Eryops megacephalus (pron.: /ˈɛəri.ɒps/) meaning "drawn-out face" because most of its skull was in front of its eyes (Greek ἐρύειν, eryein = drawn-out + ὤψ, ops = face) is a genus of extinct, semi-aquatic temnospondyl amphibian found primarily in the Lower Permian-aged Admiral Formation (about 295 mya) of Archer County, Texas, but fossils are also found in New Mexico and parts of the eastern United States. Eryops also occurs in older Pennsylvanian strata of the Conemaugh Group in West Virginia Eryops averaged a little over 1.5-2.0 meters (5–6 feet) long, making it one of the largest land animals of its time. It weighed about 90 kilograms (200 lbs). It probably had few predators, although it would have likely been preyed upon by Dimetrodon, which was larger and was the apex predator at the time. Several complete skeletons of Eryops have been found in the Lower Permian deposits, but skull bones and teeth are the most common fossils. Although it had no direct descendants, it is the best-known Permian amphibian and a remarkable example of natural engineering.
Eryops is an example of an animal that made successful adaptations in the movement from a water environment to a terrestrial one. It retained, and refined, most of the traits found in its marine ancestors. Sturdy limbs supported and transported its body while out of water. A thicker, stronger backbone prevented its body from sagging under its own weight. Also, by utilizing vestigial fish jaw bones, a rudimentary ear was developed, allowing Eryops to hear airborne sound.
Description[]
Eryops megacephalus
The skull of Eryops is proportionately large, being broad and flat and reaching lengths of 60 centimeters (2 ft). It had an enormous mouth with many sharp teeth in strong jaws. Its teeth had enamel with a folded pattern, hence its classification with the labyrinthodonts ("maze toothed"). Within the wide, gaping jaw, the fang-like palatal teeth, when coupled with the gape, suggest an inertial feeding habit. This is when the amphibian would grasp its prey and, lacking any chewing mechanism, toss its head up and backwards, throwing the prey farther back into its mouth. Such feeding is seen today in the crocodile and alligator. It is taken that Eryops was not very active, thus a predatory lifestyle, while possible, was probably not the norm. It is more likely that it fed on fish either in the water or on those that became stranded at the margins of lakes and swamps. A large supply of terrestrial invertebrates were also abundant at the time, and this may have provided a fairly adequate food supply in itself.
Front view of Eryops megacephalus
Eryops’ eye sockets were large and directed upward. The body was low to the ground and supported by short, massive limbs. The tail was short, suggesting the animal was not a fast or powerful swimmer. The flat skull with the large eyes and nostrils placed on the top of the head are suggestive that Eryops used stealth for hunting, much like a modern crocodile, and sat quietly in the water waiting for prey with only its eyes and nostrils visible above the water.
The pectoral girdle of Eryops was highly developed, with a larger size for both increased muscle attachment to both it and the limbs. 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 comprised 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.
Dimetrodon gigas & Eryops megacephalus
The main strength of the ilio-sacral attachment of Eryops was by ligaments, a condition structurally, but not phylogenetically, intermediate between that of the most primitive embolomerous amphibians and early reptiles. The condition that is more usually found in later vertebrates is that cartilage and fusion of the sacral ribs to the blade of the ilium are utilized in addition to ligamentous attachments.
Locomotion[]
life restoration of Eryops megacephalus
Eryops had typical amphibian posture exhibited by the upper arm and upper leg extending nearly straight out from its body, while the forearm and the lower leg extended downward from the upper segment at a near right angle. The body weight was not centered over the limbs, but was rather transferred 90 degrees outward and down through the lower limbs, which contacted the ground. Most of the animal's strength was used to just elevate its body off the ground for walking, which was probably slow and difficult. With this sort of posture, only short, broad strides could be achieved. This has been confirmed by fossilized footprints found in Carboniferous rocks.
Ligamentous attachments within the limbs were present in Eryops, being important because they were the precursor to bony and cartilagenous variations seen in modern terrestrial animals that use their limbs for locomotion.
The primary species of Eryops has been named Eryops megacephalus (“big head”).
Discovery and species[]
_at_G%C3%B6teborgs_Naturhistoriska_Museum_2355.jpg){kind=link}
Cast of the skull
Eryops is currently thought to contain only one species, E. megacephalus, which means "large-headed Eryops". E. megacephalus fossils have been found only in rocks dated to the early Permian period (Sakmarian age, about 295 million years ago) in the southwestern United States, primarily in the Admiral Formation of the Texas Red Beds. 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, some scientists concluded that Glaukerpeton was too similar to Eyrops to deserve its own genus. However, later studies supported the original classification of Glaukerpeton, finding that it was more primitive than Eryops and some other early temnospondyls. Supposed Eryops fossils also found in older Pennsylvanian epoch rocks of the Conemaugh Group in West Virginia also turned out to be remains of Glaukerpeton. In 2005, a skull clearly belonging to Eryops was found in upper Pennsylvanian epoch rocks of the El Cobre Canyon Formation in New Mexico, representing the oldest known specimen.
Paleobiology[]
Eryops were among the most formidable early Permian carnivores and perhaps the only ones capable of competing with the dominant synapsids of the time, though because they were semi-aquatic, if not mostly aquatic, as suggested by long bone microanatomy, they probably did not come into frequent competition with synapsids. Eryops lived in lowland habitats in and around ponds, streams, and rivers, and the arrangement and shape of their teeth suggests that they probably ate mostly large fish and aquatic tetrapods. The torso of Eryops was relatively stiff and the tail stout, which would have made them poor swimmers. While they probably fed on fish, adult Eryops must have spent most of their time on land.
Like other large primitive temnospondyls, Eryops would have grown slowly and gradually from aquatic larvae, but they did not go through a major metamorphosis like many modern amphibians. While adults probably lived in ponds and rivers, perhaps venturing onto their banks, juvenile Eryops may have lived in swamps, which possibly offered more shelter from predators.
Appearance in other media[]
Jurassic Park Franchise[]
- Eryops features in Jurassic World: The Game as a tournament creature.
 |
Read more Eryops on Jurassic Park Wiki |