Five-toed Worm Lizard

B. biporus is pink and worm-like, 18–24 cm (7.1–9.4 in) in snout-to-vent length (SVL) and 6–7 mm (0.24–0.28 in) in width. It lives for one to two years. Its skin is closely segmented to give a corrugated appearance, and like earthworms, its underground movement is by peristalsis of the segments. Its blunt head allows it to burrow into sandy soils efficiently. The forelegs are short, strong and paddle-like, while the hind legs are absent, only having vestigial bones. The tail is autotomous without any regeneration. Due to sacrificing the development of its ear to permit it to dig more efficiently, the Mexican mole lizard has evolved to have its skin transmit vibrations to the cochlea.

The Mexican mole lizard (B. biporus) is found in the states of Baja California, Baja California Sur, Guerrero and Chiapas, in Mexico. These species tend to be found on this peninsula near the sandy soils in desert with dry shrub land. They spend their time burrowed from 2.5 cm to 15 cm.

B. biporus is oviparous, and the females lay one to four eggs in midsummer. The species only breeds underground. The eggs hatch after two months. The juveniles tend to be pink and then turn white as they grow. B. biporus does not exhibit sexual dimorphism, with their gender only being determined by looking at their gonads.