U.S. biologists have discovered a new and distinct species of crayfish in Tennessee and Alabama that is twice the size of other species, an example of a new species being discovered in a well-explored area.

Researchers from the University of Illinois at Urbana-Champaign and Eastern Kentucky University found the first specimen under a large rock in the deep waters of a Tennessee creek after hearing reports of similar findings. The new species of crustacean, called Barbicambarus simmonsi, is about five inches long and has an unusual “bearded” antennae as a result of the presence of tiny hair-like bristles called setae.