Fitzinger, 1826
Snake-necked turtles
Recognition
Chelodina includes the 11 semi-aquatic, long-necked chelid turtles of Australia and New Guinea. The adult carapace is flattened, oval to elliptical, usually has a smooth marginal rim, and lacks a vertebral keel. A vertebral groove is often present. A small cervical scute is present and the 1st vertebral scute is broader than the 2nd. Usually neural bones are absent, but in C. oblonga up to eight may occur. The plastron is rigid and either large and broad, almost completely covering the carapacial opening, or long and narrow. Axillary buttresses are strong while those of the inguinal are weak and extend only to the 5th costal bones. The intergular scute is large, but usually lies behind and does not separate the gular scutes. However, it does separate the humerals and anterior portion of the pectorals. The cervical vertebrae are longer than those beneath the carapace. A temporal arch is lacking in the skull, so the parietal does not contact either the quadrate or supraoccipital bones. Nasal bones are separated by the anterior process of the frontal; prefrontals are only narrowly exposed along the dorsal margin of the external nares. Frontal bones are fused. Beneath the cranium there is extensive quadrate-basisphenoid contact, and the vomer and palatine meet. The jaws lack ridges on the triturating surface, and the upper jaw is not hooked. The lower jaw lacks an external horny sheath. The toes are webbed, and there are four claws on each foot.
Remarks
Burbidge et al. (1974) divided the genus into three groups as follows:
(1) neck comparatively short and thin; skull small, not flattened (height/width of the skull at rear of maxillae < 1: 2.5); carapacial neurals usually absent (Rhodin and Mittermeier, 1977, showed Chelodina novaeguineae may have up to four neurals on occasion); carapace length of adult female <25 cm—Chelodina longicollis, Chelodina mccordi, Chelodina novaeguineae, Chelodina pritchardi, Chelodina reimanni, Chelodina steindachneri.
(2) neck very long and thick; skull large and flattened (height/width > 1: 2.5); carapacial neurals absent; carapace length of adult female >25 cm—Chelodina expansa, Chelodina parkeri, Chelodina rugosa, Chelodina siebenrocki.
(3) neck very long and thick; skull large and flattened (height/width > 1: 2.5); five to eight neurals present in carapace; carapace length of adult female >25 cm—Chelodina oblonga (Goode, 1967, includes this species in group 2, but, in addition to having no neural bones, the shells of those species are deeper and more heavily built than that of C. oblonga).
Wells and Wellington (1985) partitioned the genus Chelodina into Chelodina (longicollis, and novaeguineae), Hesperochelodina (steindachneri), and Macrochelodina (expansa, oblonga, rugosa, and siebenrocki), but these changes have not been accepted.
Undescribed Species
A yet undescribed Australian species cf. Chelodina rugosa is found in rivers and streams of the Arnhem Land and the Kimberley sandstone escarpment (Chelodina sp (Arnhem Land)). The sandstone snake-necked turtle has an oblong, black carapace and its skin is black with brown patches; the Kimberley population may have brown-pinkish spots along the underneck and in the foreleg cavity. Rather exceptionally for the genus, the Arnhem Land population is known to take vegetarian matter. John Cann (pers. comm.) reports the Kimberley and Arnhem Land populations may eventually turn out to be separate forms.
Cann (1997d) very recently described a snake-neck turtle from Kalumburu, Western Australia—Chelodina kuchlingi (Chelodina kuchlingi). It is separated from the forementioned Chelodina by a round head (wedge-shaped in the sandstone long-neck) and an oval, fawn-colored carapace. To date only a single specimen of this species is known (Cann, 1997d).
Chelodina sp; Chelodina sp 2; Chelodina sp 3; Chelodina sp 4 (close-up of head); Chelodina sp 5 (plastron) is an undescribed New Guinean species closely related to Chelodina reimanni. Hans-Dieter Philippen is working on a description.
Species identification
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