The postcranial anatomy of two Middle Devonian lungfishes (Osteichthyes, Dipnoi) from Mt. Howitt, Victoria, Australia

Abstract

The postcranial skeletons of two upper Givetian lungfishes from Mt. Howitt, Victoria, Australia, show remarkable similarities, despite the fact that one is a tooth-plated form (Howidipterus Long 1992) whilst the other has a denticulate dentition (Barwickia Long 1992). Both genera show identical body shape with a short first dorsal fin and greatly elongated second dorsal fin, and small anal fin. The cleithra and clavicles are remarkably similar except for Barwickia lacking external ornament on the lateral lamina of the cleithrum and having a smaller branchial lamina on the clavicle. Both have paddle-shaped subdermal anocleithra that meet the posterior process of the I bone, approximately the same numbers of cranial ribs, pleural ribs, supraneural and subhaemal spines, the same expanded dorsal and anal fin basals with similar number of proximal and middle radials supporting the fins, and approximately the same number of radials supporting the hypochordal lobe of the caudal fin. These numerous similarities in the postcranial skeletons of the two genera strongly suggest that their differing feeding mechanisms probably evolved from a shared ancestral form having a similar postcranial skeleton. Implications for hypotheses of dipnoan phylogeny are discussed. Show more