A new astrapothere (Mammalia, Meridiungulata) from La Meseta Formation, Seymour (Marambio) Island, and a reassessment of previous records of Antarctic astrapotheres

. BOND, M., KRAMARZ, A., MACPHEE, R.D.E. AND M. REGUERO MOLY, J.J.,SANTILLANA, S.N. Y S.A. MARENSSI.

AMERICAN MUSEUM NOVITATES

AMER MUSEUM NATURAL HISTORY

Lugar: New York; Año: 2011 p. 1 - 16

0003-0082

ABSTRACTDuring the past quarter century, the uplifted nearshore sediments comprising the EoceneLa Meseta Formation (LMF) of Seymour (Marambio) Island have produced a diverse assemblageof terrestrial mammals that closely, but not exactly, resembles late Early Eocene faunasfrom southern Patagonia. This assemblage includes the only astrapothere and litoptern fossilsknown from outside South America. The occurrence of astrapotheres in LMF was originallyindicated by fragmentary dental remains tentatively referred to family Trigonostylopidae on thebasis of their general resemblance to the Patagonian genus Trigonostylops Ameghino. In thiscontribution we describe a new astrapothere specimen from LMF; unlike specimens collectedpreviously, this one is a complete and excellently preserved lower cheek tooth, providing a basisfor a review of all previous records of Astrapotheria from this formation. This tooth (probablyp4 rather than m1) is sufficiently distinct from all other known astrapothere cheek teeth towarrant assignment to a new genus and species, Antarctodon sobrali. It has a transversallyelongated entoconid, resembling that observed in at least one specimen of the Mustersan genusAstraponotus, but the tooth as a whole is much lower crowned and less lophodont than in thelatter. Phylogenetic analysis suggests that Antarctodon is closer to genera classified by previousauthors as astrapotheriids (e.g., Albertogaudrya and Tetragonostylops) than it is to Trigonostylops.Reexamination of other LMF specimens previously referred to Trigonostylopidae revealsthat some specimens are attributable to this new taxon and others either are not astrapotheresat all or lack distinctive features. Consequently, at present the record of order Astrapotheria inAntarctica should be considered as restricted to non-trigonostylopids.