Chelodina oblonga, J. Gray, 1841

Shea, Glenn, Thomson, Scott & Georges, Arthur, 2020, The identity of Chelodina oblonga Gray 1841 (Testudines: Chelidae) reassessed, Zootaxa 4779 (3), pp. 419-437 : 432-433

3.4. Synonymy of Chelodina oblonga , and redescriptions of the type specimens.

3.4.1. Synonymy

Chelodina oblonga J. Gray 1841: 434 , 446.

Chelodina colliei Gray 1856b: 267 . Synonymy by Boulenger (1889).

Macrochelodina oblonga — Wells & Wellington 1985: 9.

Macrodiremys oblonga — McCord & Joseph-Ouni 2007a: 57.

Chelodina (Macrodiremys) colliei — Georges & Thomson 2010: 19.

Chelodina (Macrodiremys) colliei — van Dijk et al. (TTWG) 2014: 430.

Chelodina colliei — Cogger 2014: 243.

Chelodina (Macrodiremys) colliei — Rhodin et al. (TTWG) 2017: 193.

Chelodina colliei — Kehlmaier et al. 2019: 6.

Chelodina (Macrochelodina) oblonga — this study.

3.4.2. Description of type specimens:

Lectotype: BMNH 1947.3.5.89 ( Fig 1 ). Carapace length (straight) = 17.2 cm.

Description. Plastron with three inked markings, on the left humeral scute is the BMNH number “1947.3.5.89”, on the right humeral is the number “74a” Also on the bridge area of the right abdominal is the original number “40.12.9.81”; the latter part of the number is less clear. Dry mounted specimen, entire with the limbs extended. Neck broken, posterior part of neck skin collapsed inside shell. Carapace oval, slightly elongated from above, slightly furrowed along midline, dark brown with a reticulated pattern. 5 th vertebral scute divided along midline; 2 nd marginal scute twice the length of first marginal, all other marginals normal. Plastron narrow and slightly trapezoidal, yellow-orange and highly reticulated. Legs all overstuffed; 4 claws on front and rear feet. Poor condition of neck makes determination of skin characters uncertain, however skin just behind the head finely reticulate with no tubercles observable. Head with artificial eyes inserted, and poorly preserved, though some osseous features visible externally.

Diagnostic comparison. The extreme narrowing and anterior elongation of the shell typical of the south-western Australian species is not obvious; however, carapace shape varies ontogenetically in this species, as apparent from a large series of specimens ranging from hatching to adult examined at the Chelonian Research Institute (CRI). The lectotype fits within the range of carapace shapes of a subadult of this taxon. Plastron length/width at level of axillary notch ratio (P L/W) 2.63, which is comparable with specimens of known Perth provenance (CRI 3129: P L/W = 2.49; CRI 5070: P L/W = 2.56; CRI 4632: P L/W = 2.48), while species of Chelodina (Chelydera) range from 1.88 ( C. expansa CRI 2397) to 2.10 ( C. burrungandjii wolloyarrina ; McCord & Joseph-Ouni, 2009). Frontal region of lectotype skull is narrower than in members of Chelodina (Chelodina) ; however, this character is even narrower in Chelodina (Chelydera) species from northern Australia, due to the anterior rotation and enlargement of the orbits. Postorbitals appear to be narrow and arched, similar to Chelodina (Chelodina) , but differing from Chelodina (Chelydera) which has laterally flattened postorbitals. Posterior part of skull either poorly preserved or damaged, making outline of posterior parietal region difficult to ascertain. The skulls of both subspecies of Chelodina burrungandjii are dorsoventrally flattened, a shape not present in this specimen. Further, the skull of Chelodina burrungandjii burrungandjii is laterally broadened and the palate anteroposteriorly elongated ( Thomson et al. 2000), a configuration also not present in the lectotype. The anterior bridge struts of the Chelodina (Chelydera) species are in general enlarged and encroach to over halfway across the first pleural—this is most extensive in Chelodina expansa and least in Chelodina rugosa ; however this character is absent in the lectotype. Chelodina burrungandjii has an expanded posterior lobe of the plastron at the level of the femoral scutes ( Thomson et al. 2000; McCord & Joseph- Ouni 2007a), a feature not present in the lectotype of C. oblonga , which has a more evenly tapered posterior lobe of the plastron characteristic of the south-western species ( Goode 1967; Cogger 2017). The combination of characters above clearly assigns the lectotype to the Oblong Turtle. Thomson (2000) identified the presence of insertions for an expanded muscular system on the ventral surface of the carapace, only found in the members of the Chelodina B group. It is probable that this was an artefact of preservation as the muscles themselves were long gone, and this character should be considered to have been incorrectly codified at that time .

Paralectotype: OUMNH 02584 ( Figs. 3–4 ). Carapace length (straight) = 27.5 cm.

Description. Plastron with three labels and markings: “Ref. 2584” inked onto left abdominal scute; “ Chelodina oblonga Bell Coll Rev F.W. Hope ” on a label stuck to the left abdominal and pectoral scutes, and “a” in a small label on the left abdominal scute. Dry mounted specimen, entire, with neck and limbs extended. Deep reticulated pattern on the shell typical of the Perth species. 4 th vertebral scute and left 3 rd costal scute divided; nuchal scute wide; 2 nd marginal longer than 1 st; supracaudal scute is offset and deformed; asymmetry of marginal length on the left and right side, though 11 are present on each side; lateral marginals reduced in lateral view. Bridge small, narrow. Plastron dark yellow with no deformities in the scutes. Neck and rear legs slightly overstuffed. 4 claws on front and rear feet. Dorsal surface of neck dark grey, skin finely reticulated, lacking tubercles.

Diagnostic comparison. Carapace elongate and narrow in dorsal view, dorsoventrally flattened in lateral view, medium brown; this combination of features is unique to the Oblong Turtle, the shell shape features are only prominent in adults. Bridge small, narrow. Plastron long, narrow (plastral length/width 2.51, markedly higher than any Chelodina (Chelydera) species). Some features of skull shape are visible due to shrinking of the skin over the skull. Frontal bone and postorbital region narrow, however the frontal is wider than in Chelodina (Chelydera) ; postorbital highly arched as against flat for Chelodina (Chelydera) , see above. Posterior part of parietal elongated and narrow, beginning to expand anteriorly halfway towards orbits, giving a diamond shaped anterior parietal region. Parietal arches, dorsal to quadrates, do not reach supraoccipital, but form cristae that arch dorsomedially. While this specimen has not been genotyped, we believe that morphologically its identification as an Oblong Turtle is without question and genotyping would be for curatorial reasons only, as this specimen is not a name bearing type.

Figures

FIGURE 1. Ventral, left lateral and dorsal views of the lectotype of Chelodina oblonga Gray (BMNH 1947.3.5.89). The lateral image is slightly dorsally angled, affecting the profile of the carapace. (Image courtesy of P. Campbell, BMNH).

FIGURE 3. Dorsal view of the paralectotype of Chelodina oblonga Gray (OUMNH 02584). (Image courtesy of K. Child, OUMNH).

FIGURE 4. Ventral, right lateral and dorsal views of the shell of the paralectotype of Chelodina oblonga Gray (OUMNH 02584). (Images courtesy of K. Child, OUMNH).