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Biodiversity Blog


Texas Alligator Lizard


Tx infernalis cropped 
 Photo: Dr. Eric Pianka


The Texas Alligator Lizard (Gerrhonotus infernalis) is the largest lizard with limbs in Texas, exceeded in length only by Slender Glass Lizards, which are legless. It is also one of the largest alligator lizards in the world. Adults are about 16”-18” in length and endemic to the central region of Texas, and into northern Mexico.

The Texas Alligator Lizard is diurnal, and feeds primarily on spiders, insects, and small vertebrates. Sometimes, it does eat rodents or nestling birds.

This lizard is not generally aggressive, but can bite if handled. It is not venomous. Its tail can fall off to distract a predator, but will regrow.

This type of Gerrhonotus infernalis was collected by army surgeon Caleb Kennerly in 1854, at what is now called Baker’s Crossing on the Devil’s River, Val Verde Co, Texas. Kennerly wrote Naturalist Spencer Fullerton Baird of finding the “large lizzard [sic] in bushes,” and Baird elsewhere described Kennerly as “the most notorious snake, salamander, bug, cave-bone, wolf, panther, and tadpole catcher in the community, your humble servant perhaps excepted.”

Baird described the species in 1859, and used the specific name “infernalis” because he found the specimen along the Devil's river. “Infernalis” is Latin for “underground” or “belonging to the lower regions.” The lizard does actually have semi fossorial habits, meaning, it lives primarily but not entirely underground. They are also arboreal.

Although many reptiles don’t provide parental care for their clutch after laying eggs, Texas Alligator lizards certainly do. The female remains with her clutch of eggs, hidden under a rock or in a rocky outcrop, for the couple of months it takes them to incubate. In captivity, the female lizard has been seen to become defensive of her egg clutch, and leave the nest only to eat or defecate.


Threat display. (Video: Dr. Eric Pianka.)

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