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.

RESUMEN Panochthus Burmeister es uno de los gliptodontes más diversificados y ampliamente distribuidos en el Pleistoceno de Sudamérica, incluyendo zonas situadas a gran altura (>4.000 m s.n.m.). Dentro del género, se reconocen actualmente ocho especies ( 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 y Gillette, y P. florensis Brambilla, López y Parent). Aquí reportamos una coraza dorsal (UATF-V n/n) procedente del Pleistoceno de los alrededores de Potosí, Bolivia, que muestra algunas particularidades morfológicas respecto a las corazas de P. intermedius , P. frenzelianus , P. subintermedius y P. tuberculatus , incluyendo: a) máximo diámetro dorso-ventral situado a la altura de la mitad anterior, mientras que en otras especies se encuentra a la altura del punto medio ( e.g. , Propalaehoplophorus ) o de la mitad posterior ( e.g. , Glyptodon ); b) el perfil dorsal es diferente en comparación con las restantes especies de gliptodontes ( e.g. , Glyptodon , Glyptotherium , Neosclerocalyptus , Propalalehoplophorus ); c) el patrón de ornamentación de los osteodermos muestra una figura central rodeada de pequeñas figuras periféricas poligonales a lo largo de la mayor parte de la superficie expuesta de la coraza (excepto en la región medio dorsal que muestra un patrón de ornamentación reticular), el cual es diferente al de las especies restantes, en las que las figuras centrales se limitan a las regiones caudal, cefálica y más lateral de la coraza. En resumen, la combinación de caracteres sugiere que podría pertenecer a una nueva especie o, alternativamente, a P. floriensis o P. jaguaribensis en las que aún no se conoce la coraza dorsal. El análisis filogenético confirma su posición basal dentro del género Panochthus , lo que evidencia la importancia de estas zonas de gran altitud en los Andes de América del Sur para comprender la compleja historia evolutiva de los gliptodontes.

RESUMO A idade Chapadmalalan (Plioceno) é caracterizada por uma grande diversidade dos Glyptodontidae. A maioria dos táxons é reconhecida a partir de carapaças dorsais parciais e/ou tubos caudais, enquanto que as principais características diagnósticas estão relacionadas com a morfologia particular das superfícies expostas dos osteodermas. Algumas espécies são importantes sob o ponto de vista biogeográfico. O Chapadmalalan Superior é baseado na biozona de Paraglyptodon chapadmalensis. Uma reavaliação do material tipo e referido, aliado a novos achados procedentes das formações Chapadmalal e El Polvorín, indica que a diversidade de Glyptodontidae é menor do que se supunha. A morfologia particular das superfícies expostas dos osteodermas utilizada para a caracterização de algumas espécies na realidade se deve a alterações tafonômicas, que resultaram em um padrão de ornamentação não real. Assim, o Glytodontinae P. chapadmalensis deve ser substituído como fóssil guia, uma vez que nem essa espécie nem as incluídas nos gêneros Urotherium, Trachycalyptus e Lomaphorus são bem caracterizadas. Levando-se em conta a diversidade dos Glyptodontidae para esse intervalo, os Glyptodontinae são muito raros (contrastando com a sua abundância no Pleistoceno), enquanto que Eosclerocalyptus, "Plohophorini" (Plohophorus) e Doedicurinae (cf. Eleutherocercus antiquus) são os táxons mais registrados.

ABSTRACT A large diversity of Glyptodontidae has been proposed as characterizing the Chapadmalalan Age (Pliocene). Most of these taxa were recognized on the basis of partial dorsal carapaces and/or caudal tubes, whereas the main diagnostic characteristic is a particular morphology of the exposed surface of the osteoderms. From a biostratigraphic point of view some species are biostratigraphically important. The Upper Chapadmalalan is based on the Paraglyptodon chapadmalensis biozone. Both the re-evaluation of the type and referred materials and new significant findings from the Chapadmalal and El Polvorín Formations indicate that the diversity of Pliocene Glyptodontidae is more limited than previously supposed. The particular morphology of the exposed surface of the osteoderms that characterizes some of the species actually corresponds to a taphonomic alteration, which results in a non-real ornamentation pattern. Thus, the Glyptodontinae P. chapadmalensis must be replaced as a fossil guide because neither this species nor the species included in the genera Urotherium, Trachycalyptus and Lomaphorus are well characterized. Taking into account the diversity of Glyptodontidae for this lapse, the Glyptodontinae are very scarce (a situation that contrasts with its records in the Pleistocene), whereas Eosclerocalyptus, "Plohophorini" (Plohophorus) and Doedicurinae (cf. Eleutherocercus antiquus) are among the most recorded taxa.