Osteology of Ronquilus jordani (Zoarcoidei: Bathymasteridae), with a discussion of the developmental osteology and systematics of bathymasterid fishes.

The zoarcoid family Bathymasteridae contains seven species in three genera (Bathymaster, Rathbunella, Ronquilus) found in the North Pacific Ocean. Although several synapomorphies have been identified for the family, molecular analyses recover the family as a paraphyletic grade. The goals of this study are to provide a description of the skeleton of R. jordani as a baseline contribution for future systematic comparisons among all bathymasterid taxa and zoarcoids. We used our osteological study to discuss ontogenetically variable characters that appear to carry phylogenetic signal within Zoarcoidei. Finally, we discuss the systematic relationships of Bathymasteridae, including its monophyly and their systematic relationships. The vertebrae of Bathymasteridae develop in two distinct patterns. In Ronquilus and Bathymaster, the vertebrae initially form in the mid‐caudal region and development proceeds both anteriorly and posteriorly until the entire vertebral column is complete. In contrast, in Rathbunella the vertebrae initially form immediately posterior to the skull and development proceeds posteriorly; this is interpreted to be plesiomorphic. Other characters that were clarified (e.g., presence of well‐developed teeth on the gill rakers of Ronquilus) or described (e.g., variation in fusion caudal skeleton elements across Zoarcoidei) now must be evaluated in a taxonomically comprehensive systematic analysis of Zoarcoidei. [ABSTRACT FROM AUTHOR]