NEW VERTEBRATES FROM THE PERMIAN PEDRA DE FOGO FORMATION, PARNAÍBA BASIN, NORTHEASTERN BRAZIL

ANGIELCZYK, KEN; CISNEROS, JUAN; MARSICANO, CLAUDIA; RICHTER, MARTHA

Congreso; Biennial Conference PSSA; 2012

Permian fossils, including petrified wood, fish, and a temnospondyl amphibian, were first discovered in the Pedra de Fogo Formation (PFF) of the Parnaíba Basin in the first half of the 20th century. Their precise age is uncertain, with estimates spanning most of the Permian. In 2011-2013 our team conducted fieldwork in the PFF to determine its age, depositional environments, and vertebrate fauna. The PFF accumulated in a large shallow intra-continental sag basin. With progressive climatic drying. paleoenvironments changed from a large shallow epeiric sea to an expansive alluvial plain culminating in isolated playas between extensive aeolian dune fields. Fish are the most abundant vertebrate fossils in the PFF. Ctenacanths, xenacanths, and other chondrichthyans, including new taxa, dominate the fauna of wavy-bedded sandstones and siltstones that accumulated within the basin depocenter. Petalodont holocephalans and the endemic Anisopleurodontis are common in the nearshore and evaporitic shoreline facies. We also collected specimens of the shark Glikmanius, which occurs in the Lower Permian of the USA and the Carboniferous of Russia and Europe. We recognize at least four distinct tooth plate morphologies. In more continental deposits in the upper PFF, we collected lower actinopterygians and coelacanthiforms with close affinities to Mesozoic taxa. The archegosaurid Prionosuchus is the only tetrapod previously known from the PFF. We collected additional temnospondyl amphibians from two areas in the basin, representing at least three new taxa. Specimens from the eastern edge of the basin resemble tupilakosaurids and rhinesuchids, whereas those from the central basin may represent rhitidosteids and a fragment attributable to Prionosuchus. At least one specimen may preserve soft tissue impressions. In the Permian, the Parnaíba Basin was located in equatorial Pangaea, at a similar latitude as the Moradi Formation of Niger. Like the Moradi, the PFF includes an anachronistic mixture of taxa, suggesting that such faunas may have been common in central Pangaea. Yet, the PFF appears to include a mix of clades best known from the Early Permian and Mesozoic, whereas the Moradi includes a mix of Early and Late Permian taxa. Further research will be necessary to better establish the number of distinct time horizons in the PFF, and their correlations within the basin and with other basins. The PFF shows great potential to provide new insight into Permian biogeography and potentially the end-Permian mass extinction.