Genus Urosaurus – Brush- and Tree Lizards

QUICK INDEX

U. auriculatus, Socorro Island Tree Lizard

U. bicarinatus, Tropical Tree Lizard

U. clarionensis, Clarion Island Tree Lizard

U. gadovi, Gadow's Tree Lizard

U. graciosus, Brush Lizard

U. irregularis, Mexican Brush Lizard

U. lahtelai, Baja California Brush Lizard

U. microscutatus, Small-Scaled Lizard, Small-Scaled Uta

U. nigricaudus

U. ornatus, Tree Lizard

Scientific Name

Common Name

Distribution

Size

Notes

Urosaurus

U. auriculatus

Socorro Island Tree Lizard

Mexico (islands of Socorro and Revillagigedo in Colima)

Enlarged antero-dorsal femoral scales smooth

U. bicarinatus

Tropical Tree Lizard 

SE Mexico (Sonora, Sinoloa, Nayarit, Michoacán, Guerrero, Puebla, Morelos, Oaxaca, Chiapas, Jalisco, Aguascalientes)

U. b. bicarinatus

??

Mexico (Michoacán, C Guerrero, Puebla, Morelos)

U. b. anonymorphus

Mexico (E Guerrero, Oaxaca and W Chiapas)

U. b. nelsoni

Mexico (Oaxaca)

U. b. tuberculatus

Mexico (S Sonora, Sinaloa, Nayarit, Jalisco, Colima)

U. b. unicus

Mexico (Chihuahua) 

U. clarionensis

Clarion Island Tree Lizard

Mexico (islands of Clarion and Revillagigedo in Colima)

U. gadovi

Gadow's Tree Lizard

Mexico (Michoacán, Jalisco)

U. graciosus

Brush Lizard

USA (SE California, S Nevada, SW Arizona), Mexico (NE Baja California, NW Sonora)

SVL 2¾-3½”/4½-6½cm; tail 2¼-2½x SVL

Found in bushes and small trees, especially creosote, often motionless and pointing downwards. Hunting is done on the ground but the species does not remain there for long; however, holes and burrows are utilised both for refuge and for hibernation. Brush Lizards can change colour quite rapidly, this being partly thermal related. Scalation details: frontal divided; median, longitudinal area of enlarged scales from just before shoulders to tail, where it merges with large dorsal caudals; some of the scales in the median area may be slightly smaller; all scales across rump of nearly equal size except those immediately bordering the legs; distinct granular fold, overlapped by larger scales. Other: 9-14 femoral pores; enlarged postanals present in males; postfemoral pocket regularly absent; unregenerated tail is at least twice body length. Coloration: dorsally light grey to grey-brown; head finely patterned with fine dark lines; 8-10 narrow dark grey transverse bands on body to midlateral area, usually coinciding in position either side but not always; transverse band above shoulder often more conspicuous and darker than the rest; pale line, usually poorly defined, and sometimes bordered above by a dark line, from supralabial area to above arm and thence to the groin; vague dark and light streaks usually present on neck; dark line runs from rear of eye above tympanum to neck and may continue posteriorly on a dark line above the lateral light line; ventral surfaces slightly dusky in females, sometimes with short dark streaks on chest and belly, males usually having somewhat streaked throat [Smith], or both sexes may have a reddish, orange or lemon yellow throat [Stebbins]; pale to navy-blue patches on either side of belly from axilla to near groin, these patches becoming more extensive with age and darker in large specimens; small light white or blue flecks dot the blue patches, becoming very noticeable in old specimens; blue areas on either side are separated by width of 2-4 scales. Reproduction: 1 (poss. 2) clutches of 2-10 eggs laid May-August [SOURCES: Smith, Stebbins]

U. g. graciosus

U. g. shannoni

U. irregularis

Mexican Brush Lizard

Status unclear: see Reptile Database entry.

U. lahtelai

Baja California Brush Lizard

Mexico (Baja California Norte)

U. microscutatus

Small-Scaled Lizard, Small-Scaled Uta

USA (S California), Mexico (Baja California)

Max SVL 2”/5cm, avg SVL 1¾”/4cm

See notes on possible synonymisation with U. nigricaudus. Stebbins lists this species as U. nigricaudus. Smith cites this subspecies as basically a rock dweller in some areas, taking refuge in ground holes and supplanting Uta stansburiana, but more cosmopolitan in Baja California. Scalation: all dorsal and lateral scales very small, except slightly enlarged ones in narrow middorsal area; caudal scales very enlarged and heavily keeled, strongly mucronate; distinct granular gular fold; frontal entire. Other: 10-15 femoral pores; deep postfemoral pocket. Coloration: dorsally usually dark grey, sometimes lighter; back may be uniform or (more usually) 7-9 black transverse bands present either side of middorsal line, usually short but may extend on to sides; shoulder band most conspicuous with broken light posterior border; other bands may also have small light spots on posterior border; ventral surfaces white with numerous small black flecks in females, in males, grey and in large specimens darker, except for large blue belly patch either side which may merge in the middle; males have pale blue central gular region, the rest of the gular area being white or suffused with grey.

