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Prince Rupert, Canada

Botha-Brink J.,Karoo Palaeontology | Botha-Brink J.,University of the Free State | Angielczyk K.D.,The Field Museum
Zoological Journal of the Linnean Society | Year: 2010

Dicynodonts were the most diverse and abundant herbivorous therapsids of the Permo-Triassic. They include Lystrosaurus, one of the few taxa known to survive the end-Permian extinction and the most abundant tetrapod during the Early Triassic postextinction recovery. Explanations for the success of Lystrosaurus and other dicynodonts remain controversial. This study presents an assessment of dicynodont growth patterns using bone histology, with special focus on taxa associated with the end-Permian extinction event. Bone histological analysis reveals a high cortical thickness throughout the clade, perhaps reflecting a phylogenetic constraint. Growth rings are absent early in ontogeny, and combined with high vascular density, indicate rapid, sustained growth up to the subadult stage. Extraordinarily enlarged vascular channels are present in the midcortex of many dicynodonts, including adults, and may have facilitated a more efficient assimilation of nutrients and rapid bone growth compared to other therapsids. Both increased channel density and enlarged vascular channels evolved at or near the base of major radiations of dicynodonts, implying that the changes in growth and life history they represent may have been key to the success of dicynodonts. Furthermore, this exceptionally rapid growth to adulthood may have contributed to the survival of Lystrosaurus during the end-Permian extinction and its dominance during the postextinction recovery period. © 2010 The Linnean Society of London. Source

Peecook B.R.,University of Washington | Sidor C.A.,University of Washington | Nesbitt S.J.,University of Washington | Smith R.M.H.,Karoo Palaeontology | And 2 more authors.
Journal of Vertebrate Paleontology | Year: 2013

Recent discoveries have shown that non-dinosaurian dinosauromorphs were morphologically diverse, globally distributed, and have a stratigraphic range extending into the Upper Triassic. Silesauridae, the sister group to Dinosauria, contains at least seven species. Here we describe Lutungutali sitwensis, gen. et sp. nov., the first silesaurid from the upper portion of the Ntawere Formation of the Luangwa Basin, Zambia. The upper Ntawere Formation has been correlated with subzone C of the Cynognathus Assemblage Zone of the Karoo Basin in South Africa and the Lifua Member of the Manda beds in the Ruhuhu Basin in Tanzania, both of which are considered Anisian in age and the latter has yielded the silesaurid Asilisaurus kongwe. The results of our phylogenetic analysis, including a new pelvic character, allies Lutungutali with Upper Triassic silesaurids such as Silesaurus, Sacisaurus, and Eucoelophysis rather than with the possibly coeval Asilisaurus. The Zambian silesaurid shares a laterally oriented brevis fossa on the ilium and a transversely thin ischium in cross-section with Upper Triassic forms. Silesaurids were more diverse during their early evolution in the Anisian than previously suspected. Lutungutali and Asilisaurus are the two oldest known members of the bird-line archosaurs represented by body fossils. Together they show that a subclade of bird-line archosaurs was diversifying soon after its origin, building further support for the rapid diversification of Archosauria in the wake of the Permo-Triassic extinction. SUPPLEMENTAL DATA - Supplemental materials are available for this article for free at www.tandfonline.com/UJVP © 2013 by the Society of Vertebrate Paleontology. Source

Ruta M.,University of Lincoln | Botha-Brink J.,Karoo Palaeontology | Mitchell S.A.,University of the Free State | Benton M.J.,University of Bristol
Proceedings of the Royal Society B: Biological Sciences | Year: 2013

Cynodont therapsids diversified extensively after the Permo-Triassic mass extinction event, and gave rise to mammals in the Jurassic.We use an enlarged and revised dataset of discrete skeletal characters to build a newphylogeny for all main cynodont clades from the Late Permian to the Early Jurassic, and we analyse models of morphological diversification in the group. Basal taxa and epicynodonts are paraphyletic relative to eucynodonts, and the latter are divided into cynognathians and probainognathians, with tritylodonts and mammals forming sister groups. Disparity analyses reveal a heterogeneous distribution of cynodonts in a morphospace derived from cladistic characters. Pairwise morphological distances are weakly correlated with phylogenetic distances. Comparisons of disparity by groups and through time are nonsignificant, especially after the data are rarefied. A disparity peak occurs in the Early/Middle Triassic, after which period the mean disparity fluctuates little. Cynognathians were characterized by high evolutionary rates and high diversity early in their history, whereas probainognathian rates were low. Community structure may have been instrumental in imposing different rates on the two clades. © 2013 The Authors. Source

Modesto S.P.,Cape Breton University | Botha-Brink J.,Karoo Palaeontology | Botha-Brink J.,University of the Free State
Journal of African Earth Sciences | Year: 2010

The best record of continental tetrapod faunas crossing the Permo-Triassic boundary (PTB) is found in the Karoo Basin of South Africa. Similar records are not known elsewhere among the former Gondwanan land masses, but it was recently proposed on the basis of palaeontological evidence that the Buena Vista Formation of Uruguay preserves a South American record of continental PTB tetrapods. The Buena Vista Formation was previously correlated to the Lower Triassic (Olenekian) Sanga do Cabral Formation of Brazil on the basis of lithostratigraphic evidence, but recent collecting in the former unit has produced a tetrapod fauna that is distinct to that documented for the latter. The unequivocal tetrapod fossils that have been described thus far from the Buena Vista Formation include indeterminate mastodonsaurid temnospondyls, a plagiosauroid temnospondyl, and a procolophonid reptile. The temnospondyls belong to Triassic groups, whereas the procolophonid is allied most closely with Early Triassic taxa from the Karoo Basin. We conclude that there is no compelling palaeontological evidence for placing any part of the Buena Vista Formation in the Permian. A precise placement of the Buena Vista Formation in the Triassic on the basis of its tetrapod fauna is not possible at this time. Accordingly, the Karoo Basin of South Africa remains the only Gondwanan basin that records a PTB tetrapod fauna. © 2009 Elsevier Ltd. Source

Modesto S.P.,Cape Breton University | Scott D.M.,University of Toronto | Botha-Brink J.,Karoo Palaeontology | Reisz R.R.,University of Toronto | Reisz R.R.,University of the Free State
Journal of Vertebrate Paleontology | Year: 2010

A small skull collected from the base of the Katberg Formation of South Africa represents a new Early Triassic procolophonid parareptile. Phonodus dutoitorum, gen. et sp. nov., is diagnosed by a roughly straight ventral temporal margin, prefrontals that contact each other along the dorsal midline, presence of a large posterior maxillary tooth, an edentulous pterygoid, a reduced transverse flange of the pterygoid, and other autapomorphies. A cladistic analysis identifies P. dutoitorum as a basal member of the procolophonid clade Leptopleuroninae. The presence of large maxillary teeth, their positioning ventral to strongly developed antorbital buttresses, and the loss of the ventral temporal emargination are suggestive of a durophagous diet. Phonodus dutoitorum is recognized as the oldest known leptopleuronine. Optimization of geographic distributions onto procolophonid phylogeny indicates that the presence of P. dutoitorum in the Karoo Basin of South Africa is explained most parsimoniously as the result of migration from Laurasia. Phonodus dutoitorum is the fifth procolophonoid species to be described from the Induan of the Karoo Basin, providing further support for the hypothesis that procolophonoid evolution was not greatly perturbed by the end-Permian extinction event. © 2010 by the Society of Vertebrate Paleontology. Source

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