 This was culminated in a reanalysis of the morphological data which demonstrated the convergence of the clades on a sweep of distinctive features needed for their piscivorous diets, Thomson, 2000.The subfamilies within Chelidae show the monophyly of the majority of the South American species and all the Australian species, with the far more ancient "Hydromedusa" as sister taxon to both these other groups.The family Chelidae contains about 60 species within around twenty genera