Added 24 April 2026.
Two striking-looking arboreal lizards from South America. Both are believed to be canopy dwellers. Avila-Pires (see Bibliography) has more details.
Boulenger gives the characteristics of the genus as follows: tympanum distinct. Body depressed; no dorsal crest; dorsal scales small, imbricate, uniform. Upper head scales little enlarged. Two transverse gular folds; no gular pouch. Digits compressed, bent at the articulations, with keeled lamellae inferiorly. No femoral pores or preanal pores. Tail short, flat, with whorls of spinose scales. Lateral teeth tricuspid; no pterygoid teeth. A large sternal fontanelle. No abdominal ribs.
Bartlett & Bartlett advise against the keeping of these species because of their diet, which is mainly composed of ants. Likewise Bosch and Werning state that U. azureum does not do well in captivity for this reason.
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Scientific Name |
Common Name |
Distribution |
Size |
Notes |
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Uracentron |
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U. azureum |
Green Thornytail Iguana |
Colombia, Guyana, Suriname, French Guiana, Brazil |
TL approx 12.5 cm, SVL approx 8 cm |
Description: snout short, broadly rounded, lips somewhat swollen; nostril turned upwards; upper head-scales small, with small granular asperities; a series of slightly dilated transverse supraoculars; occipital a little longer than broad, narrower than the supraocular region; 5-6 upper and 6-7 lower labials; ear-opening moderate, its anterior border without denticulation. Sides of neck irregularly plicate; a strong transverse gular fold, and a second, less regular, in front. Lateral and anterior dorsal scales very small, granular, smooth ; posterior dorsal scales larger, subrhomboidal, obtusely keeled; ventrals larger, squarish, imbricate, smooth; > 86 scales around midbody, and >110 scales along a middorsal line (from nape to posterior margin of hind limbs); Digits slender. The adpressed hind limb reaches the shoulder or slightly beyond. Tail: moderately depressed, shorter and narrower than the body, flat inferiorly, about twice as broad as deep, with whorls of very large, obtusely keeled spinose scales, the spines strongest on the sides; less than 25 dorsal rows of caudal scales from base to tip of tail. Coloration: azure blue or olive above, with crescentic black cross bands; lower surfaces greenish or yellowish. [SOURCES: Avila-Pires, Bartlett & Bartlett, Boulenger] |
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U. a. azureum |
As for species description, plus the following characteristics: (1) body moderately depressed. (2) Tail mostly wide (fig. 62). (3) Ventrals relatively numerous (57-72). (4) Dorsal surface of tail mostly with 7, rarely 8, scales in a transverse row at its widest point. (5) Suture of nasal with postrostral/lorilabial series anterolateral or lateral (fig. 63). (6) Supraoculars with 3-4 rows of scales of similar width, or some of the scales moderately to much larger than the others; laterally there are mostly three rows of small scales anteriorly, diminishing to two or one posteriorly; row adjacent to supraciliaries with rectangular, flat scales. (7) Scales on nape smooth or broadly keeled. Dorsals, in some specimens, smooth in the light areas, keeled in the black bands, keels larger toward sacrolumbar region. In other specimens dorsals become keeled posteriorly, irrespective of colour of scales, and either all posterior scales, or only the scales in middorsal area are keeled. (8) Scales on antero-dorsal aspect of upper arms very feebly keeled (almost smooth) to slightly keeled; on posterior aspect of forearms (at least near elbow) slightly keeled; on dorsal aspect of thighs very feebly, slightly, or distinctly keeled; on antero-dorsal aspect of lower legs distinctly to strongly keeled; elsewhere smooth. Coloration: body with several crescent-shaped dark bands, from posterior margin of head to at least middle of body. One large dark spot on each supraocular area. An anteriorly oriented dark arc on interparietal, in contact with an arc along posterior margin of head. [SOURCE: Avila-Pires] |
