Comparative Osteology of Two Far Eastern Species of Ratsnakes (Serpentes: Colubridae), Elaphe dione (Pallas, 1773) and E. schrenckii (Strauch, 1873), for the Purpose of Palaeontological Studies

The taxonomic identification of Quaternary remains requires a comparison of fossil bones with the skeletons of existing taxa based on the morphological criteria. However, the osteology of most modern snake species has not yet been studied. This work is aimed at finding differences in the bone morphology of Amur and Dione's ratsnakes and the criteria for their identification. The variety of bone morphology depends on several parameters. First, these are species differences which determine the systematic position of the animal. Second, it is individual variability.Third, these are progressive changes in the vertebrae morphology along the vertebral column from the first vertebra to the last. Fourth, it is age-related variability. 20 skeletonised specimens: 12 specimens of Elaphe dione and 8 specimens of Elaphe schrenckii were used to define diagnostic osteological characters. The bones of the two studied species are very similar and their variability overlaps. However, differences and identification criteria were found for 13 skull bones:nasal, frontal, parietal, supraoccipital, maxilla, quadrate,palatine, pterygoid, ectopterygoid, basiparasphenoid,basioccipital, dentary and the compound bone. In addition, the variability and differences of the cervical,trunk, cloacal, and caudal vertebrae were examined.