Diporiphora bennettii (Gray, 1845)

MELVILLE, JANE, DATE, KATIE SMITH, HORNER, PAUL & Doughty, Paul, 2019, Taxonomic revision of dragon lizards in the genus Diporiphora (Reptilia: Agamidae) from the Australian monsoonal tropics, Memoirs of Museum Victoria 78, pp. 23-55 : 36-37

Diporiphora bennettii (Gray, 1845)

Common name. Kimberley sandstone dragon.

Figure 11 , Tables 3, 4

Gindalia bennettii Gray, J.E. 1845 . Catalogue of the specimens of lizards in the collection of the British Museum. British Museum: London. xxviii+289 pp. [247]. Type data: holotype – BMNH 1946.8 .12.77, “ N.W. Coast of Australia ”.

Diagnosis. Small body size (to 55 mm SVL) and short tail (<2.0 × SVL), with robust habitus and wide head with short snout. Gular fold present, post-auricular fold strong, scapular fold weak. Dorsals homogeneous, scales in axilla not granular. Lacks dorsolateral stripes. Usually lacks dark smudge on tympanum, although some individuals have a faint dark spot on posterior edge of tympanum. Pre-cloacal pores 2; femoral pores 0.

Description of holotype. Female; 50 mm SVL; 68 mm tail length. Small body size with wide head and short wide neck. Two canines on either side of upper jaw. Gular fold present. Strong post-auricular fold, weak scapular fold. Post-auricular fold with 1–3 spines. Dorsal scales mostly homogeneous, strongly keeled with keels parallel to midline forming lines running longitudinally down dorsum from shoulders to one third of the way down the tail; enlarged scales associated with vertebral or dorsolateral stripes are absent. Scales on flanks homogeneous, with keels angled towards dorsum. Lacks spinose scales on limbs or tail. Scales in axilla not granular. Weakly keeled scales on ventral gular region and strongly keeled scales on ventral torso. Pre-cloacal pores 2; femoral pores 0.

Dorsum patterning faint and diffuse. Lacks vertebral or dorsolateral stripes. Lacks visible dark transverse bands between head and pelvis. Head virtually unpatterned, without pale labials or pale line between eye and ear. Faint dark spot on posterior of tympanum. Flanks similar to dorsum, with sides of torso being slightly darker than dorsum with a few light brown spots. Lateral stripe between axilla and groin absent. Lateral dark spot absent. Very faint banding on lower hind limbs, dark banding on tail, with light bands much wider than darker bands. Arms lack dark banding. Ventral surface of head, torso and tail unpatterned and cream colouration.

Variation. 41–55 mm SVL, 53–83 mm tail length. Tail short, less than 2.0 × SVL. Gular fold ranges from weak to strong, always with reduced scales along fold, even if skin does not fold over; post-auricular fold strong and scapular weak. Head triangular with usually pronounced adductor muscles, snout short. Typically, one or two enlarged spinose scale above tympanum and on post-auricular fold, with 0–3 adjacent slightly enlarged scales. No conspicuous nuchal crest, but occasionally slightly raised scales present. Dorsal scales homogeneous with no abrupt demarcation of dorsal and lateral scale sizes. Keels of scales on sides angled dorsally and posteriorly. Scales above cloaca on sides of tail at base with raised keels. Tail short, terminating in a blunt tip.

Background colour an admixture of dark brown, tan and pale white scales generating a rather diffuse background pattern with no highly contrasting dorsolateral stripes. Dark brown cross-bands obscure, but in some heavily marked individuals they can form loose networks that enclose pale spots. In some individuals, especially juveniles, there are alternating wide dark brown blotches and thinner pale lines along the dorsum, although these are usually interrupted by variable admixture of different-coloured scales. Lateral surfaces tend to be darker with pale stippling. Tails with thin dark bands with wide pale interspaces. Usually lacks dark spot on tympanum. Ventral surface pale with occasional dark stippling on chin, sometimes extending to ventrum.

Distribution and ecology. Restricted to the northern Kimberley (fig. 8), with many records from the Mitchell Plateau and Prince Regent River National Park, extending east to Drysdale River National Park and including a few neighbouring offshore islands: Augustus, Darcy and Unwins.

Collection records (over 40) are nearly all from sandstone rock outcrops and escarpments with spinifex cover.

Comparison to other species. This species is similar to D. perplexa sp. nov., with extensive distributional overlap and occurring in similar habitats, but differs in having a much smaller body size, a short tail and no dorsolateral stripes. It differs from D. albilabris in having a smaller body size, a short tail, no femoral pores, homogeneous dorsal scales and in pattern by lacking any prominent vertebral or dorsolateral stripes. It differs from D. magna and D. margaretae in having a smaller body size, a short tail, a gular fold and a pair of enlarged canines on each side of upper jaw. It differs from D. pallida sp. nov. in having two canine teeth on each side of upper jaw.

Remarks. The species was previously believed to include what we describe below as D. perplexa sp. nov. Diporiphora bennettii , however, is the sister species to D. albilabris (fig. 1b; also restricted to the northern Kimberley), with these two being sister species to D. sobria , which is now understood to be widely distributed in the southern AMT. D. perplexa sp. nov. occurs over a broad area in the Kimberley and extends to the NT, and accordingly, D. bennettii is now known to be restricted to the north-west Kimberley. Diporiphora bennettii has an unusual morphology for a Diporiphora , owing to its small body size, short tail, robust habitus, obscure dorsal patterning and close association with sandstone outcrops in the northern Kimberley. The redefinition of this species and reduction of its range adds to the large number of endemic reptiles and frogs from this region (e.g. Powney et al., 2010; Palmer et al., 2013).

Figures

Figure 11. Diporiphora bennettii: a, adult from Little Mertens Falls area, Mitchell Plateau, Western Australia. (photo: S. Wilson); b, holotype BMNH 1946.8.12.77, from the “NW coast of Australia”, showing dorsal view.