Redescription of the pectoral fin and vertebral column of the rhizodontid fish Barameda decipiens from the lower carboniferous of Australia

ABSTRACT

The original description of the pectoral fin of the rhizodontid Barameda decipiens emphasized the narrowness of the fin, based on a narrow radius and low number of preserved lepidotrichia. Elements of the vertebral column were said to be most similar to the tristichopterid Eusthenopteron. A more complete description of the pectoral fin and vertebral column of Barameda, based on new silicone molds and X-rays, indicates that the fin is much wider than previously estimated and that the radius has a morphology more comparable to that of other rhizodontid taxa. Branching occurs both in the lepidotrichia of the distal fringe of the fin, and at the distal end of the more proximal elongate and unjointed basal elements. The latter branching may be restricted to Barameda and Gooloogongia among the Rhizodontida. Branching and jointing appear to be greater in the trailing edge of the fin, enhancing flexibility in this region. Newly described features of the humerus include the distal groove housing the entepicondylar foramen. The fin element previously identified as the ulnare is reinterpreted as a branchial element (hypobranchial) and a portion of the scapulocoracoid can be recognized. Ten rhachitomous intercentra are preserved, similar to those of Eusthenopteron in possessing well-developed parapophyses, but differing in the presence of these parapophyses on all preserved vertebrae, believed to represent the anterior vertebral column in Barameda.