Onychonycteris known species, hence "Onychonycteris" meaning "clawed bat". The specific epithet is a tribute to the fossil prospector and preparator who discovered it, Bonnie Finney. "Onychonycteris finneyi" was the strongest evidence so far in the debate on whether bats developed echolocation before or after they evolved the ability to fly. "O. finneyi" had well-developed wings, and could clearly fly, but lacked the enlarged cochlea of all extant echolocating bats, closer resembling the old world fruit bats which do not echolocate. This indicates that early bats could fly before they could echolocate. However, an independent evaluation of the "Onychonycteris" reference fossil in
Mexican free-tailed bat bats. Their ears are wide, rounded, and large compared to their head, nearly meeting at the front of the face but distinctly not joined at the midline and projecting anterodorsally from just before the muzzle to the back of the head. They use their large ears to help them find prey using echolocation. "T. brasiliensis" is distinguished among North American Tadarida bats in possessing deep wrinkles on the upper lip and in having a Z-shaped upper third molar which is used for grinding insects. These individuals possess canines which are larger in males than in females. The wings are elongated