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New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation.
BMC Evol Biol. 2014 Jun 10; 14:128.BE

Abstract

BACKGROUND

The origin and early radiation of archosaurs and closely related taxa (Archosauriformes) during the Triassic was a critical event in the evolutionary history of tetrapods. This radiation led to the dinosaur-dominated ecosystems of the Jurassic and Cretaceous, and the high present-day archosaur diversity that includes around 10,000 bird and crocodylian species. The timing and dynamics of this evolutionary radiation are currently obscured by the poorly constrained phylogenetic positions of several key early archosauriform taxa, including several species from the Middle Triassic of Argentina (Gracilisuchus stipanicicorum) and China (Turfanosuchus dabanensis, Yonghesuchus sangbiensis). These species act as unstable 'wildcards' in morphological phylogenetic analyses, reducing phylogenetic resolution.

RESULTS

We present new anatomical data for the type specimens of G. stipanicicorum, T. dabanensis, and Y. sangbiensis, and carry out a new morphological phylogenetic analysis of early archosaur relationships. Our results indicate that these three previously enigmatic taxa form a well-supported clade of Middle Triassic archosaurs that we refer to as Gracilisuchidae. Gracilisuchidae is placed basally within Suchia, among the pseudosuchian (crocodile-line) archosaurs. The approximately contemporaneous and morphologically similar G. stipanicicorum and Y. sangbiensis may be sister taxa within Gracilisuchidae.

CONCLUSIONS

Our results provide increased resolution of the previously poorly constrained relationships of early archosaurs, with increased levels of phylogenetic support for several key early pseudosuchian clades. Moreover, they falsify previous hypotheses suggesting that T. dabanensis and Y. sangbiensis are not members of the archosaur crown group. The recognition of Gracilisuchidae provides further support for a rapid phylogenetic diversification of crown archosaurs by the Middle Triassic. The disjunct distribution of the gracilisuchid clade in China and Argentina demonstrates that early archosaurs were distributed over much or all of Pangaea although they may have initially been relatively rare members of faunal assemblages.

Authors+Show Affiliations

School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. r.butler.1@bham.ac.uk.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

Language

eng

PubMed ID

24916124

Citation

Butler, Richard J., et al. "New Clade of Enigmatic Early Archosaurs Yields Insights Into Early Pseudosuchian Phylogeny and the Biogeography of the Archosaur Radiation." BMC Evolutionary Biology, vol. 14, 2014, p. 128.
Butler RJ, Sullivan C, Ezcurra MD, et al. New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation. BMC Evol Biol. 2014;14:128.
Butler, R. J., Sullivan, C., Ezcurra, M. D., Liu, J., Lecuona, A., & Sookias, R. B. (2014). New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation. BMC Evolutionary Biology, 14, 128. https://doi.org/10.1186/1471-2148-14-128
Butler RJ, et al. New Clade of Enigmatic Early Archosaurs Yields Insights Into Early Pseudosuchian Phylogeny and the Biogeography of the Archosaur Radiation. BMC Evol Biol. 2014 Jun 10;14:128. PubMed PMID: 24916124.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation. AU - Butler,Richard J, AU - Sullivan,Corwin, AU - Ezcurra,Martín D, AU - Liu,Jun, AU - Lecuona,Agustina, AU - Sookias,Roland B, Y1 - 2014/06/10/ PY - 2014/02/06/received PY - 2014/06/04/accepted PY - 2014/6/12/entrez PY - 2014/6/12/pubmed PY - 2014/7/31/medline SP - 128 EP - 128 JF - BMC evolutionary biology JO - BMC Evol Biol VL - 14 N2 - BACKGROUND: The origin and early radiation of archosaurs and closely related taxa (Archosauriformes) during the Triassic was a critical event in the evolutionary history of tetrapods. This radiation led to the dinosaur-dominated ecosystems of the Jurassic and Cretaceous, and the high present-day archosaur diversity that includes around 10,000 bird and crocodylian species. The timing and dynamics of this evolutionary radiation are currently obscured by the poorly constrained phylogenetic positions of several key early archosauriform taxa, including several species from the Middle Triassic of Argentina (Gracilisuchus stipanicicorum) and China (Turfanosuchus dabanensis, Yonghesuchus sangbiensis). These species act as unstable 'wildcards' in morphological phylogenetic analyses, reducing phylogenetic resolution. RESULTS: We present new anatomical data for the type specimens of G. stipanicicorum, T. dabanensis, and Y. sangbiensis, and carry out a new morphological phylogenetic analysis of early archosaur relationships. Our results indicate that these three previously enigmatic taxa form a well-supported clade of Middle Triassic archosaurs that we refer to as Gracilisuchidae. Gracilisuchidae is placed basally within Suchia, among the pseudosuchian (crocodile-line) archosaurs. The approximately contemporaneous and morphologically similar G. stipanicicorum and Y. sangbiensis may be sister taxa within Gracilisuchidae. CONCLUSIONS: Our results provide increased resolution of the previously poorly constrained relationships of early archosaurs, with increased levels of phylogenetic support for several key early pseudosuchian clades. Moreover, they falsify previous hypotheses suggesting that T. dabanensis and Y. sangbiensis are not members of the archosaur crown group. The recognition of Gracilisuchidae provides further support for a rapid phylogenetic diversification of crown archosaurs by the Middle Triassic. The disjunct distribution of the gracilisuchid clade in China and Argentina demonstrates that early archosaurs were distributed over much or all of Pangaea although they may have initially been relatively rare members of faunal assemblages. SN - 1471-2148 UR - https://www.unboundmedicine.com/medline/citation/24916124/New_clade_of_enigmatic_early_archosaurs_yields_insights_into_early_pseudosuchian_phylogeny_and_the_biogeography_of_the_archosaur_radiation_ L2 - https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-14-128 DB - PRIME DP - Unbound Medicine ER -