Ctenophorus decresii (DUMÉRIL & BIBRON, 1837)
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Ctenophorus decresii
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| Higher Taxa | Agamidae (Amphibolurinae), Sauria, Iguania, Squamata (lizards) |
| Subspecies | |
| Common Names | E: Tawny Crevice-dragon, Tawny Dragon |
| Synonym | Grammatophora decresii DUMÉRIL & BIBRON 1837: 472 Agama decresiensis FITZINGER 1843: 83 (nom. subst. pro G. decresii) Ctenophorus decresii — FITZINGER 1843: 83 Amphibolurus decresii — BOULENGER 1885: 385 Amphibolurus decresii — COGGER 1983: 110 Amphibolurus decresii — GIBBONS & LILLYWHITE 1981 Ctenophorus decresii — MANTHEY & SCHUSTER 1999: 47 Ctenophorus decresii — COGGER 2000: 312 Ctenophorus decresii — WILSON & SWAN 2010 Ctenophorus decresii — CHAPPLE et al. 2019: 59 |
| Distribution | Australia (South Australia) Type locality: Kangaroo Island, South Australia. |
| Reproduction | oviparous |
| Types | Syntypes: MNHN-RA 6545, MNHN-RA 6545A, Ile Decrès, SA, collected Péron & Lesueur. |
| Diagnosis | Diagnosis (genus): Very small to moderately large agamids with body slightly compressed to strongly depressed; tympanum exposed (except in C. maculosus); a series of enlarged tectiform scales sweeping up in a flat S-curve from below eye to above ear; and mostly with (1) dorsals small, their keels directed back towards midline; (2) numerous femoral and pre-anal pores, each located between 4 scales (anterior usually largest; (3) alignment of pre-anal pores directed forwards towards midline; and (4) black markings on breast and throat of males (STORR 1982). 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 (Dong et al. 2021). 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 gray-brown 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 (Dong et al. 2021). For a comparison of species across the decresii complex, see Dong et al. 2021. |
| Comment | Synonymy: COGGER 1983 listed modestus as a synonym of decresii but Dong et al. 2021 revalidated Amphibolurus modestus AHL 1926, which also restricted decresii to the southern populations. Not listed in COGGER 1983, but he lists Amphibolurus decresiensis (in error ?). Status of the latter name unclear. Distribution: Not in NSW; all NSW records are now Ctenophorus mirrityana. See Dong et al. 2021 for a map in South Australia. Type species: Grammatophora decresii DUMÉRIL & BIBRON 1837 is the type species of the genus Ctenophorus FITZINGER 1843. Grammatophora DUMERIL & BIBRON 1837:468 is a nomen substitutum pro Gemmatophora KAUP 1827; non Grammatophora STEPHENS, a nomen nudum and a genus of Lepidoptera). Variation: Ctenophorus decresii exhibits remarkable variation in coloration both within and among populations, inlcuding sexual dichromatism (Houston, 1974; Teasdale et al., 2013; McLean et al., 2013). Ecology: for a phylogenetic analysis of ecological adaptations in Ctenophorus see Tallowin et al. 2019, Gibbons 1981. Amphibolurus decresii is found on rocks which are predominantly pinkish yellow, whereas A. vadnappa is found on rocks which are dark reddish brown Habitat: saxicolous. Group: the Ctenophorus decresii complex consists of four closely related, rock- inhabiting species: C. decresii (Duméril & Bibron 1837), C. fionni (Procter 1923), C. tjantjalka Johnston 1992, and C. vadnappa (Houston 1974). All species are sexually dimorphic with cryptically coloured females and larger, brightly coloured males which perform conspicuous courtship and territorial behaviour (Gibbons, 1979). Overall body form is highly conserved within the group and reflects adaptation to rocky habitats; all species have dorsoventrally flattened heads and bodies (less so in C. tjantjalka) and long hindlimbs (Houston & Hutchinson, 1998). While females and juveniles are similar in appearance among species, male coloration is an obvious distinguishing feature between species (Houston, 1974), and is likely to be an important social signal within the C. decresii complex (Osborne, 2005; Stuart-Fox & Johnston, 2005, McLean et al. 2013). |
| Etymology | named after an island, “Ce Grammatophore a été trouvé par Péron et Lesueur, dans l'île de Decrès, en Australasie” (Duméril & Bibron, 1837: 474). |
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