![]() ![]() A better understanding of the Permian saurian record is fundamental for providing more accurate fossil constraints on the calibration of the crocodile-lizard ( = bird-lizard) divergence, a major split within vertebrates that is of keen interest to molecular and evolutionary biologists and vertebrate paleontologists alike –. Parrington's “problematic reptile” from Tanzania, UMZC T836 ). Multiple less completely known specimens have been also argued to be Permian members of Sauria (e.g. ![]() The best source of information on the early history of Sauria comes from the numerous fossils of the well-known basal archosauromorph Protorosaurus speneri from the Late Permian of Germany and England –. pre-Mesozoic) evolutionary history of Sauria is poorly known and there has been substantial debate regarding the late Paleozoic (i.e. These lineages formed important components of Triassic continental assemblages, and include kuehneosaurids, rhynchosaurs, proterosuchids, erythrosuchids, euparkeriids, doswelliids and proterochampsids –. The stem-groups of Lepidosauria (non-lepidosaurian Lepidosauromorpha) and Archosauria (non-archosaurian Archosauromorpha) also include several morphologically disparate saurian lineages that were mostly restricted in time to the Triassic. Saurians, or crown group diapsids, are highly taxonomically and morphologically diverse in extant ecosystems, with around 9,400 lepidosaur (snakes, lizards and rhynchocephalians) and 10,000 archosaur (birds and crocodilians) species, including cursorial, semi-aquatic, marine, fossorial and volant forms. Early archosauromorph growth strategies appear to be more diverse than previously suggested based on new data on the osteohistology of Aenigmastropheus. The occurrences of basal archosauromorphs in the northern (30°N) and southern (55°S) parts of Pangea imply a wider paleobiogeographic distribution for the group during the Late Permian than previously appreciated. Our revision suggests a minimum fossil calibration date for the crocodile-lizard split of 254.7 Ma. The assignment of Archosaurus rossicus from the latest Permian of Russia to the archosauromorph clade Proterosuchidae is supported. 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. 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 most informative Permian archosauromorph is Protorosaurus speneri from the middle Late Permian of Western Europe. 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. 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. Several Permian specimens have been referred to Sauria, but the phylogenetic affinity of some of these records remains questionable. Saurians have a very rich Mesozoic and Cenozoic fossil record, but their late Paleozoic (Permian) record is problematic. 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. 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. ![]()
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