Diporiphora bilineata Gray, 1842

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 : 41-42

Diporiphora bilineata Gray, 1842

Common name. Two-lined dragon.

Figure 15 , Tables 3, 4

Diporiphora bilineata Gray, J.E. 1842 . Description of some hitherto unrecorded species of Australian reptiles and batrachians. Pp. 51–57 in: Gray, J.E. (ed.). The zoological miscellany. Treuttel, Würz & Co: London. [54]. Type data: syntype (s) – BMNH 1946.8.12.75–76, Port Essington , NT.

Diagnosis. Body size moderate (to 58 mm SVL) with long tail (2.2–2.7 × SVL). Gular and post-auricular folds absent, scapular fold present but weak. Granular scales in axilla, extending over arm to neck. Dorsal scales moderately heterogeneous: scales on 2nd paravertebral row and the two rows of pale dorsolateral scales slightly enlarged and raised. Flanks dark in colour with dark colour of granular scales extending posteriorly onto flanks, which have a speckled appearance due to scattered white scales on the dark background. Pre-cloacal pores 2; femoral pores 0.

Description of syntypes. Males; 57 and 58 mm SVL, 151 and 56 (broken) mm tail length. Medium-sized Diporiphora , moderately gracile with long limbs and long tail. One canine on either side of upper jaw. Gular and post-auricular folds absent, scapular fold present. Dorsal scales heterogeneous; vertebral row of scales, plus the 3–4 rows immediately adjacent on either side, are enlarged and strongly keeled. The vertebral row and the fourth longitudinal scale row from the vertebral are raised. Beyond these enlarged vertebral scales are four rows of small homogenous scales and then a dorsolateral longitudinal row of enlarged scales, with scales on each side strongly keeled. Raised vertebral and dorsolateral scale rows extend up onto neck onto the back of head and posteriorly onto tail. Scales on flanks homogeneous, although changing from small granular scales in axilla to small but non-granular scales on the posterior two-thirds of flanks. A few small pale spinose scales at back of head on each side, lacks spinose scales on limbs or tail. Granular scales in axilla, extending over arm onto neck. Ventral scales strongly keeled. Pre-cloacal pores 2; femoral pores 0.

Dorsum strongly patterned. Wide pale, poorly defined vertebral stripe associated with enlarged vertebral scale rows and narrow pale dorsolateral stripes associated with row of enlarged scales, extending from back of head onto base of tail. Six dark transverse bands between head and pelvis, narrower than the pale background. Head relatively plain with little patterning, labials similar colour to rest of head and lacking pale line between eye and ear. Dark smudge on posterior of tympanum absent. Flanks dark in colour with dark colour of granular scales extending posteriorly onto flanks, which have a speckled appearance due scattered white scales on the dark background. Lateral stripe between axilla and groin absent. Dark patch in axilla extending up onto shoulder. Arms and legs lack dark banding. Faint banding on hind limbs; dark bands down length of tail, with dark bands being wider than the light bands. Ventral surface cream with no patterning.

Variation. 46–58 mm SVL; 113–156 mm tail length. Tail long, ranging from 2.2–2.7 × SVL. Gular fold always absent and scapular fold present in all animals examined. In a few specimens a small post-auricular fold present. Outer raised trailing edge of scales on outer row of dorsolateral stripes usually present but often trailing edge of scales are only weakly raised, providing demarcation between dorsal and lateral surface. Pre-cloacal pores 2; femoral pores 0.

Variable patterning from strongly patterned to plain individuals. In patterned individuals, 5–7 dark brown transverse bands ranging from narrower to wider than pale background. Dark bands are offset to each other on either side of a narrow greyish or cream vertebral stripe and intersected two pale dorsolateral stripes. In plain individuals, dark dorsal transverse bands are faint or absent, vertebral stripe may be absent but there are usually still the pale dorsolateral stripes from neck to at least level of mid-dorsum. However, dorsolateral stripes are also absent in a few animals. Granular scales on flanks around arm are usually dark brown, extending posteriorly onto flanks that have speckled appearance due to scattered white scales on a dark background. These scattered pale scales sometimes form vertical lines. No white markings on face, labial scales speckled with light brown flecks. Usually faint or no banding on legs but in some more patterned animals banding present. Ventral surface cream, usually plain but some individuals have faint longitudinal stripes on ventral surface of head. Males with breeding colouration tend to lose some of their dorsal patterning, having a yellow wash over the head and upper body with a large black patch in axilla that extends onto shoulder.

Distribution and ecology. Diporiphora bilineata is widely distributed across the Top End of NT. It occurs sympatrically with D. magna in the Pine Creek area. It is a common generalist that occurs throughout the tropical savannah woodlands and grasslands of this region, and is often seen perching on low vegetation, rocks or termite mounds.

Comparison with other species. The distribution of D. bilineata overlaps with two other Diporiphora species. Diporiphora bilineata can be distinguished from D. magna in usually having fewer pre-cloacal pores (2 vs. 4), lacking a post-auricular fold and by possessing heterogeneous dorsal scales, rows of enlarged vertebral scales and dark flanks with scattered white scales. Diporiphora bilineata can be distinguished from D. sobria in lacking a gular fold and femoral pores, and having single canines on either side of the upper jaw.

Remarks. This taxonomic revision has reduced the distribution of this species to the Top End of the NT, with overlap with D. magna in the Pine Creek area. Previously, adult males of D. bilineata in breeding colouration may have been mistaken for D. magna , and D. jugularis has been resurrected that was often attributed to D. bilineata , further reducing this species’ range. Genetic work has shown that these two species do not overlap extensively ( Smith et al., 2011).

Figures

Figure 15. Diporiphora bilineata: a, adult in non-breeding colours, Casuarina, Northern Territory (photo: S. Wilson); b, syntypes BMNH 1946.8.12.75–76, Port Essington, Northern Territory.