Therapsida
Encyclopedia
Therapsida is a group of the most advanced synapsid
s, and include the ancestors of mammals. Many of the traits today seen as unique to mammals had their origin within early therapsids, including hair
, lactation
, and an erect posture. The earliest fossil attributed to Therapsida is believed to be Tetraceratops insignis (Lower Permian
). Therapsids evolved from 'pelycosaur
s' (specifically sphenacodonts
) 275 million years ago. They replaced the pelycosaurs as the dominant land animal in the mid Permian, remaining the dominant fauna until replaced by dinosaur
s and their relatives in mid Triassic
. Evolving ever smaller forms under the dinosaurs, they eventually gave rise to mammal
s 200 million years ago, and all non-mammalian therapsids became extinct by the Early Cretaceous
period (146 Ma to 100 Ma).
While the early therapsids had skull
s very similar to those of their pelycosaur
ian ancestors, they differed in the post-cranial skeleton.
s and pelycosaurs. The feet were more symmetrical, with the first and last toes short and the middle toes longer, indication the foots axis was placed parallel to that of the animal, not sprawling out sideways. This would have given a more mammal-like gait than the lizard
-like gait of the pelycosaurs.
s for nipping, great lateral canines
for puncturing and tearing, and molar
s for shearing and chopping food.
from a group of pelycosaurs called sphenacodonts
. Therapsids became the dominant land animals in the Middle Permian
, displacing the pelycosaurs. Therapsida consists of three bigger clades, the dinocephalia
ns, the herbivorous anomodont
s, and the mostly carnivorous theriodont
s, with the carnivorous biarmosuchia
ns as a paraphyletic assemblage of primitive forms. After a brief burst of evolutionary diversity, the dinocephalians died out in the later Middle Permian (Guadalupian) but the anomodont dicynodont
s and the theriodont gorgonopsia
ns and therocephalia
ns flourished, being joined at the very end of the Permian by the first cynodont
s
Like all land animals, the therapsids were seriously affected by the Permian–Triassic extinction event, with the very successful gorgonopsians dying out altogether and the remaining groups, dicynodont
s, therocephalia
ns, and cynodont
s of a few species, each surviving into the Triassic
. The dicynodonts, now represented by a single family of large stocky herbivore
s, the Kannemeyeridae, and the medium-sized cynodonts (including both carnivorous and herbivorous forms), flourished worldwide, throughout the Early and Middle Triassic. They died out across much of Pangea at the end of the Carnian
(Late Triassic), although they continued for some time longer in the wet equatorial band and the south.
Some exceptions were the still further derived eucynodonts. At least three groups of them survived. They all appeared in the Late Triassic
period. The extremely mammal-like family, Tritylodontidae
, survived into the Early Cretaceous
. An extremely mammal-like family, Tritheledontidae, are unknown later than the Early Jurassic
. The third group, Morganucodon
and similar animals, were mammaliformes or the "proto-mammals" (or very early mammals depending of taxonomic preferences).
Some non-eucynodont cynodonts survived the Permian-Triassic extinction, such as Thrinaxodon
but only to become extinct by the Middle Triassic
.
The therocephalia
ns, relatives of the cynodonts, managed to survive the Permian-Triassic extinction and continued to diversify through the Early Triassic
period. Approaching the end of the period, however, the therocephalians were declining to extinction and eventually became extinct, possibly due to climatic changes
and competition from cynodonts and other animal
s struggling to survive.
Dicynodonts have been thought to have become extinct before the end of the Triassic
, but there is evidence that they survived the extinction. Their fossils have been found in Gondwana
. Other animals that were common in the Triassic also took refuge here, such as the temnospondyls. This is an example of Lazarus taxon
.
Mammal
s, the only living therapsids, evolved in the Early Jurassic
period. They radiated from a group of Mammaliaformes
that is related to the symmetrodonts. The Mammaliaformes themselves evolved from probainognathia
ns, a lineage of the eucynodont suborder.
Synapsid
Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...
s, and include the ancestors of mammals. Many of the traits today seen as unique to mammals had their origin within early therapsids, including hair
Hair
Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....
