Evolution of dipnoans (lungfish) in the Early Devonian of southeastern Australia

Abstract

Dipnoans (lungfish) were first described from the Lower Devonian at Taemas N.S.W. in 1906 with the discovery of a species now known as Dipnorhynchus suessmilchi (Etheridge). Subsequent descriptions were based on material from Wee Jasper in N.S.W., Buchan in Victoria and from the Snowy Mountains region of N.S.W. A new genus, Speonesydrion Campbell & Barwick, 1984, has since been described from Wee Jasper and Taemas. No other genera have been described from southeastern Australia (the Molong-Monaro Terrane of Yolkin et al. 2000). A new genus Cathlorhynchus is described from the Currajong Limestone Member. Near the top of the sequence, a large genus described as Dipnorhynchus cathlesae by Campbell & Barwick (1999), has now been placed in a new subgenus Dipnorhynchus (Placorhynchus). Examination of overseas occurrences indicates that there was no immigration of other dipnoans into southeastern Australia in the Early Devonian, hence, we consider that the collective Dipnorhynchus-Speonesydrion lineages must have evolved locally. This evolutionary pattern provides an opportunity to discuss localized evolution within a distinctive group through the Emsian.