Neosclerocalyptus spp. (Cingulata: Glyptodontidae: Hoplophorini): cranial morphology and palaeoenvironments along the changing Quaternary

Abstract

We propose that the particular high latitudinal distribution of Neosclerocalyptus (Glyptodontidae) and the cyclic nature of the Pleistocene glacial–interglacial events were factors that probably stimulated morphological evolution of its fronto-nasal sinuses, a feature unique among glyptodonts. The distributions of the species, and the majority of its records, are associated with sediments related to arid and semiarid environments. Four species are recognized during the last million years in southern South America. The first record of Neosclerocalyptus (N. pseudornatus) coincides with the “Great Patagonian Glaciation” and shows the lowest grade of pneumatization on its skull. Neosclerocalyptus paskoensis (the most derived species), limited to Oxygen Isotopic Stage 2, shows the greatest development of fronto-nasal pneumatization. The restricted geographic range of Neosclerocalyptus, the possible absence of geographic barriers during the Pleistocene, and the absence of cases of sympatry, allow us to speculate the existence of a single continuous lineage of successive species, showing an anagenetic process.