod Dinosaurs ◽  
Dinosaur Evolution

scholarly journals A palaeoequatorial ornithischian and new constraints on early dinosaur diversification

2014 ◽  
Vol 281 (1791) ◽  
pp. 20141147 ◽  
Author(s):  
Paul M. Barrett ◽  
Richard J. Butler ◽  
Roland Mundil ◽  
Torsten M. Scheyer ◽  
Randall B. Irmis ◽  
...  
Keyword(s):  
South America ◽  
Growth Rates ◽  
Mass Extinction ◽  
Fossil Record ◽  
Early Jurassic ◽  
Late Triassic ◽  
Evolution Of Sociality ◽  
Northern South America ◽  
Dinosaur Evolution ◽  
Broad Scale

Current characterizations of early dinosaur evolution are incomplete: existing palaeobiological and phylogenetic scenarios are based on a fossil record dominated by saurischians and the implications of the early ornithischian record are often overlooked. Moreover, the timings of deep phylogenetic divergences within Dinosauria are poorly constrained owing to the absence of a rigorous chronostratigraphical framework for key Late Triassic–Early Jurassic localities. A new dinosaur from the earliest Jurassic of the Venezuelan Andes is the first basal ornithischian recovered from terrestrial deposits directly associated with a precise radioisotopic date and the first-named dinosaur from northern South America. It expands the early palaeogeographical range of Ornithischia to palaeoequatorial regions, an area sometimes thought to be devoid of early dinosaur taxa, and offers insights into early dinosaur growth rates, the evolution of sociality and the rapid tempo of the global dinosaur radiation following the end-Triassic mass extinction, helping to underscore the importance of the ornithischian record in broad-scale discussions of early dinosaur history.

scholarly journals The first 50 Myr of dinosaur evolution: macroevolutionary pattern and morphological disparity

2008 ◽  
Vol 4 (6) ◽  
pp. 733-736 ◽  
Author(s):  
Stephen L Brusatte ◽  
Michael J Benton ◽  
Marcello Ruta ◽  
Graeme T Lloyd
Keyword(s):  
Taxonomic Diversity ◽  
Early Jurassic ◽  
Late Triassic ◽  
Steady Increase ◽  
Morphological Disparity ◽  
Ecological Release ◽  
Driving Mechanisms ◽  
Faunal Abundance ◽  
Evolutionary Radiation ◽  
Dinosaur Evolution

The evolutionary radiation of dinosaurs in the Late Triassic and Early Jurassic was a pivotal event in the Earth's history but is poorly understood, as previous studies have focused on vague driving mechanisms and have not untangled different macroevolutionary components (origination, diversity, abundance and disparity). We calculate the morphological disparity (morphospace occupation) of dinosaurs throughout the Late Triassic and Early Jurassic and present new measures of taxonomic diversity. Crurotarsan archosaurs, the primary dinosaur ‘competitors’, were significantly more disparate than dinosaurs throughout the Triassic, but underwent a devastating extinction at the Triassic–Jurassic boundary. However, dinosaur disparity showed only a slight non-significant increase after this event, arguing against the hypothesis of ecological release-driven morphospace expansion in the Early Jurassic. Instead, the main jump in dinosaur disparity occurred between the Carnian and Norian stages of the Triassic. Conversely, dinosaur diversity shows a steady increase over this time, and measures of diversification and faunal abundance indicate that the Early Jurassic was a key episode in dinosaur evolution. Thus, different aspects of the dinosaur radiation (diversity, disparity and abundance) were decoupled, and the overall macroevolutionary pattern of the first 50 Myr of dinosaur evolution is more complex than often considered.

The roles of herbivory and omnivory in early dinosaur evolution

2010 ◽  
Vol 101 (3-4) ◽  
pp. 383-396 ◽  
Author(s):  
Paul M. Barrett ◽  
Richard J. Butler ◽  
Sterling J. Nesbitt
Keyword(s):  
Relative Abundance ◽  
Competitive Interactions ◽  
Late Triassic ◽  
Current Evidence ◽  
Faunal Turnover ◽  
Rapid Diversification ◽  
Ecological Dominance ◽  
Dinosaur Evolution ◽  
Carnian Stage ◽  
Trophic Specialisation

ABSTRACTHerbivorous and omnivorous dinosaurs were rare during the Carnian stage of the Late Triassic. By contrast, the succeeding Norian stage witnessed the rapid diversification of sauropodomorphs and the rise of the clade to ecological dominance. Ornithischians, by contrast, remained relatively rare components of dinosaur assemblages until much later in the Mesozoic. The causes underlying the differential success of ornithischians and sauropodomorphs remain unclear, but might be related to trophic specialisation. Sauropodomorphs replaced an established herbivore guild consisting of rhynchosaurs, aetosaurs and basal synapsids, but this faunal turnover appears to have been opportunistic and cannot be easily attributed to either competitive interactions or responses to floral change. Consideration of diversity patterns and relative abundance suggests that the ability to eat plants might have been a major factor promoting sauropodomorph success, but that it was less important in the early evolution of Ornithischia. On the basis of current evidence it is difficult to determine the diet of the ancestral dinosaur and scenarios in which omnivory or carnivory represent the basal condition appear equally likely.

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