Toothy worm-like creatures called caecilians have smooth, shiny skin and already look a lot like snakes. Still, scientists were surprised to discover some of these legless animals may have venomous saliva—possibly the first example ever found in amphibians.

Nearly 200 caecilian species wiggle through tropical forests the world over, ranging from the 3.5-inch-long Idiocranium russell in Cameroon to the nearly five-foot-long giant known as Caecilia thompsoni in Colombia.

Most of the animals dwell underground, which is why “caecilians are maybe the most unknown group of vertebrates,” says Carlos Jared, an evolutionary biologist at the Butantan Institute in São Paulo, Brazil, and author of a new study on the animals. Some species are so adapted to subterranean life,