U. nigricaudus

Mexico (Baja California)

U. ornatus

Tree Lizard

USA (SE California, Utah, S Nevada, W Colorado, Arizona, New Mexico, SW & C Texas), Mexico (Baja California, Sonora, Sinaloa, Chihuahua, N Coahuila)

TL 4-5¼”/10-13½cm; max SVL 2”/5cm

The subspecies shown here are not listed by Stebbins, but are mostly included in the Reptile Database and described by Conant and Collins and Smith.

U. o. ornatus

Texas Tree Uta

USA (S & C Texas), Mexico (Coahuila)

Very arboreal lizard, also found on rail fences. Scalation: large posterior interparietal bordered eitehr side by parietal and frontoparietal; divided frontal; 4-5 enlarged supraoculars; 2 prefrontals, 3 frontonasals; single rostral separated by nasals by row of scales; nasals separated by pair of scales; elongate subocular; triangular mental bordered posteriorly by 2 scales between infralabials; ear opening bordered anteriorly by enlarged denticles. Dorsal scales very irregular in size; row of enlarged keeled scales on either side of middorsal line from just behind forelegs along tail, separated by 1-2 rows of small, keeled or smooth scales, and bordered laterally by another broken series of scales less than half the size of the innermost enlarged scales; lateral scales very small; distinct dorsolateral fold with clusters of enlarged scales becoming larger posteriorly but terminating anteriorly in pair of larger groups of scales; weak lateral fold; belly scales smooth, flat and imbricated. Other: usually 10-11 femoral pores; postfemoral pocket regularly present; males have enlarged postanals. Coloration: dorsally light grey to grey-brown; head lighter than body; indistinct transverse darker bands edged with blue on back; head patterned with numerous very fine brown lines; forelegs distinctly barred; belly light; chin and sides of throat mottled in adults; adult males have bright blue belly sides. Reproduction: 1-6 clutches of 2-16 eggs, laid March-August. [SOURCES: Smith, Stebbins].

U. o. caeruleus

Mexico (C Chihuahua)

SVL approx 5 cm

Scalation details: Two vertebral rows of enlarged, irregularly arranged, weakly carinated scales, extending from a point slightly craniad of a line joining the anterior points of insertion of the fore-limbs, posteriorly onto the base of the tail for a distance equal to the length of the femur; vertebrals bordered on either side by two series of enlarged, imbricate, weakly carinated scales, the primary series slightly larger than the secondary; largest of the dorsals inferior in size to the largest of the tibials; dorsolateral tubercles but slightly enlarged, and dispersed in irregular little clusters; ventrals rounded, smooth, imbricate; frontal transversely divided; a post-femoral dermal pocket. Coloration [of male (from original diagnosis)]: "Entire ventral surfaces of body and tail, except chest, base of tail, and an area between the hind legs, sky blue; dorsum with about seven transverse black bars on each side; bars usually blue-edged." [SOURCE: Mittelman]

U. o. chiricahuae

Chiricahuan Tree Uta

USA (Dos Cabezas Mountains, Cochise County, Arizona)

SVL approx 4.7 cm

Smith does not give much information on this subspecies, including habitat, and Stebbins does not mention it. Mittelman notes that it superficially resembles U. o. linearis but differs in having large enlarged dorsal scales, longer extension of the vertebral series of enlarged scales on to the basal portion of the tail, a proportionately wider head and a different arrangement of colours and patterns. Scalation: “much as in the northern cliff uta” [Smith]. Coloration: Smith describes this as being for the Lined Uta, except that the throat is normally uniform bluish and the preanal and chest regions more or less uniform grey. [SOURCE: Mittelman, Smith]

U. o. lateralis

U. o. levis

Smooth Tree Lizard, Swift Uta

USA (N/C New Mexico)

SVL approx 4.2 cm

Smith does not record much information on this subspecies, including habitat. Scalation: “much as in wrighti” [Smith] except that dorsal and lateral scales on tail base do not noticeably differ. Enlarged vertebrals and the three or four series of enlarged dorsals bordering them on either side, extremely flat, very weakly keeled, barely imbricate, or often pavemented; cervical, dorsolateral, and lateral tubercles absent or very poorly developed; lateral fold occasionally present, but then very weakly differentiated; dorsal scales of basal portion of tail very gradually merging to the lateral basal scales, without any noticeable demarcation between dorsal and lateral scales. Coloration: as for U. o. wrightii but lateral abdominal blue areas do not usually meet in the middle. [SOURCE: Mittelman, Smith]

U. o. linearis

Lined Uta

USA (S Arizona, S New Mexico), Mexico (N Sonora, Chihuahua)