, lactation
Lactation
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
, and an erect posture. The earliest fossil attributed to Therapsida is believed to be Tetraceratops insignis (Lower Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
). Therapsids evolved from 'pelycosaur
Pelycosaur
The pelycosaurs are an informal grouping composed of basal or primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller...
s' (specifically sphenacodonts
Sphenacodontia
Sphenacodontia is the name given to the clade that includes the Sphenacodontidae and all their descendants . They first appear during the Late Pennsylvanian epoch. The defining characteristics include a thickening of the maxilla visible on its internal surface, above the large front teeth; and...
) 275 million years ago. They replaced the pelycosaurs as the dominant land animal in the mid Permian, remaining the dominant fauna until replaced by dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s and their relatives in mid Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
. Evolving ever smaller forms under the dinosaurs, they eventually gave rise to mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s 200 million years ago, and all non-mammalian therapsids became extinct by the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
period (146 Ma to 100 Ma).
Characteristics
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
s very similar to those of their pelycosaur
Pelycosaur
The pelycosaurs are an informal grouping composed of basal or primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller...
ian ancestors, they differed in the post-cranial skeleton.
Legs and feet
Their legs are positioned more vertically beneath their bodies than are the sprawling legs of reptileReptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s and pelycosaurs. The feet were more symmetrical, with the first and last toes short and the middle toes longer, indication the foots axis was placed parallel to that of the animal, not sprawling out sideways. This would have given a more mammal-like gait than the lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
-like gait of the pelycosaurs.
Jaw and teeth
Therapsids' temporal fenestrae are greater than those of the pelycosaurs. The jaws of therapsids are more complex and powerful, and the teeth are differentiated into frontal incisorIncisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s for nipping, great lateral canines
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
for puncturing and tearing, and molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
s for shearing and chopping food.
Evolutionary history
Therapsids evolvedEvolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
from a group of pelycosaurs called sphenacodonts
Sphenacodontia
Sphenacodontia is the name given to the clade that includes the Sphenacodontidae and all their descendants . They first appear during the Late Pennsylvanian epoch. The defining characteristics include a thickening of the maxilla visible on its internal surface, above the large front teeth; and...
. Therapsids became the dominant land animals in the Middle Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
, displacing the pelycosaurs. Therapsida consists of three bigger clades, the dinocephalia
Dinocephalia
Dinocephalia are a clade of large early therapsids that flourished during the Middle Permian, but became extinct leaving no descendants.-Description:...
ns, the herbivorous anomodont
Anomodont
The Anomodontia were a major group of therapsids, an extinct group of animals commonly known as "mammal-like reptiles." They were mostly toothless herbivores. During the Middle Permian they were very diverse, including groups like the Venyukovioidea, the Dromasauria, the Dicynodontia, and early...
s, and the mostly carnivorous theriodont
Theriodont
Theriodonts , are a major group of therapsids. They can be defined in traditional, Linnaean terms, in which case they are a suborder of mammal-like reptiles that lived from the Middle Permian to the Middle Cretaceous, or in Cladistic terms, in which case they include not only the traditional...
s, with the carnivorous biarmosuchia
Biarmosuchia
Biarmosuchia, also known as Eotitanosuchia and Phthinosuchia, is an assemblage of primitive Permian therapsids that represent either a paraphyletic stem group or a very early off-shoot of the main therapsid tree....
ns as a paraphyletic assemblage of primitive forms. After a brief burst of evolutionary diversity, the dinocephalians died out in the later Middle Permian (Guadalupian) but the anomodont dicynodont
Dicynodont
Dicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'...
s and the theriodont gorgonopsia
Gorgonopsia
Gorgonopsia is a suborder of therapsid synapsids. Their name is a reference to the Gorgons of Greek mythology. Like other therapsids, gorgonopsians were at one time called "mammal-like reptiles"...
ns and therocephalia
Therocephalia
Therocephalians are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic 265.0—245.0 Ma existing for approximately ....
