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A Guide to the Amphibians
and Reptiles of California

Trimorphodon biscutatus lambda - Sonoran Lyresnake

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Range in California: Green

Red: Baja California Lyresnake

observation link

  Adult, Santa Cruz County, Arizona  
  Adult, Arizona, © Chris Gruenwald
  Possible habitat, Chemehuevi Mountains, San Bernardino County  

Mildly Venomous
One of the larger rear-fanged snakes, but considered harmless to humans, but handle with caution, as some people have had unpleasant reactions to this snake's bite.
Trimorphodon biscutatus have been recorded from 18 - 47 3/4 inches in length (46 - 121 cm). Most snakes encountered are 24 - 36 inches long (61 - 91 cm).
A slender snake with a broad head well-differentiated from the slim neck. Coloring closely matches a snake's rocky habitat, from gray to light brown. There are usually about 28 large dorsal blotches with light edges and a pale crossbar in the center, and smaller irregular blotches on the lower sides. A lyre-shaped marking is present on top of the head. The pupils are vertical, like those of a cat. The underside is off-white or yellowish with dark spots. The anal plate is usually divided.
Nocturnal, active in very dry conditions as well as during rains. Terrestrial, and good climbers. This snake often searches rock crevices for prey. It can be found during the day inside crevices in large rock outcrops, as well as crossing desert roads at night.
Primarily lizards, but also known to eat small mammals, nestling birds, and snakes.
Not well known. Lyre snakes apparently originated in the tropics, where breeding is year round, and the northern races may have retained this capability.
In California, found only in the southeast along the Colorado River from approximately the Riverside/Imperial County line, north into San Bernardino County and the Nevada border. Ranges north into southern Nevada and extreme southwest Utah, through Arizona and extreme southwest New Mexico, south into Sonora and Sinaloa, Mexico.
Associated primarily with rocky desert locations, but found in rockless areas, also.
Taxonomic Notes
Some researchers do not recognize any subspecies of Trimorphodon biscutatus.

Devitt et al, in a 2008 paper, recommended that this snake be recognized as a distinct species, Trimorphodon lambda - Sonoran Lyre Snake.

The former subspecies T. b. vandenburghi was synonymized with T. b. lyrophanes in 1994 (Grismer et al. (1994 Bull. So,. California Acad. Sci. 93: 45-80).
Conservation Issues  (Conservation Status)

Family Colubridae Colubrids
Genus Trimorphodon Lyresnakes
Species biscutatus Lyresnake

lambda Sonoran Lyresnake
Original Description
Trimorphodon biscutatus - (Dumeril, Bibron and Dumeril, 1854) - Erpet. Gen., Vol. 7, Pt. 2, p. 1153
Trimorphodon biscutatus lambda - Cope, 1886 - Proc. Amer. Philos. Soc., Vol. 23, p. 286

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

Meaning of the Scientific Name
Trimorphodon - Greek - tri - three, and morph - shape, and odon- teeth - refers to the 3 tooth shapes in the upper jaw,                            recurved anterior teeth;  the shorter middle teeth, and elongate grooved fangs at the rear.
- Latin - bis - two, and scutatus- plated - refers to the doubled loreal plate
lambda - Greek - letter of Greek alphabet - refers to the chevron-shaped mark on head

from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

Alternate Names
Trimorphodon biscutatus - Western Lyre Snake (no subspecies recognized)

Related or Similar California Snakes
T. b. lyrophanes - Baja California Lyresnake
Sonoran Gopher Snake
Desert Glossy Snake

More Information and References
Natureserve Explorer

California Dept. of Fish and Game

Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.

Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.

Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.

Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Snakes of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.

Bartlett, R.D. , & Alan Tennant. Snakes of North America - Western Region. Gulf Publishing Co., 2000.

Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997.

Ernst, Carl H., Evelyn M. Ernst, & Robert M. Corker. Snakes of the United States and Canada. Smithsonian Institution Press, 2003.

Wright, Albert Hazen & Anna Allen Wright. Handbook of Snakes of the United States and Canada. Cornell University Press.

Devitt, Thomas J., Travis J. LaDuc, and Jimmy A. McGuire. The Trimorphodon biscutatus (Squamata: Colubridae) Species Complex Revisited: A Multivariate Statistical Analysis of Geographic Variation. Copeia. 2008 (2): 370-387.

Conservation Status

The following status listings come from the Special Animals List which is published several times each year by the California Department of Fish and Game.

This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
Status Listing
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Game None
Bureau of Land Management None
USDA Forest Service None
Natureserve Global Conservation Status Ranks
World Conservation Union - IUCN Red List


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