Xibalbanus tulumensis

Remipedes are blind, cave-dwelling crustaceans of flooded caves along the coasts of Mexico and Central America, places reached only by cave divers. This species, from the Yucatán, gave the group its claim to fame: a 2013 study showed it was the first crustacean known to use venom to capture and kill prey. A pair of glands in the front of its body makes the venom, and one of its toxins closely resembles a type of neurotoxin first described in spider venom. In water where prey is scarce and hard to find, disabling whatever it catches is a sound strategy.