The osteology and ossification variability of the skull of Antarctic white-blooded fish Chaenodraco wilsoni Regan, 1914 (Channichthyidae, Notothenioidei)

Abstract

A detailed osteological analysis of the skull of an Antarctic fish, Chaenodraco wilsoni Regan, 1914 (Channichthyidae, Notothenioidei) was done, focusing on the bone structure and osteological variability. A notable reduction of the ossification was observed, which took place in several ways: replacement of the whole bone with cartilage, only superficial ossification (e.g. in the ethmoid region), separation of the bones by wide cartilage areas (e.g. in the brain case), and reduction of bone dimensions. An extreme case was complete loss of the opisthootic-the first record of this kind within this family of fishes. The reduction of ossification in Ch. wilsoni resulted in high osteological variability that was observed in the case of reduced bones. Instances of asymmetry of paired elements of the skeleton were observed as well.