Osteology of vertebral column and caudal skeleton of nemacheilid loaches, genus Paraschistura from Iran (Teleostei: Nemacheilidae)

These small loaches are distributed from the upper Tigris River basin to Pakistan. Currently a total of 16 species are recognized in Iran. Since osteology has proven to be a useful tool for studying the taxonomy and phylogeny of fishes, including loaches, we have studied some osteological characters are studied in 13 species from Iran. To conduct this study, the fishes were fixed in 10% formaldehyde, stored in 70% and then deposited in the Zoological Museum, Collection of Biology Department, Shiraz University. Digital X-ray radiographs were taken from the left side of all fish using a Faxitron Bioptics. Based on the obtained results caudal skeleton consists of five or six hypurals and unpaired epural, parahypural and pleurstyle bones. The pleurstyle is fused to the last centrum. The shape of the epural is varies in each species. The fifth hypural is triangular, not connected to the terminal centrum and different in size. The results revealed that some Paraschistura species can be distinguished based on the caudal complex, especially by the number of hypurals, dorsal- and caudal-fin rays and the number of vertebra. Therefore, it seems that specific characters, are more useful in distinguishing higher taxa such as lineages, genera and families rather than individual species.