INVESTIGADORES
EZCURRA Martin Daniel
congresos y reuniones científicas
Título:
THE PERMIAN ARCHOSAUROMORPH RECORD REVISITED: A NEW SPECIES FROM TANZANIA AND THE POTENTIALLY OLDEST ARCHOSAURIFORM
Autor/es:
EZCURRA, M. D.; BUTLER, R. J.; SCHEYER, T. M.
Lugar:
Los Angeles
Reunión:
Congreso; 73th Annual Meeting of the Society of Vertebrate Paleontology; 2013
Resumen:
Archosauromorphs include all diapsids closer to crocodiles and birds than tolepidosaurs. The group has a very rich Mesozoic and Cenozoic fossil record, but thePaleozoic record is restricted to a handful of Late Permian specimens. The mostinformative Permian archosauromorph so far discovered is Protorosaurus speneri fromthe middle Late Permian of Western Europe. In addition, there are several less wellknownputative archosauromorphs from Russia and Africa. We review these records hereand include several of them in a quantitative phylogenetic analysis for the first time. Thisphylogenetic analysis included a broad taxonomic sampling of basal synapsids, basaldiapsids and saurians. We could not find archosauromorph apomorphies in a supposedLate Permian proterosuchid cervical vertebra from South Africa (Bernard Price Institutefor Palaeontological Research specimen BP/1/4220), and consider this specimen tobelong to an indeterminate amniote. BP/1/4220 possesses striking features that are notpresent in other amniotes of which we are aware, such as posteriorly extended, wide andalmost horizontally oriented accessory processes between the postzygapophyses. Aproblematic reptile (University Museum of Zoology, Cambridge specimen UMZC T836)from the Late Permian of Tanzania, first described in the 1950s, was recovered in thephylogenetic analysis as a protorosaur at the base of Archosauromorpha and is probablydiagnosable as a new species. The position of UMZC T836 within Archosauromorpha issupported by the presence of three well-developed laminae in the cervico-dorsal neuralarches and the absence of a humeral entepicondylar foramen. The supposed protorosaurEorasaurus olsoni from the middle Late Permian of Russia was recovered withinArchosauriformes, being more closely related to crown archosaurs than to proterosuchids,implying that this species may be the oldest known archosauriform. However, thefragmentary nature of the known material of this taxon and the low character support forthis position means that this identification is currently tentative. Archosaurus rossicusfrom the latest Permian of Russia was found to be more closely related to Proterosuchusfergusi than to other archosauromorphs and represents a valid species. The revisionconducted here suggests a minimum fossil calibration date for the crocodile-lizard split of254.7 Ma. The occurrences of Protorosaurus speneri close to the paleo-Equator andUMZC T836 in high paleolatitudes of southern Pangea imply a wider paleobiogeographicdistribution for archosauromorphs during the Late Permian than previously appreciated.