Preliminary analysis of a new Didolodontidae `Condylarthra´ (Mammalia) from the Paleogene of Itaboraí Basin, Brazil.

GELFO J. N.; BERGQVIST, P. L.

Cleveland, Ohio, USA.

Otro; 68th Annual Meeting of the Society of Vertebrate Paleontology, Cleveland, Ohio, USA.; 2008

Society of Vertebrate Paleontology

An extraordinary diversity of mammals has been recovered from fissure fill deposits with marls and collapse breccias from São José de Itaboraí Basin, at Rio de JaneiroState. This fauna was the basis for the Itaboraian SALMA (South American Land Mammal Age), also recognized at Las Flores locality, in Patagonia, Argentina; and considered in different works as late Paleocene or early Eocene. The Itaboaraian fauna shows a great diversity of mammals representedby metatherian (e.g. Sparassodonta, Didelphimorphia and Microbiotheria) and eutherian (e.g. Notoungulata, Astrapotheria, Xenungulata and Xenarthra). Two lineages of South American strict bunodont ungulates, the Didolodontidae condylarths and the Protolipternidae litopterns, are best represented in the Itaboraian than in any other SALMA. Undescribed remains belong to a left M3 (FZB 1413PV) and a left m2? (MNRJ 4465V) suggests the presence of at least another didolodontid taxon. Compared to other Itaboraian taxa both teeth are larger than Paulacoutoia protocenica but smaller than Lamegoia conodonta. As in them, transverse HSB are present in the enamel. The main distinct features of the M3 are: an almost squared outline due to the shortness of the labiolingual axis; labial cingulum absent; mesial and distal cingula large and crenulated; weak and twined hypocone at the end of the distal cingulum and separated from the protocone, but not as much as in Didolodus multicuspis; preparaconular and postmetaconular cristae directed to the mid portion of paracone and metacone respectively; straight centrocristawith a small cuspule between paracone and metacone. The m2? shows a trigonid somewhat wider than talonid, and with a wide trigonid basin; paraconid mesial and connated to metaconid; metacristid unusually high and strong; talonid basin opens lingually through a furrow due to the development of the hypoconid and entoconid; hypoconid subequal to protoconid; cristid obliqua running to the labial side of the metaconid and without mesostyle; hypoconulid distally placed and without postcristid and hypocristid. These remains increase the diversity of strict bunodontungulates for the Itaboraian SALMA.