|Skull and neck vertebrae of Thrinaxodon liorhinus in CosmoCaixa Barcelona|
|Family:||† Thrinaxodontidae |
Watson and Romer, 1956
Thrinaxodontidae is an extinct family of cynodonts that includes the genera Thrinaxodon , Nanictosaurus , Nanocynodon , and Novocynodon , and possibly Bolotridon and Platycraniellus .All thrinaxodontids share a bony secondary palate. Thrinaxodontids are basal members of the cynodont clade Epicynodontia. Some studies consider the family a paraphyletic group, representing an evolutionary grade of basal epicynodonts rather than an actual clade.
Therapsida is a major group of eupelycosaurian synapsids that includes mammals and their ancestors. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more underneath the body, as opposed to the sprawling posture of many reptiles and salamanders. The earliest fossil attributed to Therapsida is Tetraceratops insignis from the Lower Permian.
The cynodonts are therapsids that first appeared in the Late Permian. Mammals are cynodonts, as are their extinct ancestors and close relatives. All other cynodont lines went extinct.
Thrinaxodon is an extinct genus of cynodonts, most commonly regarded by its species T. liorhinus which lived in what are now South Africa and Antarctica during the Early Triassic. Thrinaxodon lived just after the Permian–Triassic mass extinction event, its survival during the extinction may have been due to its burrowing habits.
Galesaurus was a prehistoric carnivorous therapsid that lived between the Induan and the Olenekian age in what is now South Africa. It was incorrectly classified as a dinosaur by Sir Richard Owen in 1859.
Mammaliaformes ("mammal-shaped") is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recent common ancestor of Morganucodonta and the crown group mammals; the latter is the clade originating with the most recent common ancestor of extant Monotremata, Marsupialia, and Placentalia. Besides Morganucodonta and the crown group mammals, Mammaliaformes includes Docodonta and Hadrocodium as well as the Triassic Tikitherium, the earliest known member of the group.
Dvinia is an extinct genus of cynodonts of the family Dviniidae found in the Salarevo Formation of Sokolki on the Northern Dvina River near Kotlas in Arkhangelsk Oblast, Russia. Its fossil remains date from the Late Permian and were found with Inostrancevia, Scutosaurus and Vivaxosaurus.
The theriodonts or Theriodontia are a major group of therapsids. They can be defined in traditional, Linnaean terms, in which case they are a suborder of synapsids that lived from the Middle Permian to the Middle Cretaceous, or in cladistic terms, in which case they include not only the traditional theriodonts but also their descendants the mammals as well.
Procynosuchus is an extinct genus of cynodonts from the Late Permian. It is considered to be one of the earliest and most basal cynodonts. It was 60 cm (2 ft) long and seems to have been adapted to a semi-aquatic lifestyle.
Cynognathia is one of two major clades of cynodonts, the other being Probainognathia. Cynognathians included the large carnivorous genus Cynognathus and the herbivorous traversodontids. Cynognathians can be identified by several synapomorphies including a very deep zygomatic arch that extends above the middle of the orbit. The cynognathians are the longest-lived non-mammalian therapsid clade extending from Triassic to the Late Triassic.
Galesauridae is an extinct family of cynodonts. Along with the family Thrinaxodontidae and the large clade Eucynodontia, it makes up the unranked taxon called Epicynodontia. Galesaurids first appeared in the very latest Permian period, just a million years before the greatest extinction of all time, the Permian-Triassic extinction event.
Tritylodontidae is an extinct family of small to medium-sized, highly specialized mammal-like cynodonts, bearing several mammalian traits like erect limbs, endothermy and details of the skeleton. They were the last-known family of the non-mammalian synapsids, persisting into the Early Cretaceous.
Traversodontidae 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 and became extinct in the Early Jurassic diversifying in the Late Triassic. The family Traversodontidae was created by Friedrich von Huene in 1936 for cynodonts first found in São Pedro do Sul in Paleorrota, Brazil.
Theriognathus is an extinct genus of therocephalian therapsid belonging to the family Whaitsiidae, from South Africa and Tanzania. Theriognathus has been dated as existing during the Late Permian. Although Theriognathus means mammal jaw, the lower jaw is actually made up of several bones as seen in modern reptiles, in contrast to mammals. Theriognathus displayed many different reptilian and mammalian characteristics. For example, Theriognathus had canine teeth like mammals, and a secondary palate, multiple bones in the mandible, and a typical reptilian jaw joint, all characteristics of reptiles. It is speculated that Theriognathus was either carnivorous or omnivorous based on its teeth, and was suited to hunting small prey in undergrowth. This synapsid adopted a sleek profile of a mammalian predator, with a narrow snout and around 1 meter long. Theriognathus is represented by 56 specimens in the fossil record.
Progalesaurus is an extinct genus of galesaurid cynodont from the early Triassic. Progalesaurus is known from a single fossil of the species Progalesaurus lootsbergensis, found in the Lystrosaurus Assemblage Zone of the Balfour Formation. Close relatives of Progalesaurus, other galesaurids, include Galesaurus and Cynosaurus. Galesaurids appeared just before the Permian-Triassic extinction event, and disappeared from the fossil record in the Middle-Triassic.
Platycraniellus is an extinct genus of non-mammalian synapsid. It is a cynodont from the Early Triassic Lystrosaurus Assemblage Zone of the Normandien Formation of South Africa. The genus contains the type species P. elegans.
Gomphodontosuchinae is a subfamily of Triassic traversodontid cynodonts. It includes the genera Gomphodontosuchus, Exaeretodon, Menadon, Protuberum, Ruberodon and Scalenodontoides.
Massetognathinae is an extinct subfamily of cynodonts in the family Traversodontidae. It includes four species from the Middle and Late Triassic: Massetognathus pascuali from Argentina, Massetognathus ochagaviae and Santacruzodon hopsoni from southern Brazil, and Dadadon isaloi from Madagascar. Massetognathines have several distinguishing characteristics, including flattened skulls, small canine teeth, and postcanine teeth with three cusps on their outer edges. Massetgognathinae was defined by Kammerer et al. (2012) as the clade containing all traversodontids more closely related to Massetognathus pascuali than to Gomphodontosuchus brasiliensis, and is the sister taxon of the traversodontid subfamily Gomphodontosuchinae, which was defined by Kammerer et al. (2008) as all traverodontids more closely related to G. brasiliensis than to M. pascuali.
Gomphodontia is a clade of cynognathian cynodonts that includes the families Diademodontidae, Trirachodontidae, and Traversodontidae. Gomphodonts are distinguished by wide and closely spaced molar-like postcanine teeth, which are convergent with those of mammals. Other distinguishing characteristics of gomphodonts include deep zygomatic arches, upper postcanines with three or more cusps spanning their widths and lower postcanines with two cusps spanning their widths. Gomphodonts first appeared in the Early Triassic and became extinct in the Jurassic. Fossils are known from southern Africa, Argentina and southern Brazil, eastern North America, Europe, China, and Antarctica.
Abdalodon is an extinct genus of late Permian cynodonts, known by its only species A. diastematicus.Abdalodon together with the genus Charassognathus, form the clade Charassognathidae. This clade represents the earliest known cynodonts, and is the first known radiation of Permian cynodonts.
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