Nouveau silesaure
Discussion verrouillée
Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira
Sterling J. Nesbitt, Christian A. Sidor, Randall B. Irmis, Kenneth D. Angielczyk, Roger M. H. Smith & Linda A. Tsuji
Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA
Division of Paleontology, American Museum of Natural History, New York, New York 10024, USA
Burke Museum and Department of Biology, University of Washington, Seattle, Washington 98195, USA
Utah Museum of Natural History, 1390 E. Presidents Circle Salt Lake City, Utah 84112-0050, USA
Department of Geology & Geophysics, University of Utah, Salt Lake City, Utah 84112-0102, USA
Department of Geology, The Field Museum, 1400 South Lake Shore Drive, Chicago, Illinois 60605, USA
Karoo Palaeontology, Iziko: South African Museum, Cape Town 8000, South Africa
Museum für Naturkunde an der Humboldt-Universität zu Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany
Present address: Jackson School of Geosciences, The University of Texas at Austin, Texas 78712, USA.
An early herbivorous silesaur
The discovery of an almost complete skeleton of a new genus and species of silesaur, a close relative of the dinosaurs, ties up some of the loose ends in the fossil record of Middle Triassic reptiles. The new find is among the earliest known members of the Ornithodira, the avian line that also includes the dinosaurs and pterosaurs, dating to not long after the split between the two major archosaur groups — the ornithodirans, and crocodiles. Dentition and other features suggest silesaurs were not two-legged carnivores, as might have been expected, but larger and herbivorous. But the real interest is the early date, showing that we still know very little about the earliest stages of dinosaur and pterosaur evolution.
The early evolutionary history of Ornithodira (avian-line archosaurs) has hitherto been documented by incomplete (Lagerpeton ) or unusually specialized forms (pterosaurs and Silesaurus ). Recently, a variety of Silesaurus-like taxa have been reported from the Triassic period of both Gondwana and Laurasia, but their relationships to each other and to dinosaurs remain a subject of debate. Here we report on a new avian-line archosaur from the early Middle Triassic (Anisian) of Tanzania. Phylogenetic analysis places Asilisaurus kongwe gen. et sp. nov. as an avian-line archosaur and a member of the Silesauridae, which is here considered the sister taxon to Dinosauria. Silesaurids were diverse and had a wide distribution by the Late Triassic, with a novel ornithodiran bauplan including leaf-shaped teeth, a beak-like lower jaw, long, gracile limbs, and a quadrupedal stance. Our analysis suggests that the dentition and diet of silesaurids, ornithischians and sauropodomorphs evolved independently from a plesiomorphic carnivorous form. As the oldest avian-line archosaur, Asilisaurus demonstrates the antiquity of both Ornithodira and the dinosaurian lineage. The initial diversification of Archosauria, previously documented by crocodilian-line archosaurs in the Anisian, can now be shown to include a contemporaneous avian-line radiation. The unparalleled taxonomic diversity of the Manda archosaur assemblage indicates that archosaur diversification was well underway by the Middle Triassic or earlier.
Paru dans Nature.
article du Science Daily
PS: N'étant pas abonné à Nature, je n'ai pu vous fournir que le début de l'article, j'espère que vous trouverez mieux.
Posté par Spinosdu93
Posté par Captbot
J'ai l'article si quelqu'un le veut 
Posté par Spinosdu93
Si il est paru dans Nature, je le veux bien en entier ( et puis si quelqu'un a le pdf...) merci .
Posté par Lolo
Cet publi a été déjà annoncée ailleurs, dans le topic prévu à cet effet.
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