Scelidotheriine (Mammalia, Xenarthra, Mylodontidae) autopodial bones from the Late Pliocene of the La Cruz Valley, Province of Córdoba, Argentina

Resumen

Here we report new associated autopodial remains (Chapadmalalan) of La Cruz valley, near La Cruz, Córdoba Province. The remains include metacarpals III–V, a digit III abaxialpalmar sesamoid, and a metatarsal V, stored at Museo de Paleontología, Universidad Nacional de Córdoba. The bones areslightly larger than in pre-Chapadmalalan scelidotheriines (Proscelidodon), but quite smaller than in Pleistocene related taxa(Valgipes, Catonyx, and Scelidotherium). A multivariate analysis using autopodial measurements clearly separates the newspecimen from Pleistocene scelidotheriines. As in Scelidotherium, the metacarpal III proximal end is not dorsally prominent,unlike Proscelidodon gracillimus. As in Catonyx, the articular surface for metacarpal IV in metacarpal III faces less distallythan in Valgipes. The metacarpal IV shaft is, as in Scelidotherium, dorsopalmarly depressed, unlike Catonyx. Body size inference,based on proportions of more complete Pleistocene scelidotheriine specimens, suggests that the new finding is withinthe size range of Proscelidodon patrius, but not other Chapadmalalan scelidotheriines. We performed a phylogenetic analysis,adding five new characters to a published data matrix that includes 31 manual characters. This analysis supports close relationships of CORD-PZ 3953 with Scelidotherium. Therefore, the systematic position of the new specimen most closelyapproaches Scelidotherium parodii than other Chapadmalalan scelidotheriines. This raises the possibility that CORD-PZ 3953represents the oldest known autopodial bones assignable to this genus, maybe belonging to the species Scelidotheriumparodii. Study of Montehermosan–Chapadmalalan autopodial material associated with skulls or mandibles will be necessaryto test these hypotheses.