The full range and distribution of the species referred to as C. novaeguineae has only been recently assessed. It is clearly a member of the C. longicollis group based on electrophoresis (Georges and Adams, 1992) and morphology (Rhodin, 1994a,b). Turtles of this group (except C. oblonga) can be identified by the presence of a broad plastron, shorter neck to carapace length ratio and rounded head (sensu Goode, 1967)). They can be further identified by the lack of remnant spurs of the parietal arches, no elongation of the basisphenoid and no elongation of the occipital condyle (Thomson et al., 1997a). Rhodin (1994a) was the first to regard the New Guinean and Australian forms of C. novaeguineae to be different noting that the Australian form (in 3 specimens examined) consistently has paired premaxillary foramina, whereas the New Guinea form usually has a single fused premaxilla and lacked premaxillary foramina. Unfortunately, Rhodin felt he did not have sufficient specimens to form a taxonomic conclusion.
Recent reports of widespread populations of C. novaeguineae across northern Australia (Goode, 1967; Cann, 1972, 1978 ; King & Horner, 1987; Covacevich, et al., 1982; Kennett et al., 1992) has lead to collection and study of these remote populations. We now recognise Australian specimens of what was previously known as C. novaeguineae to be a distinct species, for which we now provide a formal description.
Cann's Longneck Turtle
Chelodina canni sp. nov.
Order Testudines Linnaeus, 1758
Suborder Pleurodira Cope, 1864
Family Chelidae Ogilby, 1905
Subfamily Chelodininae Georges et al., 1998
Type data.- Holotype: NTM 24515; an adult female (carapace length, CL = 215.3mm; carapace width, CW8 = 167.2mm), preserved in alcohol; collected with the help of local aboriginal people at Malogie Waterhole, near Scarlet Hill on
Kalala Station [16° 08' S, 133° 36' E], Northern Territory, Australia by Arthur Georges in April of 1992 (see (Kennett et al., 1992) for a description of the type locality) (Plate 1). Allotype; NTM 24516; a male (CL =150.1mm; CW = 116.8mm) (Plate 1), Paratype: NTM 24517; a female (CL = 208.0mm; CW = 165.7mm), both preserved in alcohol; collection data as for holotype. See Table 1. for comparisons between type specimens and other species, and Appendix 1, for complete list of specimens examined.
Distribution.- C. canni is known from the Roper River drainage (including Maria Island in the Gulf of Carpentaria) in Northern Territory, eastward through the drainages of the Gulf of Carpentaria in north west Queensland. In Cape York it is found in drainages from Cairns in the north down to Rockhampton in the south where a narrow hybrid zone with C. longicollis is found (Georges et al., 2001)(Fig. 1). Hybrids are all recognised by allozymes and by morphology. There are four allozyme markers that separate C. canni and C. longicollis. Hybrids are all heterozygous for these allelles. Thus despite the hybridisation, electrophoretic analysis clearly demonstrates C. canni and C. longicollis are distinct species (Georges et al., 2002). The same 45 turtles tested for allozymes were then looked at to find morphological features that were useful in identifying the hybrids. All hybrids have a deformity of the intergular scute and the underlying bone, they also possess a blend of C. canni and C. longicollis characters.
Diagnosis.- A large species of Chelodina belonging to the C. longicollis group and the C. novaeguineae species complex (see Table 2). Adults can be diagnosed by the wide, rounded carapace with a moderately deep midvertebral trough (Plate 1); a median carapacial keel either absent or minimal, being most observable in the eastern populations; a wide plastron with dark seams on an otherwise uniformly yellow plastron; first and second marginal scutes equal or nearly equal in dorsal surface area; wide head with a red to pink suffusion on the head, neck, and limbs; and bluntly pointed neck tubercles. Hatchlings have an extensive orange-red ventral head, neck, and plastral pattern extending well onto the dorsal aspect of the marginal scutes (Plate 2).