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- Title
Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira.
- Authors
Nesbitt, Sterling J.; Sidor, Christian A.; Irmis, Randall B.; Angielczyk, Kenneth D.; Smith, Roger M. H.; Tsuji, Linda A.
- Abstract
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.
- Subjects
ORNITHODOROS; ARGASIDAE; PTEROSAURIA; TRIASSIC stratigraphic geology; DINOSAURS; PHYLOGENY; QUADRUPEDALISM; SAUROPODOMORPHA; TAXONOMY
- Publication
Nature, 2010, Vol 464, Issue 7285, p95
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature08718