Eryops (; from Greek , , 'drawn-out' + , , 'face', because most of its skull was in front of its eyes) is a genus of extinct, amphibious temnospondyls. It contains the single species , the fossils of which are found mainly in early Permian (about 295 million years ago) rocks of the Texas Red Beds, located in Archer County, Texas. Fossils have also been found in late Carboniferous period rocks from New Mexico. Several complete skeletons of Eryops have been found in lower Permian rocks, but skull bones and teeth are its most common fossils.
Description
Eryops averaged a little over long and could grow up to , making them among the largest land animals of their time. Adults weighed between . The skull was proportionately large, being broad and flat and reaching lengths of . It had an enormous mouth with many curved teeth, like those of frogs. Its teeth had enamel with a folded pattern, leading to its early classification as a "labyrinthodont" ("maze toothed"). The shape and cross section of Eryops teeth made them exceptionally strong and resistant to stresses. The palate, or roof of the mouth, contained three pairs of backward-curved fangs, and was covered in backward-pointing bony projections which would have been used to trap slippery prey once caught. This, coupled with the wide gape, suggest an inertial method of feeding, in which the animal would grasp its prey and thrust forward, forcing the prey farther back into its mouth.<ref name= Rinehart&lucas2013>{ { cite journal|last1=Rinehart, L. F. |last2=Lucas, S. G. |year=2013 |title=Tooth form and function in temnospondyl amphibians: relationship of shape to applied stress |journal=New Mexico Museum of Natural History Bulletin |volume=61' |pages=533–542 |url=http://paleo.cortland.edu/globaltriassic2/Bulletin%2061%20Final/40-Rinehart%20and%20Lucas%20(Metopo%20teeth).pdf}}</ref>Eryops was much more strongly built and sturdy than its relatives, and had the most massive and heavily ossified skeleton of all known temnospondyls. The limbs were especially large and strong. The pectoral girdle was highly developed, with a larger size for increased muscle attachments. Most notably, the shoulder girdle was disconnected from the skull, resulting in improved terrestrial locomotion. The crossopterygian cleithrum was retained as the clavicle, and the interclavicle was well-developed, lying on the underside of the chest. In primitive forms, the two clavicles and the interclavicle could have grown ventrally in such a way as to form a broad chest plate, although such was not the case in Eryops. The upper portion of the girdle had a flat scapular blade, with the glenoid cavity situated below performing as the articulation surface for the humerus, while ventrally there was a large flat coracoid plate turning in toward the midline.
The pelvic girdle also was much larger than the simple plate found in fishes, accommodating more muscles. It extended far dorsally and was joined to the backbone by one or more specialized sacral ribs. The hind legs were somewhat specialized in that they not only supported weight, but also provided propulsion. The dorsal extension of the pelvis was the ilium, while the broad ventral plate was composed of the pubis in front and the ischium behind. The three bones met at a single point in the center of the pelvic triangle, called the acetabulum, providing a surface of articulation for the femur.
The texture of Eryops skin was revealed by a fossilized "mummy" described in 1941. This mummy specimen showed that the body in life was covered in a pattern of oval bumps.