Diplodactylus furcosus Peters, 1863

Hutchinson, Mark N., Doughty, Paul & Oliver, Paul M., 2009, Taxonomic revision of the stone geckos (Squamata: Diplodactylidae: Diplodactylus) of southern Australia, Zootaxa 2167, pp. 25-46 : 31-33

Diplodactylus furcosus Peters, 1863

Ranges Stone Gecko

Figs. 4 , 5 , 14 B

Diplodactylus furcosus Peters, 1863: 229 . Lectotype ZMB 39231 from Buchsfelde (southwestern outskirts of Gawler), SA ( Fig. 4 ).

Diagnosis. A moderate-sized, longer tailed member of the D. vittatus complex, with strongly scalloped to zigzag vertebral stripe, sometimes a chain of angular blotches, strongly bifurcating on the head and extending as a relatively narrow dark-edged pale stripe to each eye. Flanks with no, small or large pale circular lateral spots. Pale markings thinly outlined in black.

Description ( Figs. 5 , 14 B). SVL 37.0–58.0 mm (mean 50.7, n=30); tailL 22.0–26.0 mm, mean 32.0 (55.2–68.6 % SVL, mean 65.5) (n=21). Supralabials 9–13 (mean 11.3, n=22), the first usually distinctly taller than the second. Infralabials 9–13 (mean 10.5, n=22). Apex of rostral scale with median division descending to about the mid-height of the scale. Supranasals usually in contact; a single internarial present in 5 of 30 examined. 2–4 postnasals (mean 3.3, n=30).

Dorsal colour medium brown, grey-brown or tan. Beige vertebral stripe with strongly scalloped to zigzagged margins, sometimes broken into a chain of angular pale blotches. Vertebral stripe bifurcates on the nape forming a pair of pale stripes, margined with black, terminating at the eye, and leaving an inverted triangular patch of the dorsal colour on the crown and occiput of the head. Blackish paravertebral margins of vertebral stripe prominent but narrow (one to two scales wide) and contrasting sharply with both the light vertebral colour and the medium shade of the upper lateral zone. Upper lateral zone usually well marked with one or more irregular series of small to moderate, well-defined, and sometimes dark-edged circular spots. As with the paravertebral markings, any dark margins of the spots tend to contrast sharply with the adjacent colour. The background colour of the upper lateral zone is uniform, without a peppering of lighter or darker scales. Venter immaculate off-white.

Karyotype. 2n=34, with two large metacentric pairs, the presumed fusion products of chromosomes 3+5 and 4+6 from the 2n=38 karyotype; remainder acrocentric ( King 1977).

Distribution. Southern interior of SA, from the western margin of the Gawler Ranges around Minnipa and Wirrulla, through the Gawler and Middleback Ranges to the Flinders and Mount Lofty Ranges, extending east to the Murray River, and along the northern margin of the Murray into the far west of NSW ( Figs 1 , 16 ).

Similar species. The distribution of D. furcosus abuts or overlaps those of D. vittatus , D. calcicolus sp. nov. and D. wiru sp. nov. Specimens of D. furcosus can be distinguished from sympatric and parapatric specimens of these species as follows: from D. vittatus by the bifurcate head marking and lighter brown colour with the pale markings outlined by narrow but highly contrasting black lines, and longer tail; from D. calcicolus sp. nov. by lack of complex lateral pattern of intermixed dark and light scales and generally a more continuous and boldly outlined dorsal pale stripe. Some specimens of D. calcicolus sp. nov. have continuous dorsal stripes that bifurcate on the head, but these can be distinguished from D. furcosus by having intermixed light and dark scales peppering the flanks, and frequently have a prominent row of very large spots along the flanks where the dorsal colour merges with the ventral colour. Diplodactylus furcosus can be distinguished from D. wiru sp. nov. by the strongly bifurcate occipital marking, rather than pale cap, and narrow, sharply outlined pale dorsal markings, rather than having thick dark outlines that may merge with the dorsal background colour.

Occasional specimens of some other members of the D. vittatus complex can resemble D. furcosus , but the light colouring and sharp narrow black outlines of the dorsal markings usually distinguish D. furcosus . Further distinguished from D. granariensis and D. ornatus by the narrow bifurcation of the stripe towards each eye which has more well-defined inner margins.

Remarks. The holotype of Diplodactylus furcosus (ZMB 39231) clearly preserves the distinctive colour pattern of pale zigzag dorsal stripe narrowly but prominently margined in black and bifurcating on the nape to form well-defined, relatively narrow stripes to each eye. All specimens of the D. vittatus complex occurring within a 60 km radius of the type locality are readily assignable to D. furcosus .

In life most specimens of this species have a light tan background colour, distinctly different in hue to the more grey to greyish-brown dorsal colour of the other southern and eastern members of the complex. In most parts of its range this species is associated with rocky areas or bare stony soils, and there are few records from habitats where the soil is sandy.

Figures

FIGURE 1. Map of southern Australia showing the distribution of the members of the Diplodactylus vittatus species complex described or re-described in the present study. Insets shows details of species distributions in overlap areas in Western Australia and South Australia (See Figs 15 and 16). Diplodactylus vittatus, square; D. furcosus, black cross, D. g. granariensis, circle; D. g. rex, circle with central dot, D. calcicolus sp. nov., grey cross, D. wiru sp. nov., triangle.

FIGURE 4. Lectotype of Diplodactylus furcosus, ZMB 39231. Photo: H. G. Cogger.

FIGURE 5. Variation in colour pattern in Diplodactylus furcosus.

FIGURE 14. Species of the Diplodactylus vittatus complex in life. A, D. vittatus, Warrumbungle Range, NSW, (M. Hutchinson); B, D. furcosus, Whyalla, South Australia (T. Peters, SA Museum); C, D. g. granariensis, Newman Rock, WA (B. Maryan); D, D. g. rex, Wildara Pinnacle, WA (B. Maryan); E, D. calcicolus sp. nov., vicinity of the WA-SA border (G. Harold); F, D. wiru sp. nov. Lake Ifould, SA (P. Oliver).

FIGURE 16. Detail of distribution of D. vittatus complex in South Australia. Note significant range overlap of D. furcosus and D. calcicolus sp. nov. on Eyre Peninsula, and the two regions (arrowed) where three species are sympatric. Symbols as in Fig. 1.