Upper Cretaceous Antarctic Plesiosaurs: The heart area of the Weddellian Biogeographic Province

O'GORMAN, J.; FERNÁNDEZ, MARTA; REGUERO, MARCELO

Simposio; XII International Symposium on Antarctic Earth Science (ISAES 2015); 2015

The Upper Cretaceous plesiosaur record from the Weddellian Province (i.e. Patagonia, WesternAntarctica and New Zealand, WP hereafter) extends from the uppermost Coniacian to the uppermostMaastrichtian. The sequence records ~36 ma of evolution of aplesiosaur fauna at high latitud across threecontinents. During this time the WP was afected by a cooling trend of the Weddellian Province which startin the Coniacian until the end of the Cretaceous. The last 40 years of Antarctic expeditions of the IAAUNLPhave produced the largest collection of Antarctic plesiosaurs and allows the understanding of themain features of this plesiosaur fauna, its main temporal changes and possible correlation with biotic andabiotic factors. The main features of the plesiosaur fauna from the WP are 1) the presence of thearistonectine elasmosaurids since the upper Campanian and 2) the absence of post-Santonian Antarcticpolycotylids, the scarcity of New Zealand polycotylids records and the restriction to non-marine normalenvironments inSouth America. The explanation of these requires an understanding of the stratigraphicaldistribution, phylogeny and paleobiology of the three main involved groups: elasmosaurids (aristonectineand non-aristonectine) and polycotylids. This is the general objective and main scope of our current work.Here a general background and preliminary results are commented. The Antarctic plesiosaurs have beencollected from three formations: the (upper Coniacian?, Santonian-lower Campanian Santa Marta Fm.,the upper Campanian-lower Maastrichtian Snow Hill Island Fm. and the Maastrichtian-lower PaleoceneLópez de Bertodano Fm. This stratigraphic interval comprises environments from nearshore, transgresiveand regresive shelfs, deltaic distal wedge and stuary.