Scelidotheriine (Mammalia, Xenarthra) autopodial bones from the Pliocene (Chapadmalalan) of Córdoba province, Argentina, and their systematic implications

Here, we report new autopodial material belonging to a scelidotheriine sloth from the Pliocene (Chapadmalalan) of Rio de La Cruz valley, Córdoba province, Argentina. The epiphyseal suture fusion in metacarpals III and IV indicates adult size; compared with other scelidotheriines, the preserved bones are slightly larger than in pre-Chapadmalalan taxa, but quite smaller than in post-Chapadmalalan taxa. The metacarpal III presents a distal carina longer relative to proximodistal length – from proximalmost point of proximal end to centre of carina – than in other scelidotheriines. The metacarpal IV shaft is dorsoventrally depressed, as in post-Chapadmalalan specimens of the genus <i>Scelidotherium</i>. Differences from the latter include a metacarpal III with a mostly saddle-shaped articular surface for metacarpal IV, and a metatarsal V with a strongly raised surface on the proximal end plantar surface. A phylogenetic analysis including 13 scelidotheriine and 5 outgroup terminals, and 173 characters supports close relationships with <i>Scelidotherium</i>. The size of the presently reported specimen likely matches the size range of material previously assigned to <i>Scelidotherium parodii</i>. The specimen probably represents the first autopodial remains reported for a Pliocene representative of that genus and raises the possibility that it belongs to the Chapadmalalan taxon, <i>Scelidotherium parodii</i>.