Comparative osteology of Bathylutichthys balushkini and relationship of the family Bathylutichthyidae (Cottoidei)

Abstract

The structure of skeleton of Bathylutichthys balushkini was studied and comparative analysis of it with representatives of other families of the suborder Cottoidei was performed. It was found that Bathylutichthyidae are characterized by the presence of a great number of original characters supporting its family status. They include: absence of mesethmoideum; bony canals of seismosensory system on frontale, pteroticum, and parietale and their strong reduction on infraorbitale; and absence of pterosphenoideum, intercalare, pharyngobranchiale 2, and basihyale. At the same time, Bathylutichthyidae retain a considerable number of generalized specific features: location of parietalia laterally to supraoccipitale and absence of their joint between themselves, presence of mesoptergoideum and basibranchialia 2 and 3. Cladistic analysis based on osteological characters and characters of the seismosensory system of 11 families of Cottoidei demonstrates that Bathylutichthyidae are combined into one group with families Rhamphocottidae, Agonidae, Psychrolutidae, Cyclopteridae, and Liparidae occupying an intermediate position between Psychrolutidae and the two last families. The cladogram obtained does not support the point of view of existence in the suborder Cottoidei of an independent superfamily Cyclopteroidea, including families Liparidae and Cyclopteridae.