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U. a. guentheri |
E Peru, NW Brazil |
As for species description, plus the following characteristics: (1) body moderately depressed. (2) Tail wide, and tending to be slightly shorter than in U. a. azureum and U a. werneri (table 7). (3) Ventrals relatively numerous (57-68). (4) Dorsal surface of tail with 7-8 (sometimes 9) scales in a transverse row at its widest point. (5) Suture of nasal with postrostral/lorilabial series anterolateral (fig. 63). (6) Supraocular region with 3-4 longitudinal rows of larger scales; one of these rows may have very wide scales occupying most of supraocular area, or anteriorly two of the rows have scales slightly wider than, to twice as wide as, those in the other rows, and some much wider scales are present only posteriorly. Row of rectangular, flat scales adjacent to supraciliaries totally or partially separated from the large supraoculars, anteriorly, by small, irregularly polygonal scales; posteriorly mostly in contact with the large supraoculars. (7) Scales on nape smooth or with a broad, weak keel; posterior dorsals smooth to distinctly keeled. (8) Scales on antero-dorsal aspect of upper arms smooth to very feebly keeled; on postero-dorsal aspect of forearms feebly to slightly keeled (stronger toward elbow); on dorsal aspect of thighs slightly keeled; on antero-dorsal aspect of lower legs distinctly keeled; elsewhere smooth. Coloration: body with a reticulate pattern; some crescent-shaped dark bands may be present on neck and anterior part of body. Head irregularly spotted. [SOURCE: Avila-Pires] |
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U. a. werneri |
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Colombia, Venezuela |
As for species description, plus the following characteristics: (1) Body cylindrical to slightly depressed. (2) Tail relatively narrow (fig. 62). (3) Ventrals less numerous (50-63) than in U a. azureum and U a. guenteri. (4) Dorsal surface of tail with 7 (sometimes 8) scales in a transverse row at its widest point. (5) Suture of nasal with postrostral/lorilabial series mainly anterior (fig. 63). (6) Supraocular region with scales in 4-6 approximately longitudinal rows, of which 1-2, especially in the posterior half of supraocular area, with slightly to distinctly wider scales. Rectangular, flat scales adjacent to supraciliaries in contact with posterior wide supraoculars, and partially or totally separated from anterior supraoculars by small, irregularly polygonal scales. (7) Scales on nape mostly convex and smooth, sometimes broadly keeled or slightly but distinctly keeled. Posterior dorsals from smooth and flat, to slightly convex with a very weak, broad keel. (8) Scales on postero-dorsal aspect of forearms and on antero-dorsal aspect of thighs smooth to weakly keeled; on antero-dorsal aspect of lower legs weakly to distinctly keeled; elsewhere smooth. Coloration: body, in preservative, uniformly coloured or with a (usually faint) reticulate or mixed pattern, in the latter case partially reticulate, partially with broken, irregular, transverse lines. Head dorsally spotless, except for a pair of dark spots (usually approximately oval, occasionally irregular) on interparietal. [SOURCE: Avila-Pires] |
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U. flaviceps |
Tropical Thornytail Iguana |
Colombia, Ecuador, Peru, Brazil, poss. Bolivia |
TL approx 17 cm, SVL approx 10.5 cm |
Description: upper head-scales very convex. Dorsal scales small, rhomboidal, imbricate, strongly keeled, increasing in size posteriorly; lateral scales smaller; ventrals as large as dorsals, feebly keeled; 68-85 scales around midbody, and 81-98 scales along a middorsal line. Tail: quite flat, nearly as broad as the body, lanceolate; caudal scales large, rhomboidal, forming longitudinal and transverse series, strongly keeled, spinose, the spines strongest on the sides; more than 30 dorsal rows of caudal scales from base to tip of tail. Otherwise as in the preceding species. Coloration: black, uniform (males) or with numerous round greenish spots and the lower surfaces greenish-white or pale olive; upper surface of head sometimes yellowish. [SOURCE: Avila-Pires, Boulenger] |