Characterisation of shell shape in species of Elseya (Pelocomastes). A Ovoid shell of Elseya (Elseya) branderhorsti (ANWC R08292) overlaid on the holotype of Elseya (Pelocomastes) albagula (QM 81785) to illustrate the lateral expansion of the anterior peripheral associated with marginal scutes M1 and M2 (“squaring off”). In the largest individuals of Elseya (Pelocomastes) this expansion leads to the development of a nuchal bay, whereby the most anterior points of the carapace are associated with marginals M2, with marginals M1 recessed to a point at their juncture (in the absence of the cervical), a feature of the fossil holotype of Elseya lavarackorum. Scale applies to Elseya branderhorsti. B Aged specimen of Elseya (Pelocomastes) lavarackorum (Boodjamulla National Park, Qld); C Aged specimen of Elseya (Pelocomastes) irwini (Johnstone River, Qld). Photos A: Arthur Georges; B: Alastair Freeman; C: Ivan Lawler.