Eryops is currently thought to contain two presently valid species. The type species,
E. megacephalus, refers to the "large-headed" aspect of the genus. Remains of
E. megacephalus have been found in rocks dated to the early
Permian period (
Sakmarian age, about 295 million years ago) in the southwestern United States. Most of these specimens, including the type material, have little to no locality information other than that they are from the early Permian of Texas, but more definitively placed specimens are recorded for much of the Cisuralian, including the Putnam, Admiral, Belle Plains, and Clyde Formations. Various other valid temnospondyl taxa were previously placed in the genus. During the mid-20th century, some older fossils were classified as a second species of
Eryops,
E. avinoffi. This species, known from
Carboniferous period fossil found in
Pennsylvania, had originally been classified in the genus
Glaukerpeton. Beginning in the late 1950s, '
Eryops anatinus and Eryops latus' are both junior synonyms of
E. megacephalus.
Eryops ferricolus is now recognized as a
dissorophid,
Parioxys,
Eryops platypus is a junior synonym of the
amphibamid Platyrhinops lyelli, and
Eryops africanus and
Eryops oweni are
rhinesuchids.
Eryops reticulatus is regarded as a
nomen vanum, New Mexico, Oklahoma, and Prince Edward Island. The primary material of
Eryops that has been reported from the
Conemaugh Group in West Virginia has also been reidentified as
Glaukerpeton, although unpublished specimens referred to
Eryops sp. (and with acknowledgment of the validity of
Glaukerpeton) have been listed from this region. ==Paleobiology==