| 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 |