New sirenian fossils from the Middle Eocene of the Pamplona Basin (Navarrre).

Abstract

New sirenian remains from the Eocene of the Pamplona Basin (Navarre) are described, extending the record of these mammals into the western Pyrenees. The fossils were collected in two outcrops, Uztarrotz and Ardanatz, which are located near the city of Pamplona, displaying different lower Bartonian lithostratigraphic units (Pamplona Marls and Ardanatz Sandstone). The remains are well preserved and consist of vertebrae and ribs, showing the robustness and compact structure of pachyosteosclerotic bone, which is typical of but not exclusive to sirenians. From morphological and biometrical points of view, the vertebrae and ribs from the Pamplona Basin are comparable to the sirenian remains from several Eocene localities of the Pyrenees and other areas of the Mediterranean Tethys, which have been referred to several species of Prototherium. Some specimens are also similar to those of Halitherium taulannense from the Priabonian of Provence. However, the vertebrae from Navarre are more robust than, and exhibit other differences relative to, the genus Protosiren from the southern margin of the Tethys. The morphological, biogeographical and chronological evidences suggest that the sirenian remains from the Pamplona Basin belong to a basal dugongid close to Prototherium.