A redescription and reinterpretation of Gyracanthides murrayi Woodward 1906 (Acanthodii, Gyracanthidae) from the Lower Carboniferous of the Mansfield Basin, Victoria, Australia

ABSTRACT

The articulated acanthodian Gyracanthides murrayi Woodward from the Lower Carboniferous of Mansfield, Victoria, Australia, is redescribed from original and newly aquired material. It includes the only known head region from a member of the Gyracanthidae. A new reconstruction and interpretation of the pectoral area are proposed, incorporating the elements from the original description as well as a new bone interpreted as a procoracoid attached to a prepectoral spine. The posterior free pectoral spine described by Woodward is reinterpreted as a scapulocoracoid. A subsequent reconstruction of the pectoral girdle which synonymised the anterior and posterior prepectoral spines is rejected. A clear difference in size and shape of the pectoral and pelvic fin spines is established. The morphology of the tubercular ornament of the paired fin spines is used to distinguish species of Gyracanthides. Gyracanthides murrayi had a covering of dermal polyodontodia with spinose crowns and a concave base with a central vascular canal opening.

The systematic position of the Gyracanthidae remains unclear, with the family retained within the Climatiiformes only on the basis of the broad-based, fin spines with nodose ornament.