The species of Eutatus (Mammalia, Xenarthra), assessment, morphology and climate

KRMPOTIC, C. M., CARLINI, A. A, SCILLATO-YANÉ, G. J

QUATERNARY INTERNATIONAL

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2009 vol. 210 p. 65 - 75

1040-6182

a b s t r a c t From a systematic perspective, the genus Eutatus is in a complex situation. P. Gervais published the type species, Eutatus seguini. Later, F. Ameghino recognized Eutatus brevis, Eutatus punctatus and Eutatus minutus, whose diagnostic characters were not clearly defined. A.F. Bordas added a new species, Eutatus ameghinoi, and provided anatomical differences between this species and E. seguini, but did not compare it with the others previously recognized by Ameghino. For these reasons, Scillato-Yane´ only recognized for the Ensenadan, Bonaerian and Lujanian stages the type species E. seguini and synonymized the other four. On the other hand, E. seguini has been mentioned as occurring, if not exclusively, in the Ensenadan stage. However, an exhaustive review of earlier publications indicates that E. seguini is the Eutatus species occurring in the Bonaerian, Lujanian and Platan (middle Pleistocene to early Holocene) stages. Osteoderm characters, as well as endoskeletal elements, were compared between specimens assigned to the previously nominated species. A detailed analysis of osteoderms from homologous regions of the pelvic shield (internal and external morphology) was performed to identify significant differences that would allow recognition of the eventual species of this genus. Materials from the Chapadmalalan, Marplatan (Vorohuean), Ensenadan and Lujanian stages were selected. An equivalent comparative study was made on the osteoderms of Chaetophractus villosus (Euphractinae, Euphractini) to assess the range of intraspecific morphological variations. Differences were found between osteoderms from different stratigraphical provenance. According to the new nomenclatural situation proposed here, E. seguini is limited to the Bonaerian, Lujanian and Platan stages, and a new species is recognized for the Marplatan (Vorohuean, Sanandresian) and Ensenadan stages. The morphological changes in osteoderms of different Eutatus species may be correlated with paleoclimate variations, because these changes consist of variations in the amount and extension of cavities that would have held hair follicles and the development of cavities that would have been filled with adipose tissue, probably acting as thermal insulation.