LAS ESPECIES DE ARCTODICTIS MERCERAT, 1891 (METATHERIA, BORHYAENIDAE), GRANDES MARSUPIALES CARNÍVOROS

FORASIEPI, A. M.; GOIN, F. J.; TAUBER, A. A.

Revista Española de Paleontología

Lugar: Madrid, España; Año: 2004 vol. 19 p. 1 - 22

0213-6937

During most of the Cenozoic, South American large carnivorous vertebrates were represented by phororhacid birds, crocodiles, giant snakes and, especially, metatherian mammals such as the Borhyaenidae. Between them, Arctodictis munizi Mercerat, 1891 represent the largest borhyaenid species known up to now. A new specimen of A. munizi collected in the Santa Cruz Formation (Middle Miocene) at Cañadón Las Totoras (Santa Cruz Province, Argentina), allowed us to describe its cranial anatomy, discuss the phylogenetic relationships of the genus Arctodictis, and to review the status of several problematic specimens. A study of the bearing sediments suggests environmental conditions characterized by a strong seasonality, open environments, frequent small streams, and grasslands. From the morphological and phylogenetic analysis we concluded that: (1) Arctodictis is a natural group supported by the following derived features: fused or strongly ankylosed dentaries at the symphysis; P/p 1 transversely oriented, m1-3 with a descendent labial lobe on the posterior half of the crown, opening of the infraorbitary foramen above M1, expanded palatines behind the last molar, and globe-shaped roots in the premolars. (2) The genus includes at least two species: A. munizi and A. sinclairi. Specimen UCMP 39250, referred by Marshall (1978) to cf. Arctodictis sp., would represent a big ‘prothylacinid-like’ sparassodont. (3) There is a wide variability in size and robustness among different individuals.