A reassessment of the phylogenetic position of the family Cobitidae (ostariophysi)

Abstract

The m. adductor mandibulae of members of the Cobitidae and of representatives of other ostariophysean taxa is dissected and a cladistic analysis of the muscle characters is carried out. A peculiar anterior belly of the adductor mandibulae is observed as unique to and shared by the cobitids, the homalopterines and the gastromyzonines. It is concluded that the presence of this muscle belly demonstrates that these three taxa comprise a monophyletic assemblage and this is identified as the cobitoid group. From variation in the anatomy of the adductor mandibulae within the cobitoid group it is hypothesised that,contrary to the traditionally held belief, the botine leaches probably constitute the most phylogenetically advanced lineage of the cobitoids and that the Botini and the Cobitini together form the advanced sister-group of the Noemacheilirii, Homalopterini and Gastromyzonini. The osteology of the two unusual cobitid-like bornean taxa Ellopostoma and Vaillantella is described. A comparative study of cobitoid osteology is carried out subsequent to the myology. It is concluded that Ellopostoma is probably more closely related to the Homalopterini than to anything else and that Vaillantella is probably more closely related to the Noemacheilini than to anything else. It is further concluded that there are no osteological characters to refute unequivocally the novel hypothesis of cobitoid intrarelationships made available from the myological study.