Eteirodipsas, Lycodon[1] Trimorphodon is a genus of mildly venomous, rear-fanged, colubrid snakes.

Trimorphodon biscutatus ranges throughout the southwestern United States, from Texas to California as well as into northern Mexico.

Trimorphodon tau ranges through most of Mexico, and down into Central America, in Guatemala, El Salvador, Honduras, Nicaragua, and as far south as Costa Rica.

Trimorphodon species are primarily nocturnal, and feed on lizards, rodents and even bats.

They live inside rock crevices and canyon walls where humans cannot easily find them, which makes research difficult.