Revision of the cranial anatomy of Ophisaurus acuminatus Jörg, 1965 (Anguimorpha, Anguidae) from the late Miocene of Germany

ABSTRACT The anguine species Ophisaurus acuminatus Jörg, 1965 is known on the basis of only one specimen consisting of skull bones and osteoderms from the late Miocene (MN 9) Höwenegg/Hegau locality in Germany. Since its first description, several other new species of Ophisaurus Daudin, 1803 have been described from various Miocene localities in Europe. The diagnoses of these new species are based mostly on characters on the parietal and partially frontal bones. Although most of the cranial elements of O. acuminatus are well preserved, its parietal is absent. The knowledge of the detailed anatomy of this anguine species is crucial for the understanding of its interrelationship within the genus Ophisaurus. For our re-study of this specimen we used a high-resolution X-ray microcomputed tomography. The application of this method enabled: 1) to reveal the anatomy of not visible portions of the previously described bones; 2) to discover the bones completely or almost completely embedded in the sediment; and 3) to identify previously not determined skull bones. Our study enabled to identify three distinguished features for this species and confirmed the validity of the species O. acuminatus.