INVESTIGADORES
LECUONA Agustina
artículos
Título:
New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation.
Autor/es:
BUTLER, R.J.; SULLIVAN, C.; EZCURRA, M.D.; LIU, J.; LECUONA, A.; SOOKIAS, R.B.
Revista:
BMC EVOLUTIONARY BIOLOGY
Editorial:
BIOMED CENTRAL LTD
Referencias:
Lugar: Londres; Año: 2014 vol. 14 p. 1 - 16
ISSN:
1471-2148
Resumen:
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.