INVESTIGADORES
EZCURRA Martin Daniel
artículos
Título:
The Origin and Early Evolution of Sauria: Reassessing the Permian Saurian Fossil Record and the Timing of the Crocodile-Lizard Divergence
Autor/es:
EZCURRA, M. D.; SCHEYER, T. M.; BUTLER, R. J.
Revista:
PLOS ONE
Editorial:
PUBLIC LIBRARY SCIENCE
Referencias:
Lugar: San Francisco; Año: 2014 vol. 9
ISSN:
1932-6203
Resumen:
Sauria is the crown-group of Diapsida and is subdivided into Lepidosauromorpha and Archosauromorpha, comprising a
high percentage of the diversity of living and fossil tetrapods. The split between lepidosauromorphs and archosauromorphs
(the crocodile-lizard, or bird-lizard, divergence) is considered one of the key calibration points for molecular analyses of
tetrapod phylogeny. Saurians have a very rich Mesozoic and Cenozoic fossil record, but their late Paleozoic (Permian) record
is problematic. Several Permian specimens have been referred to Sauria, but the phylogenetic affinity of some of these
records remains questionable. We reexamine and review all of these specimens here, providing new data on early saurian
evolution including osteohistology, and present a new morphological phylogenetic dataset. We support previous studies
that find that no valid Permian record for Lepidosauromorpha, and we also reject some of the previous referrals of Permian
specimens to Archosauromorpha. The most informative Permian archosauromorph is Protorosaurus speneri from the middle
Late Permian of Western Europe. A historically problematic specimen from the Late Permian of Tanzania is redescribed and
reidentified as a new genus and species of basal archosauromorph: Aenigmastropheus parringtoni. The supposed
protorosaur Eorasaurus olsoni from the Late Permian of Russia is recovered among Archosauriformes and may be the oldest
known member of the group but the phylogenetic support for this position is low. The assignment of Archosaurus rossicus
from the latest Permian of Russia to the archosauromorph clade Proterosuchidae is supported. Our revision suggests a
minimum fossil calibration date for the crocodile-lizard split of 254.7 Ma. The occurrences of basal archosauromorphs in the
northern (30uN) and southern (55uS) parts of Pangea imply a wider paleobiogeographic distribution for the group during
the Late Permian than previously appreciated. Early archosauromorph growth strategies appear to be more diverse than
previously suggested based on new data on the osteohistology of Aenigmastropheus.