Figure 3. Ventral view of the anterior carapace of short-necked turtles showing the bridge-carapace suture (BCS) the rib/gomophosis (R) on pleural 1 (Pl) and their relationship to the vertebral column (V) and the peripherals (Pe).
A-B Elseya lavarackorum Fossil (QM 24121); C-D Emydura subglobosa (UC 0172).

     A significant feature of Emydura lavarackorum, though difficult to quantify, was an indentation of the carapace margin in the area of the cervical cleft and first marginal scutes. This feature is held in common with turtles in the Elseya latisternum group and Pseudemydura, is variable among the Queensland forms of Elseya dentata, and never present in the Northern Territory and New Guinea forms of Elseya dentata nor in Elusor, Rheodytes and Emydura. Although not considered a useful character at generic level, we will use it in combination with other similarities to establish a close relationship between the fossil Emydura lavarackorum and an extant form of Elseya from the Nicholson River.

     The bridge carapace suture runs parallel and adjacent to the rib/gomophosisis in species of the Elseya latisternum group, Pseudemydura and Elusor and so can be clearly distinguished from the fossil Emydura lavarackorum (Table 1). Rotation of the rib/gomophosisis of Pleural 1 eliminates Rheodytes as a possible identification for the fossil, leaving only the Elseya dentata generic group and Emydura as possibilities.

     Two sub-groups within the Elseya dentata generic group can be distinguished. The first comprises Elseya dentata (sensu stricto), Elseya novaeguineae, Elseya branderhorsti, and Elseya sp. (Vogelkopf Region, PNG -- Anders Rhodin, pers. comm) and Elseya sp. (South Alligator River, NT -- Georges & Adams, 1996). The second sub-group is restricted to Queensland (Queensland Elseya dentata sub-group) and comprises Elseya sp. (Nicholson), Elseya sp. (Johnstone), and Elseya sp. (Burnett) (Georges & Adams, 1996). Generic recognition of these sub-groups is not suggested.
     Emydura lavarackorum possesses all characters that are consistent across species of the Elseya dentata generic group (Table 1) and, more significantly, all characters uniquely possessed by the Queensland Elseya dentata sub-group (Table 1). Of those characters which separate Emydura from the Elseya dentata generic group, the fossil consistently possessed character states which distinguished it from Emydura. Therefore, we assign Emydura lavarackorum to the genus Elseya as Elseya lavarackorum (White & Archer, 1994).
     Since the description of Elseya lavarackorum, specimens of the extant Elseya sp. (Nicholson drainage, Georges & Adams, 1996) have become available.