Ctenophorus decresii
Creators: name: Dong, Caroline M.
name: Johnston, Greg R.
name: Stuart-Fox, Devi
name: Moussalli, Adnan
name: Rankin, Katrina J.
name: McLean, Claire A.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Squamata
Agamidae
Ctenophorus
Ctenophorus decresii

description: Ctenophorus decresii (Duméril and Bibron, 1837)
Tawny Rock Dragon
Figures 1A–C, 4A–B, 5A
Grammatophora decresii (Duméril and Bibron, 1837: 472–
474). Amphibolurus decresii ‘southern race’ (Houston, 1974: 51). Ctenophorus decresii ‘southern lineage’ (McLean et al., 2013:
52).
Types.— The original description was based on two syntypes, a male and a female, from L’Île de Decrès (Kangaroo Island) and registered as MNHN 6545 (Duméril and Bibron, 1837). We designate the male as lectotype (MNHN 6545; Fig. 5A) and the female as paralectotype (MNHN 6545A; Fig. S2; see Data Accessibility) because only the male exhibits the diagnostic coloration.
Diagnosis.— Ctenophorus decresii is a member of the C. decresii species group (Houston, 1974; Houston and Hutchinson, 1998). Within the C. decresii species group, C. decresii is distinguishable by the following combination of characters: snout scales smooth to longitudinally keeled; vertebral scales flat; presence of a broad dark undulating lateral stripe, often constricted into blotches and interrupted to form two separate blotches posterior to the tympanum; and in males, the throat is blue or blue and yellow with yellow to orange margins.
Description.— A moderately sized lizard reaching a maximum SVL of approximately 88 mm and total length of 230 mm. Head and body depressed. Tail long and tapered to a fine tip. Forelimbs moderately long, almost reaching groin when adpressed. Hindlimbs long and reaching or almost reaching snout when adpressed. Finger lengths: 4. 3. 5. 2. 1; toe lengths: 4. 3. 5. 2. 1. Characteristic of the genus, a distinct row of enlarged keeled scales extending from the nostril, below the eye to above the tympanum (Houston and Hutchinson, 1998). Ear membranes exposed and scale-free. Scales on snout are smooth to longitudinally keeled. 12–18 supralabial scales; 11–16 infralabial scales; 4–6 scales between rostral and nasal; 4–6 scales between supralabial and nasal; 10–13 internasal scales; 21–29 subdigital lamellae on the fourth toe (McLean et al., 2013). Dorsal crest is small, no more than a series of keeled scales, becoming smaller posteriorly and not reaching base of tail. Nuchal crest low or absent. Scales on the dorsal surfaces of the limbs and tail are keeled. The gular fold is strongly developed and extends across the shoulders. 40–46 femoral and precloacal pores are arranged in a straight line along the thighs. Pores are present but smaller in females.
Adult male base color varies from gray-blue to brown, with pale blue flanks (Figs. 1C, 4A). The dorsolateral surface of the head is orange to yellow, extending past the shoulders. The extent of this coloration varies among individuals and depends on location but does not extend further than the mid-point of the axilla-groin length. A broad black lateral stripe begins posterior to the tympanum and terminates at the groin (Figs. 1C, 4A). The lateral stripe forms two separate blotches on the shoulder, one circular and enclosed entirely by orange to yellow coloration, while the other is elongated and wraps partly around the other. The remaining length of the lateral stripe is wavy edged or broken. On the ventral surface, males are cream with orange flushes on the belly, hindlimbs, and the length of the tail during the breeding season. A dark chest patch tapers to a point midbody and sometimes extends along the undersides of the forelimbs. This dark patch may vary in intensity, from black to gray. Male throat coloration in mainland populations is ultraviolet-blue with yellow to orange coloration along the gular fold (Fig. 1A); in Kangaroo Island populations, the base blue color is overlain with yellow reticulations (McLean et al., 2014a; Fig. 1B).
Adult females are cryptically colored, predominantly graybrown to orange-brown, densely patterned with darker and lighter speckling (Fig. 4B) and sometimes a thin, pale vertebral line. Similar to males, a black lateral stripe runs along the flanks, similar in shape to that of males but sometimes less prominent. White to cream on the ventral surface. Varying degrees of gray reticulations on the throat, sometimes with a blue tinge. Orange to yellow flushes on the belly and gular region during the breeding season. Juveniles resemble adult females in coloration and pattern. Color patterning remains visible in fresh spirit-preserved specimens but fades with time.
Measurements (mm) and meristic characters of lectotype.— (Bilateral meristics as left [L] and right [R]) SVL, 80; TL, 146.5; AGL, 37; HL, 25; HW, 19.5; HD, 11.5; EYE, 4.7; SL, 9.3; JL, 13.5; NW, 6.5; HUML, 14; RADL, 11.5; HANL, 14; FINL, 10.5; FEML, 17.6; TIBL, 21.3; FOOT, 30.1; TOE, 16.5; SUPRA, 15R/ 14L; INFRA, 18R/17L; ROSNAS, 5R/5L; SUPRANAS, 5R/5L; INTERNAS, 11; SDL, 30R/NA-L; FP, 24R/ 21L.
Distribution and natural history.— Ctenophorus decresii inhabits rocky areas and outcrops, sheltering in rock crevices. The species occurs in the Mount Lofty Ranges, on the Fleurieu Peninsula, and on Kangaroo Island in South Australia, Australia (Figs. 2C, 3A, 6). These lizards occupy temperate habitats with varying levels of vegetation. Adults occur almost exclusively on rocks, perching conspicuously on elevated sites to bask and/or perform territorial and courtship displays. They are active in hot weather and, if disturbed, will run into a crevice or beneath a rock slab.
description: Published as part of Dong, Caroline M., Johnston, Greg R., Stuart-Fox, Devi, Moussalli, Adnan, Rankin, Katrina J. & McLean, Claire A., 2021, Elevation of Divergent Color Polymorphic and Monomorphic Lizard Lineages (Squamata: Agamidae) to Species Level, pp. 43-54 in Ichthyology & Herpetology 109 (1) on pages 46-47, DOI: 10.1643/h2020064, http://zenodo.org/record/7846753