Smith noted the “activity and alertness” of this species and its extreme ability to avoid capture. He also asserted the general rule that they associate in pairs. When excited the Lined Uta will very frequently perform “pressups” using all four limbs. This is another very arboreal subspecies. Scalation: large posterior interparietal bordered either side by parietal and frontoparietal; divided frontal; 4-5 enlarged supraoculars; 2 (sometimes 3) prefrontals, 5 frontonasals; single rostral separated by nasals by row of scales; nasals separated by pair of scales; elongate subocular; triangular mental bordered posteriorly by 2 scales between infralabials; ear opening bordered anteriorly by enlarged denticles. Dorsal scales very irregular in size; row of enlarged keeled scales on either side of middorsal line from just in front of forelegs along tail, separated by 1-2 (sometimes just 1, incomplete) rows of small, keeled or smooth scales, and bordered laterally by another broken series of scales nearly the sames size as that of the innermost enlarged scales; lateral tubercles may create impression of series of diagonal lines; weak lateral fold; belly scales smooth, flat and imbricated. Coloration: dorsally light to dark grey, sometimes with bluish tinge; 6-8 darker transverse bands, twice as wide as interspaces, usually broken in the middle and sometimes staggered, usually with white or blue edges especially posteriorly, and may be distinct or indistinct; dusky dark line from eye to rump may be present; limbs barred with similar colour, those on hind limbs usually dimmer; head usually intricately marked with fine lines; numerous dark transverse bands on tail, separated by much narrower light spaces; females have white ventral surfaces marked with black flecks and dots anteriorly and on the sides of the throat, and usually with elongate dark streaks on abdomen and sometimes chest, subcaudal area and underneath of hind legs, with a throat colour of uniform white, orange or yellow that in preservation fades to white or cream; males have pale blue belly sides from axilla to groin, these patches possibly meeting in the middle to create an entirely blue belly or else separated by a narrow central line, and a throat colour of pale greenish blue or yellow to orange, except on the lips and sides, which together with the underneath of the limbs are suffused with grey and usually streaked or mottled with black, this black mottling also occurring in the blue areas; male preanal region and underneath of hind limbs may be bluish. [SOURCE: Smith]

U. o. schmidti

Big Bend Tree Lizard, Big Bend Uta

USA (SW Texas), Mexico (N Chihuahua)

Found among rocks and boulders in desert habitat, where it is often associated with the Canyon Lizard Sceloporus merriami, but uses trees in mountainous areas [Conant and Collins]. Scalation: as for ornatus, but enlarged dorsal scales arranged more regularly, inner row of enlarged dorsal scales not twice as large as those of the outer row, and largest dorsal scales occasionally equal to but more often smaller than the enlarged keeled scales on the front of the limbs [Smith]. Coloration: “as for other races of ornatus, but ventral surfaces more nearly uniformly light, except for the blue areas on the sides of the belly in males” [Smith]. [SOURCES: Conant & Collins, Smith]

U. o. schotti

Schott's Tree Lizard

Mexico (Sonora, Sinoloa)

U. o. symmetricus

Colorado River Tree Lizard, Symmetrical Uta

USA (S California, Arizona), Mexico (W Sonora, N Baja California)

Smith describes this subspecies as being found almost exclusively on boulders and very seldom on the ground or trees. Scalation: usually 3 prefrontals and frontonasals (each); otherwise as in linearis but paravertebral rows of enlarged dorsals separated from each other by several rows of scales and width greater than that of largest dorsal scale. Coloration: similar to linearis, but lighter overall colour of light olive- to brownish-grey, with dim dark crossbands; supralabial region white or cream, continuing posteriorly to the ear and sometimes faintly beyond; ventrally uniform white; throat yellow to orange in females, blue or yellow to orange or combination of these in males; tail ventrally uniform white or slightly greyish; males have pale blue belly sides from near axilla to near groin. [SOURCE: Smith]

U. o. wrighti

Northern Cliff Uta

USA (S & E utah, SW California, N Arizona and NW New Mexico)

Not listed by the Reptile Database but recorded by Smith, who suggested on the basis of other authors that it was restricted to boulders, canyon walls and cliffs, and intergraded with U. o. linearis at the southern end of its rang. Scalation: most dorsal scales small and flat; several rows of enlarged keeled scales beginning just behind front edge of insertion of forelimbs and extendign to tail; middle 2 rows much smaller than the 2-3 rows on either side that grade either abruptly or gradually into granular lateral scales; scales on inner row of enlarged paravertebrals may be somewhat or much larger is size than those in the outer rows; few slightly enlarged dorsolateral scales form line posteriorly; no distinct enlarged tubercles on side of neck; lateral scales at base of tail abruptly smaller than dorsal basal scales. Other: 12-16 femoral pores; males have enlarged postanals. Coloration: overall pale grey to yellow-brown; 6-8 lighter dorsal crossbands, twice as wide as interspaces, frequently interrupted in the middle and sometimes staggered, sometimes flared at middle; limbs similarly barred, more noticeably on forelimbs; faint dark bands on tail, separated by narrow light interspaces and sometimes visible ventrally; dark narrow streak across top of head in middle of orbits usually present, with numerous other fine lines forming intricate pattern; ventrally white with faint mottling; in males sides of belly are dark blue, sometimes with faint lighter blue flecks, the dark blue often meeting in the middle; in males throat is blue, greenish blue, orange or yellow. [SOURCE: Smith]