Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typically toothless beak, unique amongst all synapsids. Dicynodonts first appeared in Southern Pangaea during the mid-Permian, ca. 270–260 million years ago, and became globally distributed and the dominant herbivorous animals in the Late Permian, ca. 260–252 Mya. They were devastated by the end-Permian Extinction that wiped out most other therapsids ca. 252 Mya. They rebounded during the Triassic but died out towards the end of that period. They were the most successful and diverse of the non-mammalian therapsids, with over 70 genera known, varying from rat-sized burrowers to elephant-sized browsers.
Kannemeyeria is a genus of dicynodont that lived during the Anisian age of Middle Triassic period in what is now Africa and South America. The generic name is given in honor of Daniel Rossouw Kannemeyer, the South African fossil collector who discovered the original specimen. It is one of the first representatives of the family, and hence one of the first large herbivores of the Triassic.
Emydops is an extinct genus of dicynodont therapsids from the Middle Permian to Late Permian of what is now South Africa. The genus is generally small and herbivorous, sharing the dicynodont synapomorphy of bearing two tusks. In the following years, the genus grew to include fourteen species. Many of these species were erected on the basis of differences in the teeth and the positioning of the frontal and parietal bones. A 2008 study narrowed Emydops down to two species, E. arctatus and the newly described E. oweni.
Stahleckeriidae is a family of dicynodont therapsids whose fossils are known from the Triassic of North America, South America, Asia and Africa.
Wadiasaurus is an extinct genus of dicynodont from the family Kannemeyeria, that lived in herds from the early to Middle Triassic. Substantial fossorial evidence of W. indicus was recovered from Yerrapalli Formation of the Pranhita-Godavari valley, India, and it is so far the only Kannemeyeriid known for certain from India. The Kannemeyeriiformes underwent a significant diversification during the middle Triassic, with roughly 40 known species distributed worldwide. All Kannemeyeriiformes were medium to large bodied, graviportal herbivores with relatively erect posture and gait. Wadiasaurus indicus is currently the only known species of Wadiasaurus.
Myosaurus is a genus of Anomodontia in the order Therapsida. They are also classified as Dicynodontia, which is a subclade of Anomodontia. The Mysosaurus was a small, herbivorous synapsid that existed around the early Triassic period. All of the fossils found of this species were found in Antarctica and South Africa. Compared to other fossils found from species that existed during this time, the Myosaurus is not common in the fossil record. This is due to a shortage of discovered fossils that possess characteristics unique to the Myosaurus. Notably, under 130 fossil fragments have been found that have been classified as Myosauridae, and almost all have been skulls. These skulls can be classified as Myosaurus because this species, unlike other dicynodonts, do not possess tusks or postfrontal teeth. The only species identified in the family Myosauridae is the Myosaurus gracilis, or M. gracilis. It should be recognized that the Myosaurus is almost always referred to as the M. gracilis in scientific research.
Angonisaurus is an extinct genus of kannemeyeriiform dicynodont from the Middle Triassic of Africa between 247 and 242 million years ago. Only one species, Angonisaurus cruickshanki has been assigned to this genus. This genus is thought to have been widely spread but rare in southern Gondwana. Though few in number, the fossil record of Angonisaurus cruickshanki contains multiple specimens giving it a measurable stratigraphic range. Sexually dimorphic features are found in Angonisaurus which include presence or absence of tusks and difference is size and robustness of the temporal arch and the rostral.
Biseridens is an extinct genus of anomodont therapsid, and one of the most basal anomodont genera known. Originally known from a partial skull misidentified as an eotitanosuchian in 1997, another well-preserved skull was found in the Qingtoushan Formation in the Qilian Mountains of Gansu, China, in 2009 that clarified its relationships to anomodonts, such as the dicynodonts.
Dicynodontoides is a genus of small to medium-bodied, herbivorous, emydopoid dicynodonts from the Late Permian. The name Dicynodontoides references its “dicynodont-like” appearance due to the caniniform tusks featured by most members of this infraorder. Kingoria, a junior synonym, has been used more widely in the literature than the more obscure Dicynodontoides, which is similar-sounding to another distantly related genus of dicynodont, Dicynodon. Two species are recognized: D. recurvidens from South Africa, and D. nowacki from Tanzania.
Sangusaurus is an extinct genus of large dicynodont synapsid with two recognized species: S. edentatus and S. parringtonii. Sangusaurus is named after the Sangu stream in eastern Zambia near to where it was first discovered + ‘saur’ which is the Greek root for lizard. Sangusaurus fossils have been recovered from the upper parts of the Ntawere Formation in Zambia and of the Lifua Member of the Manda Beds in Tanzania. The earliest study considered Sangusaurus a kannemeyeriid dicynodont, but more recent phylogenetic analyses place Sangusaurus within the stahleckeriid clade of Dicynodontia. Until recently, little work had been done to describe Sangusaurus, likely due to the fact that only four incomplete fossil specimens have been discovered.
Lystrosauridae is a family of dicynodont therapsids from the Permian and Triassic time periods. It includes two genera, Lystrosaurus and Kwazulusaurus. Kwazulusaurus includes a single species, K. shakai, from the Late Permian of South Africa and Lystrosaurus includes many species from the Late Permian and Early Triassic of South Africa, India, and Antarctica.
Shaanbeikannemeyeria is an extinct genus of dicynodont known from the Early Triassic of China. It contains a single species, S. xilougoensis, which was described in 1980 by Zheng-Wu Cheng from a skull catalogued as IGCAGS V315. The specimen was lost, and a neotype skull IVPP V 11674 was later designated. A second species, S. buergondia, was named by Jin-Lin Li in 1980 from a partial skeleton, but it has since been regarded as a synonym of S. xilougoensis.
