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Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira.
Nature. 2010 Mar 04; 464(7285):95-8.Nat

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.

Authors+Show Affiliations

Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

20203608

Citation

Nesbitt, Sterling J., et al. "Ecologically Distinct Dinosaurian Sister Group Shows Early Diversification of Ornithodira." Nature, vol. 464, no. 7285, 2010, pp. 95-8.
Nesbitt SJ, Sidor CA, Irmis RB, et al. Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature. 2010;464(7285):95-8.
Nesbitt, S. J., Sidor, C. A., Irmis, R. B., Angielczyk, K. D., Smith, R. M., & Tsuji, L. A. (2010). Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature, 464(7285), 95-8. https://doi.org/10.1038/nature08718
Nesbitt SJ, et al. Ecologically Distinct Dinosaurian Sister Group Shows Early Diversification of Ornithodira. Nature. 2010 Mar 4;464(7285):95-8. PubMed PMID: 20203608.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. AU - Nesbitt,Sterling J, AU - Sidor,Christian A, AU - Irmis,Randall B, AU - Angielczyk,Kenneth D, AU - Smith,Roger M H, AU - Tsuji,Linda A, PY - 2009/09/16/received PY - 2009/12/01/accepted PY - 2010/3/6/entrez PY - 2010/3/6/pubmed PY - 2010/4/20/medline SP - 95 EP - 8 JF - Nature JO - Nature VL - 464 IS - 7285 N2 - 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. SN - 1476-4687 UR - https://www.unboundmedicine.com/medline/citation/20203608/Ecologically_distinct_dinosaurian_sister_group_shows_early_diversification_of_Ornithodira_ L2 - https://doi.org/10.1038/nature08718 DB - PRIME DP - Unbound Medicine ER -