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Neosclerocalyptus Paula Couto (=Hoplophorus = Sclerocalyptus) is a Pleistocene genus of Glyptodontidae Hoplophorini (=Sclerocalyptini) that includes several (ca. twelve) species, many of which have been recognized by typological/morphological taxonomic criteria. Four species have been described for the Ensenadan Stage (early Pleistocene to early-middle Pleistocene) of the Pampean region, Argentina. However, this study shows only two of them to be valid: Neosclerocalyptus pseudornatus and Neosclerocalyptus ornatus. An evident synapomorphy of Neosclerocalyptus is the notable pneumatization and lateral expansion of the fronto-nasal sinuses, which becomes evident in N. pseudomatus (ca. 1.07-0.98 Ma) and even more so in N. ornatus (ca. 0.98-0.40 Ma). This character, interpreted here as a probable response to the cold and arid/semiarid Pleistocene climate, is maximally manifested in the taxa from the middle Pleistocene (Bonaerian Stage) and late Pleistocene (Lujanian Stage). Neosclerocalyptus is very common in the Pampean region and north-central Argentina, but very scarce or absent in the Argentinian Mesopotamia, Uruguay and southern Brazil, areas that were subject to relatively more humid and warmer climates during most of the Pleistocene. From a biogeographical perspective, both Ensenadan species are restricted to the current Pampean region. N. pseudomatus is recorded in the "Toscas" (caliche duricrusts) of Rio de La Plata (Buenos Aires City and Olivos) and Mar del Plata (Buenos Aires province), while N. ornatus is recorded in Mar del Plata and San Pedro (Buenos Aires province), and Granadero Baigorria (Santa Fe province). (C) 2009 Elsevier Ltd and INQUA. All rights reserved.