Teeth, legs, and ears: new evidence to fill the Paleogene record of land mammals from West Antarctica

GELFO J. N.; REGUERO, M.A.,

Hobart OSC

Congreso; SCAR Open Science Conferences; 2020

Scientific Committee on Antarctic Research

The current absence of terrestrial mammals in Antarctica contrast with the information from their fossil record, which indicate that this continent, played an outstanding role in mammalian evolution. Paleobiogeographical proxies suggest that West Antarctica probably functioned as an origin center for Australosphenida during the Jurassic. Also as a dispersal corridor during the Late Cretaceous?/earliest Paleogene, from Australia to South America for monotremes, and from South America to Australia for marsupials. In contrast, Antarctica was a sieve for placentals. We report here new land-mammal specimens from different levels and localities of the Eocene La Meseta and Submeseta formations in Marambio/Seymour Island: 1) A medial portion of a petrosal bone from Acantilados II Allomember at the locality IAA 1/13. 2) A mesiodistal half of a lower first premolar from the lower coquina bed of Cucullaea I Allomember at the site IAA 2/16. 3) Two teeth from the naticid bed of the Cucullaea I Allomember at the classic locality IAA 1/90. One is a fragmentary tooth with an enamel thinner than in sparnotheriodontids and astrapotherians from the same stratigraphic level. The other is a complete incisiviform of an herbivorous mammal of half the size to the incisive of Notiolofos arquinotiensis. 4) Several fragments of an upper tooth, also from the naticid beds were found in IAA 1/95. 5) A tibia from Submeseta II Allomember represents the first terrestrial mammal record in the locality DPV 13/84. These findings suggest that Eocene diversity in Antarctica was higher than previous interpretations from the fossil record.