On the phylogenetic position of Gogonasus andrewsae Long 1985, within the Tetrapodomorpha

Abstract

AbstractWithin the Tetrapodomorpha, the Late Devonian Gogonasus andrewsae of the Gogo Formation, Gogo, Western Australia, has occupied an uncertain phylogenetic position. Following the description of several well‐preserved three‐dimensional skulls and pectoral girdles, the discovery of the first complete specimen (NMV P221807) made Gogonasus one of the best‐known tetrapodomorph fish. Recent studies of pectoral fin structure and the spiracular opening of Gogonasus have suggested an unexpected affinity with ‘elpistostegalid’ fish such as Tiktaalik. Subsequent work has refuted characters linking these taxa, with phylogenetic analysis of the Tetrapodomorpha placing Gogonasus basal to megalichthyids and tristichopterids. In this paper we reanalyse characters linking Gogonasus with ‘elpistostegalid’ fish and those supporting the placement of Gogonasus crownward of Eusthenopteron. New phylogenetic analyses of the Tetrapodomorpha show a revised phylogenetic position of Gogonasus as being deeply nested within the Tetrapodomorpha, crownward of Osteolepis and Megalichthys, but basal to Eusthenopteron+‘elpistostegalids’. Functional consideration of the spiracular structure suggests a position of Gogonasus closer to ‘elpistostegalids’, although data is lacking from other less‐well‐preserved taxa to fully test the hypothesis. The humerus of the Late Devonian lungfish Chirodipterus from Gogo, Western Australia is figured for comparative purposes.