Comparative Morphometry of Bactrian Camel and Dromedary

Abstract

There are two living species of Old World camelids (Camelidae, Artiodactyla): the Bactrian camel (Camelus bactrianus) and the dromedary (Camelus dromedarius). Differences in osteology between them are poorly known, and this lack of knowledge hinders archaeological and paleontological research. Previous comparative studies have focused on subtle qualitative differences, which are subject to great intraspecific variation and interspecific overlap. In this study, we use simple morphometric methods and statistical analyses to compare the skeleton of Old World camels. Over the entire skeleton we were able to find several consistent differences, some univocal and highly diagnostic, others only slightly significant and noticeable only at a population level. Some of the distinctive traits are suggestive of previously unknown biological adaptations. In particular, the cranial anatomy of Bactrian camels shows characters correlated with increased grazing, while its limb muscle attachments may indicate additional need for lateral stability in a heavier animal. The presence and number of humps is reflected in the vertebral column, with several differences that will be helpful in the reconstruction of fossil species.