The plant-eating pelycosaur Cotylorhynchus probably was the largest of all non-mammal synapsids, at 20 feet (6.1 meters) and 2 tonnes.
Cotylorhynchus was a very large synapsid that lived in the southern part of what is now North America during the Early Permian period. It is the best known member of the synapsid clade Caseidae, the largest terrestrial vertebrates of the Early Permian. They were herbivores, and because of their enormous size, probably had no predators.
Cotylorhynchus was a heavily built animal with a disproportionately small head and a huge barrel-shaped body, adults of the species C. romeri were about 3 m (9.8 ft) while those of the younger C. hancocki were around 20-25% larger in linear measurements making it one of the largest synapsids of the early Permian.
Their skulls are distinctive in the presence of large temporal openings and very large nostril openings, which could have been utilized for better breathing or may have housed some sort of sensory or moisture conserving organ. Also they featured large pineal openings and a snout or upper jaw that overhangs the row of teeth to form a projecting rostrum. Rounded deep pits and possibly large depressions were present on the outer surface of the skull. Their teeth were very similar to those of iguanas with posterior marginal teeth that bore a longitudinal row of cusps.
Their skeletal features included a massive scapulocoracoid, humeri with large flared ends, stout forearm bones and broad, robust hands that had large claws. Certain features of their hands indicate that they had to dig considerably to obtain their food supply and also they may have used these features to dig burrows for shelter or safety. Their digits were believed to have a considerable range of motion and large retractor processes on the ventral surfaces of the unguals allowed them to flex their claws with powerful motions. Also, the articulatory surfaces of their phalanges were oblique to the bone's long axis rather than perpendicular to it. This allowed for much more surface area for the flexor muscles.
Cotylorhynchus were considered a part of the first wave of amniote diversity. There have been three species of Cotylorhynchus discovered: C. hancocki, C. romeri and C. bransoni. C. hancocki is believed to be a descendent of the slightly smaller C. romeri.
Various skeletal parts of C. romeri have been found around central Oklahoma in parts of Cleveland County.
Parts of C. hancocki have been found in northern Texas in Hardeman and Knox counties.
C. bransoni specimens have been uncovered in Kingfisher and Blaine Counties of central-northwest Oklahoma.
Moschops was the largest therapsid, with a weight of 700–1000 kg, and a length of about 5 meters. Moschops (Greek for "calf face") is an extinct genus of therapsid that lived in the Guadalupian epoch, around 265–260 million years ago. Therapsids are synapsids, which were at one time the dominant land animals. Its remains were found in the Karoo region of South Africa.
An artist's conception of Moschops capensis, based on the reconstruction of a skeleton found in a semi-desert region of South Africa. The skeleton is displayed at the American Museum of Natural History.
Moschops was a roughly 2.7-metre-long (9 ft), massively built dinocephalian. It had a short, thick and massive head, which was broad across the orbits. The occiput was broad and deep, but the skull was more narrow in the dorsal border. Furthermore, the pterygoid arches and the angular region of the jaw were quite heavy, allowing the insertion of strong jaw muscles. Due to that and because it possessed long-crowned, stout teeth, it is believed that Moschops was a herbivore feeding on nutrient-poor and tough vegetation, like cycad stems. Due to the presumably nutrient-poor food, it very likely had to feed for a very long time. Its anatomy allowed Moschops to open its elbow joint more widely, enabling it to move in a more mammal-like way than the other crawlers in its time. That might have helped it to carry its massive body more easily while feeding.Very likely, most dinocephalians were rather slow-moving animals, but capable of raising themselves, for short bursts. It is also possible that Moschops and other dinocephalians were semiaquatic, given the heavy build and the limbs with their spreading hands and feet. The heavy head could have been useful for diving after food.
Moschops had a thick skull, prompting speculation that individuals competed with one another by head-butting.Some doubt whether the Moschops were born with thick skulls. If they were, then Moschops' short, heavy tail may have counterbalanced the weight of its head. Its main enemies were very likely titanosuchids and the larger therocephalians.
Moschops material was discovered for the first time by Robert Broom in the Ecca Group (part of the Karoo Supergroup) in South Africa. The geological horizon dubious, it was referred to that group on the basis of Pareiasaurus remains in the near. The material includes a holotype (AMNH 5550) and seven topotypes (AMNH 5551-5557). The degree of pachyostosis varies within the skulls of the specimens. According to Broom, it is because of gender and age variation within the discovered specimens. In 1910, the material was sent to the American Museum of Natural History in New York and it was described in 1911.
Moschops is characterized by a strongly pachyostosed skull with a broad intertemporal region and greatly reduced temporal fossae. Two species are known from good fossil record, M. capensis and M. koupensis. Two other species were assigned (M. whaitsi and M. oweni), but the validity is doubtful.
Genera regarded as synonyms are Moschoides, Agnosaurus, Moschognathus and Pnigalion.
Another taxon, Delphinognathus conocephalus, could have been a synonym also, as it could represent a juvenile Moschops. This taxon is known from a single, moderately pachyostosed skull. It has a conical boss on the parietal surrounding the pineal foramen.
The largest is Scutosaurus, up to 3 metres (9.8 ft) in length, with bony armor, and a number of spikes decorating its skull
Scutosaurus was a massively built reptile, up to 3 metres (9.8 ft) in length, with bony armor, and a number of spikes decorating its skull.Despite its relatively small size, Scutosaurus was heavy, and its short legs meant that it could not move at speed for long periods of time, which made it vulnerable to attack by large predators. To defend itself Scutosaurus had a thick skeleton covered with powerful muscles, especially in the neck region. Underneath the skin were rows of hard, bony plates (scutes) that acted like a form of chain mail.
As a plant-eater living in a semi-arid climate, Scutosaurus would have wandered widely in order to find fresh foliage to eat. It may have stuck closely to the riverbanks and floodplains where plant life would have been more abundant, straying further afield only during times of drought. Its teeth were flattened and could grind away at the leaves and young branches before digesting them at length in its large gut. Given that it needed to eat constantly, Scutosaurus probably lived alone, or in very small herds, so as to avoid denuding large areas of their edible plants.
The skull is about 50 cm wide.It is very broad, flat, and strongly sculptured, and bears bony protuberances in the jugal (cheek) and rear regions. As with some species of Pareiasaurus, with which it is clearly related, the quadrato-jugal or cheekbones extend outwards and forwards, makings an angle of about 120° with the maxillary border.With its large cheekbones, Scutosaurus may have been able to make a loud bellowing sound
Although related to Titanosuchus, Jonkeria appears to be at the other end of the spectrum by being envisioned as an herbivore. However the similarity to Titanosuchus has led some to suggest that Jonkeria may actually be a carnivore, with the most obvious difference between the two being Jonkeria having shorter legs.
Aside from having a similar morphology to Titanosuchus, the main anti herbivore argument for Jonkeria comes from the presence of large incisor and canine teeth. Aside from indicating a lineage to carnivorous ancestors, these teeth were capable of making short work of flesh. One possibility is that Jonkeria was actually omnivorous and used its size to not only kill large herbivores but to dominate the smaller carnivores, stealing their kills. Such behaviour can be seen in modern day bears which are opportunistic omnivores, killing their own prey, stealing the prey of other carnivores like wolves, and eating suitable plants when able. If the analogy is true, then Jonkeria would have been feared by everything.
Jonkeria once had a large number of species attributed to it, but re-examination of the remains has found that many of these species were already described under different Jonkeria species names. Many of the species listed above may yet also prove synonymous with the type species J. truculenta among others.