ns flourished, being joined at the very end of the Permian by the first cynodont
Cynodont
Cynodontia or cynodonts are a taxon of therapsids which first appeared in the Late Permian and were eventually distributed throughout all seven continents by the Early Triassic . This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of...
s
Like all land animals, the therapsids were seriously affected by the Permian–Triassic extinction event, with the very successful gorgonopsians dying out altogether and the remaining groups, dicynodont
Dicynodont
Dicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'...
s, therocephalia
Therocephalia
Therocephalians are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic 265.0—245.0 Ma existing for approximately ....
ns, and cynodont
Cynodont
Cynodontia or cynodonts are a taxon of therapsids which first appeared in the Late Permian and were eventually distributed throughout all seven continents by the Early Triassic . This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of...
s of a few species, each surviving into the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
. The dicynodonts, now represented by a single family of large stocky herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s, the Kannemeyeridae, and the medium-sized cynodonts (including both carnivorous and herbivorous forms), flourished worldwide, throughout the Early and Middle Triassic. They died out across much of Pangea at the end of the Carnian
Carnian
The Carnian is the lowermost stage of the Upper Triassic series . It lasted from about 228.7 till 216.5 million years ago . The Carnian is preceded by the Ladinian and is followed by the Norian...
(Late Triassic), although they continued for some time longer in the wet equatorial band and the south.
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
period. The extremely mammal-like family, Tritylodontidae
Tritylodontidae
Tritylodontids were small to medium-sized, highly specialized and extremely mammal-like cynodonts. They were the last family of the non-mammalian synapsids. One of the last cynodont lines to appear, the Tritylodontidae descended from a Cynognathus-like cynodont...
, survived into the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
. An extremely mammal-like family, Tritheledontidae, are unknown later than the Early Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
. The third group, Morganucodon
Morganucodon
Morganucodon is an early mammalian genus which lived during the Late Triassic. It first appeared about 205 million years ago. This has also been identified with Eozostrodon. Unlike many other early mammals, Morganucodon is well represented by abundant and well preserved, though in the vast...
and similar animals, were mammaliformes or the "proto-mammals" (or very early mammals depending of taxonomic preferences).
Some non-eucynodont cynodonts survived the Permian-Triassic extinction, such as Thrinaxodon
Thrinaxodon
Thrinaxodon was a cynodont, an ermine-sized therapsid. Pits on the skull suggest that Thrinaxodon may have had whiskers, and by extension a protective covering of fur. There are suggestions that it was warm-blooded...
but only to become extinct by the Middle Triassic
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided. It spans the time between 245 ± 1.5 Ma and 228 ± 2 Ma...
.
The therocephalia
Therocephalia
Therocephalians are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic 265.0—245.0 Ma existing for approximately ....
ns, relatives of the cynodonts, managed to survive the Permian-Triassic extinction and continued to diversify through the Early Triassic
Early Triassic
The Early Triassic is the first of three epochs of the Triassic period of the geologic timescale. It spans the time between 251 ± 0.4 Ma and 245 ± 1.5 Ma . Rocks from this epoch are collectively known as the Lower Triassic, which is a unit in chronostratigraphy...
period. Approaching the end of the period, however, the therocephalians were declining to extinction and eventually became extinct, possibly due to climatic changes
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
and competition from cynodonts and other animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s struggling to survive.
Dicynodonts have been thought to have become extinct before the end of the Triassic
Triassic-Jurassic extinction event
The Triassic–Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, , and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas a whole class and twenty percent of all marine families...
, but there is evidence that they survived the extinction. Their fossils have been found in Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
. Other animals that were common in the Triassic also took refuge here, such as the temnospondyls. This is an example of Lazarus taxon
Lazarus taxon
In paleontology, a Lazarus taxon is a taxon that disappears from one or more periods of the fossil record, only to appear again later. The term refers to the account in the Gospel of John, in which Jesus raised Lazarus from the dead...
.
Mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, the only living therapsids, evolved in the Early Jurassic
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
period. They radiated from a group of Mammaliaformes
Mammaliaformes
Mammaliaformes is a clade that contains the mammals and their closest extinct relatives. Phylogenetically, it is defined as a clade including the most recent common ancestor of Sinoconodon, morganuconodonts, docodonts, Monotremata, Marsupialia, Placentalia, extinct members of this clade, and all...
that is related to the symmetrodonts. The Mammaliaformes themselves evolved from probainognathia
Probainognathia
The Probainognathians are one of the two major clades of the infraorder Eucynodontia, the other being Cynognathians. They were mostly carnivorous, though some species may have evolved omnivorous traits. The Probainognathia form into four groups: Probainognathidae, Chiniquodontidae,...
ns, a lineage of the eucynodont suborder.
Classification
- Class Synapsida
- ORDER THERAPSIDA *
- ?Family †Tetraceratopsidae
- Suborder †BiarmosuchiaBiarmosuchiaBiarmosuchia, also known as Eotitanosuchia and Phthinosuchia, is an assemblage of primitive Permian therapsids that represent either a paraphyletic stem group or a very early off-shoot of the main therapsid tree....
*- Family †Biarmosuchidae
- Family †Eotitanosuchidae
- Eutherapsida
- Suborder †DinocephaliaDinocephaliaDinocephalia are a clade of large early therapsids that flourished during the Middle Permian, but became extinct leaving no descendants.-Description:...
- Family †EstemmenosuchidaeEstemmenosuchidaeEstemmenosuchidae are a family of large, very early herbivorous mammal-like reptiles that flourished during the Middle Permian period. They are distinguished by horn-like structures, probably for display or agonistic behavior. Apart from the best known genus, Estemmenosuchus, the group is poorly...
- ?Infraorder †Anteosauria
- Family †AnteosauridaeAnteosauridaeThe Anteosauridae or Anteosaurinae are a family or subfamily of very large carnivorous Dinocephalia that are known from the Middle Permian of Russia and South Africa...
- Family †BrithopodidaeBrithopodidaeBrithopodidae are a paraphyletic family of primitive mostly carnivorous Dinocephalians known from the Middle Permian of Russia. Nowadays the name is used less often, being replaced by Anteosauria Brithopodidae are a paraphyletic family of primitive mostly carnivorous Dinocephalians known from the...
- Family †Deuterosauridae
- Family †SyodontidaeSyodontidaeSyodontidae are a possibly paraphyletic family of smallish primitive carnivorous Dinocephalia. They lack the distinctive 'boss' on the lower jaw, that characterises the Anteosauridae, so they can be considered more primitive. They are known from the Middle Permian Period of what is now Russia...
- ?Family †Stenocybidae
- Family †Anteosauridae
- †TapinocephaliaTapinocephaliaThe tapinocephalians are one of the major groups of dinocephalian therapsids. Unlike anteosaurs and estemmenosuchids, tapinocephalians are mainly from Africa and only one species is found in the north - Ulemosaurus from Russia. The tapinocephalians are divided into three clades, Styracocephalidae,...
- Family †Styracocephalidae
- Family †TapinocephalidaeTapinocephalidaeTapinocephalidae is an advanced family of tapinocephalians. They were all herbivores. They were giants of their time, weighing from 500 to 1000 kg and possibly over 1 or 2 tonnes in weight. They are known from South Africa and Russia. The tapinocephalid skull is very thick, probably used for...
- Family †TitanosuchidaeTitanosuchidaeThe titanosuchids were carnivorous to omnivorous tapinocephalid dinocephalians. As with other tapinocephalids, they had thick-skulls probably for head-butting. They appeared in the Middle Permian. They had large canine teeth, and their incisors were very strong...
- Family †Estemmenosuchidae
- NeotherapsidaNeotherapsidaNeotherapsida is a clade of therapsids. It includes anomodonts and the more derived theriodonts, which include mammals.-Permian:In the Permian time period, Neotherapsids lived in Germany, India, Madagascar, Niger, South Africa, Tanzania, United Kingdom, United States in Texas, and...
