A large predator from the late Oligocene of Patagonia (Mammalia, Metatheria, Sparassodonta)

FORASIEPI, A.M.; BABOT, J.; ZIMICZ, N.

Zapala-El Chocón

Jornada; XXVIII Jornadas Argentinas de Paleontología de Vertebrados; 2014

The large sized Deseadan sparassodont Pharsophorus(?) antiquus (Ameghino) was to date only represented by isolated teeth. Initially this species was referred to the genus Borhyaena Ameghino, but later it was assigned to Proborhyaena Ameghino and then re-assigned to Pharsophorus(?) Ameghino. Here we describe and analyze an almost complete but fractured skull (UNPSJB-PV 113 ?Universidad Nacional de la Patagonia ?San Juan Bosco?) from the late Oligocene (Deseadan SALMA), Cabeza Blanca, Chubut Province, Argentina. We compare with the holotype and referred ?Ph.(?)? antiquus material and identify UNPSJB-PV 113 as belonging to this species. In our phylogenetic analysis ?Ph.(?)? antiquus is grouped with Arctodictis and Borhyaena in the Borhyaenidae, but not with Pharsophorus lacerans Ameghino, the type species of this genus. Compared to Arctodictis Mercerat and Borhyaena, UNPSJB-PV 113 and the existing ?Ph.(?)? antiquus molars have broader stylar shelf on M3 and ectocingulum extending backwards up to the metacone, better developed talonid in lower molars, and a distinct metaconid on m2?m4, more separated from the talonid. Under our phylogenetic hypothesis, homoplasies are detected within borhyaenoids on the lower molars: the metaconid is usually lost within Sparassodonta but retained in Pharsophorus and borhyaenids on m2?m4 or m2?m3. The short snout, large canines, deep jaw, reduced protocones and talonids determine ?Ph.(?)? antiquus as hypercarnivorous. The deeply vaulted skull, well-develop temporal fossa, little difference on the jaw depth at p3 and m4 are suggestive of bone-cracker specializations. ?Ph.(?)? antiquus is within the largest Deseadan sparassodonts with a body mass of about 70 kg.