First occurrence of Janospira from the Early Ordovician of Australia

Cavanosteus, a new genus of homostiid arthrodire, with C. australis (McCoy) as type species, is erected for new material from the Early Devonian (Emsian) of the Burrinjuck area, NSW. This new material compares closely with the holotype from Buchan, Victoria, identified as the central plates from the skull; it includes lower jawbones (infragnathals) lacking denticulation also closely similar to those of Homostius from the Middle Devonian of the Baltic Province and Scotland. The only bone from the dermal trunk armour referred to the new genus is an anterior dorsolateral plate. Relationships of other large Early Devonian arthrodires assigned to the family Homostiidae are discussed. Cavanosteus gen. nov. is probably the closest relative to the type genus known from the Early Devonian.