Redescription of the gnathostome fish fauna from the mid-Palaeozoic Silverband Formation, the Grampians, Victoria

Gnathostome vertebrate remains from fine-grained sandstones of the Silverband Formation in the Grampians, Victoria include dissociated fin spines, scales and teeth. These elements arc assigned herein to the acanthodians Sinacanthus? micracanthus (fin spines) and Radioporacanthodes sp. cf. R. qujingensis (scales and tooth whorls). This fauna indicates a Late Silurian (?late Ludlow) age for the vertebrate-beating Stratum. Under current systematic groupings, the two gnathostome taxa from the Silverband Formation belong to two different families, the Sinacanthidae and the Poracanthodidae. However. the preserved association could indicate that the three element types derived from the same biological species. The possibility that the Sinacanthidae is a sister group to the Climatiidae and the Poracanthodidae is raised by this scenario. The Sinacanthidae is tentatively reassigned to the Acanthodii, as it is considered to lack diagnostic chondrichthyan characters.