Las especies de Arctodictis Mercerat, 1891 (Metatheria, Borhyaenidae), grandes carnívoros del Mioceno de América del Sur

FORASIEPI, A., F. J. GOIN Y A. A. TAUBER.

REVISTA ESPAÑOLA DE PALEONTOLOGIA

Sociedad Española de Paleontología

Lugar: Madrid; 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. One of the largest borhyaenid species is Arctodictis munizi Mercerat, 1891. 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 anqylosed dentaries at the symphysis; P/p 1 transversely oriented, and m1-3 with a descendent labial lobe on the posterior half of the crown, opening of infraorbitary foramina 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. (4) The non-cursorial adaptations of Arctodictis (e.g. fully plantigrade forelimbs and hindlimbs) and their powerful bone-cracking skulls, allow us to infer ambush hunting behavior, despite the open environments where they lived