Middle Cenozoic penguin remains from the Patagonian Cordillera

ACOSTA HOSPITALECHE, C. ; GRIFFIN, M.

Bristol

Congreso; International Penguin Conference; 2013

Well preserved penguin bones (right humerus MLP 96-XII-2-1, a fragment of distal end of right coracoid MLP 96-XII-2-2, and a slightly damaged end of a left femur MLP 96-XII-3) were found in Middle Cenozoic marine beds. The Cerro Plataforma outcrop is unique because it is one of the few localities with Cenozoic marine fossils in the region; the outcrops of the fossil-bearing formation lie at about 1400 m a.s.l. and 500 km from the modern Atlantic coast and only 50 km from the Pacific Ocean (42° 20? S, 71° 51?W). This is the highest site in topographic terms in which penguin fossils occur and indicates a remarkable uplift for the area, probably from the middle Miocene on. There is still a debate about if the bearing beds are of Pacific or Atlantic origin. Associated fossil invertebrates mostly reveal Pacific affinity, and the shark tooth is cosmopolitan. An accurate identification of the fossil penguin was attained by means of a detailed description supplemented with quantitative analyses. Through direct comparisons with other remains and using morphogeometric tools, the specimens from Cerro Plataforma fall within the morphological range of Palaeospheniscus bergi. It has been mentioned as a frequent element in the Gaiman Formation (early Miocene, Argentina). This appears to point towards Atlantic affinities for the fossil penguin fauna in western Chubut. However, any certainty on the Atlantic or Pacific affinity of the bearing-rocks based on the penguin remains is challenged by the fact that there is material referable to this genus in rocks exposed along both sides of the present Andes. Palaeospheniscus has been cited with some doubts in the Bahía Inglesa Formation (middle Miocene-Pliocene, Chile); and certainly in the Chilcatay Formation (middle Miocene, Peru). However, the finding of Palaeospheniscus bergi in Cerro Plataforma would involve the development of a common marine assemblage in both coasts during the Neogene.