New Fossil Discoveries from the Miocene Santa Cruz Formation of Argentina

Abstract

The Miocene Santa Cruz Formation of Patagonian Argentina yields well preserved skeletons of many groups of mammals, notably platyrrhine primates and sloths – groups known today from only tropical/subtropical environments and occupying purely arboreal niches. The classic high latitude (51 degrees South) Patagonian localities of this formation have been worked by many paleontologists for more than a century. Our project shifts the emphasis from the classical localities of the Lower Member (ELCm) to the comparatively less studied Upper Member (ELAm) farther south. The ELAm was originally reconstructed as a cooler, drier, and more open‐woodland environment. This paleoecological reconstruction is at odds with recent radiometric dates placing the Mid Miocene Climatic Optimum within the ELAm; the new dates imply that the ELAm was generally warmer and wetter than the ELCm. Our recent field expedition focused on three known localities of the ELAm. One of these (Monte Tigre) yielded abundant mammalian remains, including a diverse assemblage of sloths some of which appear to have been semi‐arboreal. There we also collected the first plant macrofossils known from the ELAm (mostly Nothofagus leaf impressions). Another locality (Cañadon Palos) yielded abundant small mammal remains, including the rare marsupial Abderites. The third locality (Cabo Buen Tiempo) yielded sporadic small mammal fossils (mainly rodents and small armadillos) from a tuffaceous sediment. Future work at these localities will include 1. stratigraphic correlation across 25 kilometers of beach cliffs and shelf, 2. continued fossil collecting at the known ELAm localities, 3. prospecting for new ELAm localities, and 4. paleobiological comparisons between ELAm and ELCm mammals focusing on primates and sloths. New fossils from other vertebrate groups and plant remains will permit a richer paleoecological reconstruction of the ELAm than was previously possible.Support or Funding InformationGenerous support for this study was provided by an American Association of Anatomists Fellows Grant to J. Perry.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.