Kannemeyeriiformes is a group of large-bodied Triassic dicynodonts. As a clade, Kannemeyeriiformes has been defined to include the species Kannemeyeria simocephalus and all dicynodonts more closely related to it than to the species Lystrosaurus murrayi.
The Ermaying Formation is a geological formation of Anisian age in north-central China. It is found across much of the Ordos Basin, at outcrops within the provinces of Shaanxi, Shanxi, and Inner Mongolia. It is composed of up to 600 m thick sequence of mudstone and sandstone, overlying the Heshanggou Formation and underlying the Tongchuan Formation. In the southern part of the Ordos Basin, the Zhifang Formation is equivalent to the Ermaying Formation.
Pentasaurus is an extinct genus of dicynodont of the family Stahleckeriidae, closely related to the well known Placerias. It was found in the Lower Elliot Formation of South Africa, dated to the Norian of the Late Triassic period. The genus contains the type and only species, Pentasaurus goggai. Pentasaurus is named after the ichnogenus Pentasauropus, fossil footprints that were originally described from the lower Elliot Formation in 1970 decades before the body fossils of Pentasaurus itself were recognised. Pentasauropus footprints were likely made by dicynodonts, and in South Africa Pentasaurus itself was the likely trackmaker. The name reflects the fact that a large dicynodont was predicted to have existed in the lower Elliot Formation before any body fossils were recognised, and so Pentasaurus was named after its probable footprints. This is a reversal of the more typical occurrence where fossil footprints are named after their presumed trackmakers. The name of the species honours its collector Alfred Brown, nicknamed "Gogga", which means "bug" in Afrikaans.
Lisowicia is an extinct genus of giant dicynodont synapsid that lived in what is now Poland during the late Norian or earliest Rhaetian age of the Late Triassic Period, about 210–205 million years ago. Lisowicia is the largest known dicynodont, as well as the largest non-mammalian synapsid, reaching about 4.5 metres (15 ft) long, standing up to 2.6 metres (8.5 ft) tall at the hips and weighing around 5–7 metric tons, comparable in size to modern elephants. It was also one of the last dicynodonts, living shortly before their extinction at the end of the Triassic period. Fossils of a giant dicynodont were known from Poland since 2008, but Lisowicia was not named and officially described as a new species until late 2018.
Thliptosaurus is an extinct genus of small kingoriid dicynodont from the latest Permian period of the Karoo Basin in KwaZulu-Natal, South Africa. It contains the type and only known species T. imperforatus. Thliptosaurus is from the upper Daptocephalus Assemblage Zone, making it one of the youngest Permian dicynodonts known, living just prior to the Permian mass extinction. It also represents one of the few small bodied dicynodonts to exist at this time, when most other dicynodonts had large body sizes and many small dicynodonts had gone extinct. The unexpected discovery of Thliptosaurus in a region of the Karoo outside of the historically sampled localities suggests that it may have been part of an endemic local fauna not found in these historic sites. Such under-sampled localities may contain 'hidden diversities' of Permian faunas that are unknown from traditional samples. Thliptosaurus is also unusual for dicynodonts as it lacks a pineal foramen, suggesting that it played a much less important role in thermoregulation than it did for other dicynodonts.
Repelinosaurus is an extinct genus of dicynodont from the Purple Claystone Formation of Luang Prabang in Laos, Southeast Asia that lived at around the time of the Permian-Triassic boundary and possibly dates to the earliest Early Triassic. Its type and only known species is R. robustus. Repelinosaurus was originally described as the earliest known kannemeyeriiform dicynodont, supporting the idea of a more rapid radiation of the Triassic kannemeyeriiform dicynodonts during the Early Triassic following the Permian mass extinction. However, it may alternatively be more closely related to the Permian Dicynodon. The discovery of a potential early kannemeyeriiform in an understudied locality like Laos highlights the importance of such places in dicynodont research, which has been largely focused on historically important localities such as the Karoo Basin of South Africa.
Ufudocyclops is an extinct genus of stahleckeriid dicynodont from the Middle Triassic of South Africa. It was found in the Burgersdorp Formation, part of the uppermost Cynognathus Assemblage Zone of the Beaufort Group in the Karoo Basin. The type and only known species is U. mukanelai. It was a large, beaked herbivore like other Triassic dicynodonts, lacking tusks, and is mostly characterised by unique features of the skull. It is known from three specimens, two of which were previously referred to the Tanzanian dicynodont Angonisaurus. The separation of Ufudocyclops from Angonisaurus indicates that the Middle Triassic fauna of the Beaufort Group in South Africa was not part of a larger shared fauna with those of the Manda Beds in Tanzania, as was previously supposed, and suggests that they were separated as more localised faunas, possibly by geographic barriers or in time. Ufudocyclops then would have been a unique part of the uppermost Cynognathus Assemblage Zone in South Africa. It is also the oldest known member of the family Stahleckeriidae, and implies that the family was already diversifying in the Middle Triassic alongside other kannemeyeriiforms, not just in the Late Triassic after other families died out.
Taoheodon is an extinct genus of dicynodont therapsid from the Sunjiagou Formation in the Shanxi province of China, dated to the Wuchiapingian age of the Late Permian. Its type and only known species is T. baizhijuni. Taoheodon was a close relative of the well known Dicynodon, and may represent a biogeographical link between the South African Dicynodon and similar dicynodonts found in Laos.
