A peculiar specimen of Panochthus (Xenarthra, Glyptodontidae) from the Eastern Cordillera, Bolivia

Abstract

Panochthus Burmeister is one of the most diversified and widely distributed glyptodonts in the Pleistocene of South America, which includes areas located at high altitudes (>4,000 m a.s.l.). Within the genus, eight species (P. intermedius Lydekker, P. subintermedius Castellanos, P. tuberculatus (Owen), P. frenzelianus Ameghino, P. greslebini Castellanos, P. jaguaribensis Moreira, P. hipsilis Zurita, Zamorano, Scillato-Yané, Fidel, Iriondo and Gillette, and P. florensis Brambilla, López and Parent) are currently recognized. Here, we report a dorsal carapace (UATF-V n/n) from the Pleistocene of the surroundings of Potosí, Bolivia, that shows some morphological particularities when compared to the carapace of P. intermedius, P. frenzelianus, P. subintermedius and P. tuberculatus, including: a) its maximum dorso-ventral diameter is at the anterior half, meanwhile in other species is at mid-point (e.g., Propalaehoplophorus) or at posterior half (e.g., Glyptodon); b) the dorsal profile is different in comparison to other glyptodonts (e.g., Glyptodon, Glyptotherium, Neosclerocalyptus, Propalaehoplophorus); c) the ornamentation pattern of the osteoderms shows a central figure surrounded by small polygonal figures along the most exposed surface of the carapace (except for the mid-dorsal region that shows reticular ornamentation pattern), being different from that of the remaining species: of Panochthus, in which central figures are limited to the caudal/cephalic and most lateral regions of the carapace. In summary, the combination of characters suggests that it could belong to a new species or, alternatively, to P. floriensis or P. jaguaribensis in which the dorsal carapace is not yet known. The phylogenetic analysis confirms its basal position among Panochthus and highlights the importance of these high elevation areas of the Andes in South America in order to understand the complex evolutionary history of glyptodonts.