- Suborder †AnomodontAnomodontThe Anomodontia were a major group of therapsids, an extinct group of animals commonly known as "mammal-like reptiles." They were mostly toothless herbivores. During the Middle Permian they were very diverse, including groups like the Venyukovioidea, the Dromasauria, the Dicynodontia, and early...
ia *- Superfamily †Venyukoviamorpha
- Family †Otsheridae
- Family †VenyukoviidaeVenyukoviaVenyukovia is an extinct genus of anomodont....
- Infraorder †DromasauriaDromasauriaDromasaurs are a paraphyletic group of anomodont therapsids from the Middle Permian. They were small with slender legs long tails. Their skulls were short, but the eye sockets were large. Dromasauria was once considered to be a major group of basal anomodonts along with the infraorder Venyukovioidea...
- Family †Galeopidae
- Infraorder †DicynodontDicynodontDicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'...
a- Family †Endothiodontidae
- Family †Eodicynodontidae
- Family †Kingoriidae
- (unranked) †DiictodontiaDiictodontiaThe Diictodontia were a group of herbivorus Dicynodonts from the Permian of South Africa. This infraorder was composed of three different families; Diictodontidae , Emydopidae, and Robertiidae....
- Superfamily †Emydopoidea
- Family †Cistecephalidae
- Family †Emydopidae
- Superfamily †Robertoidea
- Family †Diictodontidae
- Family †Robertiidae
- Superfamily †Emydopoidea
- (unranked) †PristerodontiaPristerodontiaPristerodontia is a group of dicynodont therapsids that includes cryptodontids, geikiids, lystrosaurids, kannemeyeriids, and other related forms. Pristerodontians were one of the few groups of dicynodonts to survive the Permian-Triassic extinction event, diversifying in the Triassic....
- Family †Aulacocephalodontidae
- Family †Dicynodontidae
- Family †KannemeyeriidaeKannemeyeriidaeKannemeyeriidae is a family of large, stocky, beaked and sometimes tusked dicynodonts. They were the dominant large terrestrial herbivores through most of the Triassic period...
- Family †LystrosauridaeLystrosauridaeLystrosauridae was a family of Synapsids from the Permian and Triassic time periods.-Distribution:-Triassic Distribution:In the Triassic period, Lystrosaurids lived in Antarctica and China.-Relatives:...
- Family †Oudenodontidae
- Family †Pristerodontidae
- Family †Shanisiodontidae
- Family †Stahleckeriidae
- Superfamily †Venyukoviamorpha
- TheriodontTheriodontTheriodonts , are a major group of therapsids. They can be defined in traditional, Linnaean terms, in which case they are a suborder of mammal-like reptiles that lived from the Middle Permian to the Middle Cretaceous, or in Cladistic terms, in which case they include not only the traditional...
ia *- Suborder †GorgonopsiaGorgonopsiaGorgonopsia is a suborder of therapsid synapsids. Their name is a reference to the Gorgons of Greek mythology. Like other therapsids, gorgonopsians were at one time called "mammal-like reptiles"...
- Family †GorgonopsidaeGorgonopsiaGorgonopsia is a suborder of therapsid synapsids. Their name is a reference to the Gorgons of Greek mythology. Like other therapsids, gorgonopsians were at one time called "mammal-like reptiles"...
- Family †Gorgonopsidae
- Eutheriodontia
- Suborder †TherocephaliaTherocephaliaTherocephalians are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic 265.0—245.0 Ma existing for approximately ....
- Family †Lycosuchidae
- (unranked) †ScylacosauriaScylacosauriaScylacosauria is a clade of therocephalian therapsids. It includes the basal family Scylacosauridae and the infraorder Eutherocephalia. Scylacosauridae and Eutherocephalia form this clade to the exclusion of Lycosuchidae, the most basal therocephalian family. Thus, Scylacosauria includes all...
- Family †ScylacosauridaeScylacosaurusScylacosaurus is an extinct genus of therapsid....
- Family †Scylacosauridae
- Infraorder †EutherocephaliaEutherocephaliaEutherocephalia is an infraorder of therocephalian therapsids. Eutherocephalians are distinguished from the lycosuchids and scylacosaurids, two early therocephalian families. While lycosuchids and scyalosaurids went extinct by the end of the Permian period, eutherocephalians survived the...
