The Glyptodontinae (Xenarthra, Glyptodontidae) of the Chapadmalalan Stage/Age (late Pliocene): review and contributions to the knowledge

Abstract

The first records of Glyptodontinae Glyptodontidae come from the Miocene and Pliocene of northern South America (Boreostemma spp.), while the oldest records in southern South America (Argentina) correspond to the “Araucanian” (late Miocene-early Pliocene) (Glyptodontidium tuberifer Cabrera). In this context, the Tertiary taxa of Glyptodontinae from southern South America (“Araucanian”-Marplatan) were scarcely known, and they were limited to a few fragments of the dorsal carapace. More precisely, in the Upper Chapadmalalan Stage/Age (late Pliocene) it is possible to recognise two species: Paraglyptodon dubius Castellanos and P. chapalmalensis (Ameghino in Rovereto); the latter is a guide fossil for this lapse. On the other hand, the “Mesopotamian” (Huayquerian-Montehermosan?; late Miocene-early Pliocene) was characterized by the presence of P. paranensis Castellanos. In this context, the systematic revision suggests that, in the Upper Chapadmalalan, the only valid species is P. chapalmalensis, while P. dubius is a synonym of this. In turn, P. paranensis, (“Mesopotamian”), a taxon represented by a very bad preserved osteoderm of the dorsal carapace, must be considered as a nomen vanum. Finally, we report and describe in this paper the oldest and most complete Tertiary skull of a southern South America Glyptodontinae, here tentatively classified as cf. Paraglyptodon chapalmalensis. Among the most interesting observed characters in this new material it stand out: a) all uper molarifoms (except M1) clearly trilobated; b) narines showing a subtrapezoidal contour; c) the orbits are posteriorly open and freely communicated with the temporal fossae; d) lacrimal tubercle area and orbital notch very similar to that observed in Glyptodon and Paraglyptodon uquiensis; e) skull abruptly truncated by the shortening of the nasals and premaxillae, with a dorsal profile relatively straight and inclined forward.