| Hofmeyriidae Temporal range: Permian | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Therapsida |
| Clade: | † Therocephalia |
| Clade: | † Eutherocephalia |
| Family: | † Hofmeyriidae Broom, 1935 |
| Genera | |
Hofmeyriidae is a family of therocephalian therapsids. It includes the genus Ictidostoma . [1]
Therapsida is a clade comprising a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. 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, resulting in a more "standing" quadrupedal posture, as opposed to the lower sprawling posture of many reptiles and amphibians.
Sphenacodontia is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes Haptodus baylei, Haptodus garnettensis and Sphenacodon ferox, but not Edaphosaurus pogonias". They first appear during the Late Pennsylvanian epoch. From the end of the Carboniferous to the end of the Permian, most of them remained large, with only some secondarily becoming small in size.
Eupelycosauria is a large clade of animals characterized by the unique shape of their skull, encompassing all mammals and their closest extinct relatives. They first appeared 308 million years ago during the Early Pennsylvanian epoch, with the fossils of Echinerpeton and perhaps an even earlier genus, Protoclepsydrops, representing just one of the many stages in the evolution of mammals, in contrast to their earlier amniote ancestors.
Biarmosuchia is an extinct clade of non-mammalian synapsids from the Permian. Biarmosuchians are the most basal group of the therapsids. They were moderately-sized, lightly built carnivores, intermediate in form between basal sphenacodont "pelycosaurs" and more advanced therapsids. Biarmosuchians were rare components of Permian ecosystems, and the majority of species belong to the clade Burnetiamorpha, which are characterized by elaborate cranial ornamentation.
Therocephalia is an extinct clade of eutheriodont therapsids from the Permian and Triassic periods. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their teeth, suggest that they were carnivores. Like other non-mammalian synapsids, therocephalians were once described as "mammal-like reptiles". Therocephalia is the group most closely related to the cynodonts, which gave rise to the mammals, and this relationship takes evidence in a variety of skeletal features. Indeed, it had been proposed that cynodonts may have evolved from therocephalians and so that therocephalians as recognised are paraphyletic in relation to cynodonts.
Tetraceratops insignis is an extinct synapsid from the Early Permian that was formerly considered the earliest known representative of Therapsida, a group that includes mammals and their close extinct relatives. It is known from a single 90-millimetre-long (3.5 in) skull, discovered in Texas in 1908. According to a 2020 study, it should be classified as a primitive non-therapsid sphenacodont rather than a genuine basal therapsid.
Galechirus is an extinct genus of anomodont therapsids. It was about 30 cm (1 ft) long.
Eutherocephalia is an extinct clade of advanced therocephalian therapsids. Eutherocephalians are distinguished from the lycosuchids and scylacosaurids, two early therocephalian families. While lycosuchids and scyalosaurids became extinct by the end of the Permian period, eutherocephalians survived the Permian–Triassic extinction event. The group eventually became extinct in the Middle Triassic.
Anomocephalus is an extinct genus of primitive anomodonts and belongs to the clade Anomocephaloidea. The name is said to be derived from the Greek word anomos meaning lawless and cephalos meaning head. The proper word for head in Greek is however κεφαλή (kephalē). It is primitive in that it retains a complete set of teeth in both jaws, in contrast to its descendants, the dicynodonts, whose dentition is reduced to only a single pair of tusks, with their jaws covered by a horny beak similar to that of a modern tortoise. However, they are in no way closely related.
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.
Colobodectes is an extinct genus of dicynodont therapsid from the Tapinocephalus Assemblage Zone in the Abrahamskraal Formation, South Africa.
Cistecephaloides is an extinct genus of dicynodont therapsids of the Cistecephalus Assemblage Zone, Beaufort Group of South Africa.
Dimacrodon is an extinct genus of non-mammalian synapsid from the latest Early Permian San Angelo Formation of Texas. It is distinguished by toothless, possibly beaked jaw tips, large lower canines and a thin bony crest on top of its head. Previously thought to be an anomodont therapsid related to dicynodonts, it was later found to lack any diagnostic features of anomodonts or even therapsids and instead appears to be a 'pelycosaur'-grade synapsid of uncertain classification.
Eosyodon is a dubious genus of extinct non-mammalian synapsids from the Permian of Texas. Its type and only species is Eosyodon hudsoni. Though it was originally interpreted as an early therapsid, it is probably a member of Sphenacodontidae, the family of synapsids that includes Dimetrodon.
Glanosuchus is a genus of scylacosaurid therocephalian from the Late Permian of South Africa. The type species G. macrops was named by Robert Broom in 1904. Glanosuchus had a middle ear structure that was intermediate between that of early therapsids and mammals. Ridges in the nasal cavity of Glanosuchus suggest it had an at least partially endothermic metabolism similar to modern mammals.
Knoxosaurus is an extinct genus of non-mammalian synapsids containing the species Knoxosaurus niteckii that existed approximately 279.5 to 268 million years ago. It was named by American paleontologist Everett C. Olson in 1962 on the basis of fragmentary fossils from Middle Permian-age deposits in the San Angelo Formation of Texas in the United States. Olson placed Knoxosaurus in a new infraorder called Eotheriodontia, which he considered a transitional group between the more reptile-like "pelycosaurs" and the more mammal-like therapsids. Knoxosaurus and Olson's other eotheriodonts were later considered to be undiagnostic remains of basal synapsids, no more closely related to therapsids than are other pelycosaur-grade synapsids.
Raranimus is an extinct genus of therapsids of the Middle Permian. It was described in 2009 from a partial skull found in 1998 from the Dashankou locality of the Qingtoushan Formation, outcropping in the Qilian Mountains of Gansu, China. The genus is the most basal known member of the clade Therapsida, to which the later Mammalia belong.
Gorochovetzia is an extinct genus of therocephalian therapsids from the Late Permian of Russia. Fossils have been found in the Gorokhovetsky District of Vladimir Oblast. Gorochovetzia is a member of the family Hofmeyriidae. Its type and only species is G. sennikovi, named in 2011. The skull is short and very robust. The canine teeth are large, while those behind them have enlarged crowns and serrated edges. The lower jaw is deep and curved upward.
Eutheriodontia is a clade of therapsids which appear during the Middle Permian and which includes therocephalians and cynodonts, this latter group including mammals and related forms.
Gorgodon is an extinct genus of basal synapsids. The genus is monotypic, known only from the type species Gorgodon minutus from the Early Permian of the southwestern United States. The only known remains of Gorgodon are two fossils consisting of fragments of the skull. Gorgodon was described and named by paleontologist Everett C. Olson in 1962 from the San Angelo Formation in Knox County, Texas. Based on what is known of Gorgodon—the squamosal, quadrate, and pterygoid bones of the back of the skull, the maxilla and premaxilla bones that make up the front of the skull, and several teeth—Gorgodon had a relatively large temporal fenestra and a pair large, conical caniniform teeth at the front of the jaw. Other distinguishing features of Gorgodon include the fused connection between the quadrate and squamosal bones and a long transverse process of the pterygoid.
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