Pelocomastes de Vis, 1897 sensu Thomson et al. (2015)

Thomson, Scott A., Friol, Natalia R., White, Arthur, Wedd, Dion & Georges, Arthur, 2023, The Australian gulf snapping turtle Elseya lavarackorum (Testudines: Chelidae) revisited-Is the late Pleistocene fossil species extant?, Vertebrate Zoology 73, pp. 237-256 : 237

Subgenus: Pelocomastes de Vis, 1897 sensu Thomson et al. (2015)

Type species.

Pelocomastes ampla (= Elseya [ Pelocomastes ] Elseya uberrima de Vis, 1897 sensu Thomson 2000, Thomson et al. 2015).

Included species.

Elseya (Pelocomastes) albagula Thom-son, Georges & Limpus, 2006 sensu Thomson et al. (2015), Elseya (Pelocomastes) irwini Cann, 1996 sensu Thomson et al. (2015), Elseya (Pelocomastes) lavarackorum (White & Archer, 1994: 159) sensu Thomson et al. (2015) and Elseya (Pelocomastes) nadibajagu Thomson & Mackness, 1999) sensu Thomson et al. (2015).

Field identification.

Although many of the external characters are highly variable and thus not diagnostic when considered individually, it is possible to provide guidance for the identification of extant Elseya (Elseya) dentata and Elseya (Pelocomastes) lavarackorum . This is particularly important where they occur in sympatry (e.g. the Roper River, NT, Georges et al. 2021). The typical features that distinguish the two are shown in Figs S2-S4. Elseya (Pelocomastes) can be distinguished from Elseya (Elseya) by the presence of extensive lingual ridges in addition to the alveolar ridges on the rhamphotheca; an intergular scute that moderately separates the humerals, at most half (half or more in Elseya (Elseya) ; serration of the rear of the carapace that extends into adulthood; and departure from the classical ovoid shape of the carapace (typified by Elseya (Elseya) , Fig. 6 ) by squaring off of the anterior carapace in Elseya (Pelocomastes) leading ultimately to a nuchal bay in the largest, oldest individuals (Fig. 6 ). Elseya (Pelocomastes) lavarackorum can be further distinguished from Elseya dentata by the presence of red flushing on the undersurface of the limbs and on the feet (Fig. S3), and the reticulate patterning of the temporal region of the head, fading with age (Fig. S3). If genotyping is available (e.g. DArTcap, Guppy et al. 2020), the distinction between the two (and between Elseya [ Pelocomastes ] Elseya lavarackorum and Elseya [ Elseya ] Elseya flaviventralis ) is definitive ( Georges et al. 2021).

Figures

Figure 6. Characterisation of shell shape in species of Elseya (Pelocomastes). A Ovoid shell of Elseya (Elseya) branderhorsti (ANWC R 08292) overlaid on the holotype of Elseya (Pelocomastes) albagula (QM 81785) to illustrate the lateral expansion of the anterior peripheral associated with marginal scutes M 1 and M 2 (" 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 M 2, with marginals M 1 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.