Colorado Herpetological Society
Colorado's Lizards
by Lauren J. Livo
Evaluate the criteria below to identify a species.

1a. Spines on back of head, fringe of scales along side of body. go to 2
1b. Not as above. go to 4
2a. Long spines on back of head, dark bars radiating from eyes. Phrynosoma cornutum
Texas horned lizard
2b. Short spines on back of head, no dark bars radiating from eyes. go to 3
3a. Single row of fringe scales on sides of body. Phrynosoma hernandesi
Short-horned lizard
3b. No fringe scales on sides of body. Phrynosoma modestum
Roundtail horned lizard
4a. Scales on back pointed. go to 5
4b. Scales not as above. go to 7
5a. Black wedge-shaped mark on side of neck, up to 13 inches total length. Sceloporus magister
Desert spiny lizard
5b. No black mark on neck. go to 5
6a. Granular scales on rear of thigh, black bar usually present on shoulder. Sceloporus graciousus
Sagebrush lizard
6b. Keeled scales on rear of thigh, dorsal color variable. Sceloporus undulatus
Eastern fence lizard
7a. Scales very shiny and smooth. go to 8
7b. Scales variable, but not very shiny. go to 10
8a. Longitudinal stripes down length of very slender body; total length to about 7.75 inches. go to 9
8b. Individual scales clearly black and cream; total length to 13.75 inches. Eumeces obsoletus
Great Plains skink
9a. Light stripe along each side of back contrasting strongly with brown body and dark stripes; occurs south and west of Arkansas River. Eumeces gaigeae
Variable skink
9b. Body tan with several dark stripes; occurs north and east of Arkansas River. Eumeces multivirgatus
Many-lined skink
10a. No external ear openings. Holbrookia maculata
Lesser earless lizard
10b. External ear openings visible. go to 11
11a. Large and rectangular belly scales, neck not distinctly indented between head and body. go to 12
11b. Not as above. go to 16
12a. Checkered pattern. go to 13
12b. Stripes running length of body. go to 15
13a. Scales in front of gular fold abruptly enlarged; occurs on eastern slope. go to 14
13b. Scales in front of gular fold not abruptly enlarged; occurs on western slope. Cnemidophorus tigris
Western whiptail
14a. Posterior of thigh spotted or reticulated; double or single vertebral line from neck to base of tail, connected to paravetebral stripes in neck region by pale transverse bars. Cnemidophorus tesselatus
Diploid checkered whiptail
14b. Unbroken, irregular pale streak on posterior surface of one or both thighs; Vertebral line single and complete or present only on the neck and rump regions (if complete, usually no transverse bars in neck region connecting to paravertebral stripes). Cnemidophorus neotesselatus
Triploid checkered whiptail
15a. Occurs on eastern slope. Cnemidophorus sexlineatus
Six-lined racerunner
15b. Occurs on western slope. Cnemidophorus velox
Plateau striped whiptail
16a. Dark "collar" on neck. Crotaphytus collaris
Collared lizard
16b. Not as above. go to 17
17a. Conspicuous brown dots on back. Gambelia wislizenii
Longnose leopard lizard
17b. Not as above. go to 18
18a. Row of enlarged scales down middle of back. Urosaurus ornatus
Tree lizard
18b. Scales down middle of back not enlarged; black spot on chest behind foreleg. Uta stansburiana
Side-blotched lizard