Diversity and phylogeny of the Glyptodontidae (Xenarthra, Cingulata) from the Chasicoan Stage/Age (late Miocene) of Argentina

BARASOAIN, DANIEL; ZURITA, ALFREDO; TOMASSINI, RODRIGO; CONTRERAS, VICTOR

Buenos Aires

Otro; 1° Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina; 2020

Asociación Paleontológica Argentina

A great diversity of Glyptodontidae (Xenarthra, Cingulata) has been mentioned for the Chasicoan Stage/Age (late Miocene), particularly in the Pampean region of Argentina, including representatives of the tribes Palaehoplophorini, Plohophorini, and "Sclerocalyptini". In this contribution, we carried out a detailed revision including the most complete specimens known for this lapse: 1) PV-UNS-260, from Arroyo Chasicó Formation (Buenos Aires Province), composed of fragmented skull, almost complete dorsal carapace, caudal tube with first ring, and right femur; and 2) PVSJ-366 from Loma de Las Tapias Formation (San Juan Province), composed of almost complete skull, dorsal carapace fragments and caudal rings. Both specimens develop dorsal carapaces with a uniform ornamentation pattern (?rosette pattern?) and a similar caudal tube morphology. Additionally, other specimens of this lapse are mainly represented by isolated osteoderms, which also show the same ornamentation pattern. Our comparative study suggests, contrary to the high diversity previously mentioned, the presence of a single morphotype for this lapse, which would represent a new taxonomic entity that, for the moment, cannot be assigned to the known tribes.This better anatomical characterization allowed to include Chasicoan glyptodonts into a morphological phylogentic analysis for the first time. Obtained results place them as sister group of all the following Neogene and Quaternary diversity, condition supported by the development of a unique caudal tube morphology, representing the first appearance of some derived characters in this structure, such as peripheral figures and lateral figures increasing their size towards the apex.