- Family †HofmeyriidaeHofmeyriidaeHofmeyriidae is a family of therocephalian therapsids. It includes the genera Hofmeyria and Ictidostoma.-External links:* in the Paleobiology Database...
- Family †MoschorhinidaeMoschorhinidaeAkidnognathidae is a family of small therocephalian therapsids.-Ecology:Akidnognathids were carnivores, hunting prey such as Dicynodonts....
- Family †Whaitsiidae
- Superfamily Bauriodea
- Family †BauriidaeBauriidaeBauriidae is a family of therocephalian therapsids. Bauriids are among the most advanced eutherocephalians and possess several mammal-like features such as a secondary palate. Unlike other therocephalians, bauriids were herbivorous. Two subfamilies are classified within Bauriidae:...
- Family †Ericiolacteridae
- Family †Ictidosuchidae
- Family †Ictidosuchopsidae
- Family †Lycideopsidae
- Family †Bauriidae
- Family †Hofmeyriidae
- Suborder Cynodontia *
- Family †Dviniidae
- Family †ProcynosuchidaeProcynosuchidaeProcynosuchidae, along with Dviniidae, were the earliest cynodonts. They appeared around 260 million years ago, and were most abundant during the latest Permian time , shortly before the Permian-Triassic extinction event...
- (unranked) Epicynodontia
- Family †GalesauridaeGalesauridaeGalesauridae, along with the family Thrinaxodontidae and the large clade Eucynodontia make up the unranked taxon called Epicynodontia...
- Family †Thrinaxodontidae
- Infraorder EucynodontiaEucynodontiaEucynodontia is a grouping of animals that includes both mammals, such as dogs, and mammal-like non-mammalian therapsids such as cynodonts . Its membership was and is made up of both carnivores and herbivores. The chronological range extends from at least the Lower Triassic, possibly the Upper...
- (unranked) †Cygnognathia
- Family †Cynognathidae
- Family †Diademodontidae
- Family †TraversodontidaeTraversodontidaeTraversodontidae is a family of herbivorous cynodonts. Traversodonts were primarily Gondwanan, with many species known from Africa and South America. Recently, traversodonts have also been found from Europe and eastern North America. Traversodonts first appeared in the Middle Triassic, diversified...
- Family †TrirachodontidaeTrirachodontidaeTrirachodontidae is an extinct family of cynognathian cynodonts from the Triassic of China and southern Africa. Trirachodontids appeared during the Early Triassic soon after the Permian-Triassic extinction event and quickly spread over a wide geographic area in a comparatively brief amount of time...
- Family †TritylodontidaeTritylodontidaeTritylodontids were small to medium-sized, highly specialized and extremely mammal-like cynodonts. They were the last family of the non-mammalian synapsids. One of the last cynodont lines to appear, the Tritylodontidae descended from a Cynognathus-like cynodont...
- (unranked) ProbainognathiaProbainognathiaThe Probainognathians are one of the two major clades of the infraorder Eucynodontia, the other being Cynognathians. They were mostly carnivorous, though some species may have evolved omnivorous traits. The Probainognathia form into four groups: Probainognathidae, Chiniquodontidae,...
- Family †Chinquodontidae
- Family †ProbainognathidaeProbainognathidaeProbainognathidae is an extinct family of meat-eating mammal-like reptiles which lived during the Upper Triassic. According to some authors, it has perhaps two known members: Probainognathus from South America, and the somewhat later Lepagia from Europe. The family was established by Romer in 1973...
- (unranked) †Ictidosauria
- Family †Tritheledontidae
- (unranked) Mammaliformes
- Class MammalMammalMammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ia
- Class Mammal
- (unranked) †Cygnognathia
- Family †Galesauridae
- Suborder †Therocephalia
- Suborder †Gorgonopsia
- Suborder †Anomodont
- Suborder †Dinocephalia
Phylogeny
External links
- "Therapsida: Mammals and extinct relatives" Tree of Life
- "Therapsida: overview" Palaeos