3.2.3. Subgenus: Chelodina (Chelydera) subgen. nov. Thomson and Georges, this study.

Type Species: Chelodina parkeri Rhodin & Mittermeier 1976 .

Diagnosis: Large riverine turtles; carapace broadly oval with noticeable flaring about marginal scutes 8–10; plastron narrow, covering only about half of the anterior orifice of the shell in ventral view; plastron of moderate length, approximately twice as long as its width measured anterior to the bridge; head and neck longer than carapace; intergular scute rhomboid in shape with width approximately equal to length. Neck dorsum finely reticulated, lacking obvious tubercles. Osteologically, atlas (C1) elongated; cervical vertebrae 2–4 greatly elongated (centrum about three times as long as wide); transverse processes of cervical vertebrae thickened, not bladelike as in subgenera Chelodina and Macrochelodina . Skull dorsoventrally flattened, in some species also laterally expanded, resulting in antero-posterior enlargement of palatines. Hyolaryngeal assemblage highly modified; extreme elongation of corpus hyoideum along sulcus tracheae; anterior cornubranchiale expanded, elongated, extending beyond posterior cornubranchiale; epibranchials fully ossified in adults, cartilaginous throughout life in species of the other subgenera. Anterior bridge struts enlarged; suture with pleural 1 extends half-way across pleural; proximal suture of strut enlarged and also contacts 2 nd pleural in very large specimens; posterior bridge strut enlarged and thickened, but does not contact pleurals; ilium sutures with 8 th pleural and pygal and is latero-posteriorly rotated. Exposed neural bones usually absent (except for Chelodina burrungandjii, typically with 3–6 exposed neurals; Smales 2019). Fluid from ducts in the inguinal and axillary pockets with noticeable odour, but not pungent.

Etymology: The name Chelydera is a combination of the Greek χέλυς/χέλυδρος (chelys/chelydros), meaning both a turtle (cf. the similarly snake-necked turtle genus Chelus Duméril 1806) and a water snake, and δειρή (deire), the neck (f.) (Liddell & Scott 1897; Brown 1956). This is in reference to the common name for this group, the snakenecked turtles. We use a feminine name for the subgenus to agree with Chelodina, to avoid a change in gender of any adjectival specific epithets if Chelydera is treated as generically distinct by some authors.

Assigned Species: C. parkeri Rhodin & Mittermeier 1976; C. burrungandjii Thomson, Kennett & Georges 2000; C. expansa Gray 1857; C. kuchlingi Cann 1997; C. rugosa Ogilby 1890; † C. insculpta De Vis 1897; † C. alanrixi Lapparent de Broin & Molnar 2001 . Vernacular name: Australasian snake-necked turtles