A new Late Devonian acanthodian fish from Mt. Howitt, Victoria, Australia, with remarks on acanthodian biogeography.

A new acanthodiform acanthodian, Howittacanthus kentoni gen. et sp.nov. is described from the Frasnian lacustrine Mt. Howitt site, eastern Victoria. Howittacanthus is characterized by: a palatoquadrate ossified in three divisions with both otic and auxiliary otic cotyli in contact with the brain-case; autopalatine with posterior basal process; slender body form with small pelvic fins closer to anal than to pectoral fins; and all fin-spines ornamented with a single ridge. Ontogenetic data obtained from Howittacanthus agree with the findings of Zidek for Acanthodes. The family Acanthodidae is redefined. Howittacanthus is placed as the possible sister taxon to a group containing Acanthodes and Acanthodopsis by shared characters of the jaw cartilages. A Euroamerican centre of origin is proposed for acanthodiforms, gyracanthids and diplacanthoids. These groups probably entered the East Gondwana Province following faunal interchange with the Eurameican Province sometime in the Middle Devonian.-Author