Evolution and zoogeography of Australian freshwater turtles

The contemporary turtle fauna of Australia comprises freshwater and marine species but no terrestrial taxa. The literature on evolution and zoogeography of the Australian freshwater turtles (Chelidae) is reviewed. Because opposing conclusions were reached in several of these studies, we critically examine each of them. We accept the phylogeny of Georges & Adams (1992); Elseya and Emydura are not synonymous and Elseya consists of the E. dentata and E. latisternum species groups (generically distinct). However, Pseudemydura umbrina shares common ancestry with other Australian short-necked turtles and is their extant sister taxon. The E. latisternum group is the sister taxon of the noti-Pseudemydura Australian short-necked turtle genera. Understanding pre-Cretaceous dispersal of the ancestral lineage on the South American-Antarctic-Australian supercontinent is important for ascertaining relationships among Australian freshwater turtles. Increasing aridification during the Pleistocene, resulting in isolation within river drainages, appears to have augmented allopatric speciation. We recognize 23 extant species of Australian chelid turtles in 7 genera: Chelodina expansa, C. longicollis, C. novaeguineae, C. oblonga, C. rugosa, C. steindachneri and one undescribed species; Elseya dentata and 3 undescribed species; Elseya latisternum and three undescribed species; Elusor macrurus; Emydura macquarrii (inclusive of E. australis, E. krefftii and E. signata), E. subglobosa, E. victorias and 2 undescribed species; Pseudemydura umbrina; and Rheodytes leukops. Relationships among genera remain enigmatic