Homodontosaurus

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Homodontosaurus
Temporal range: Late Permian
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Suborder: Therocephalia
Superfamily: Baurioidea
Genus: Homodontosaurus
Broom, 1949
Type species
Homodontosaurus kitchingi
Broom, 1949

Homodontosaurus is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. The type species Homodontosaurus kitchingi was named by South African paleontologist Robert Broom in 1949. Broom based his description on a small skull found in the Cistecephalus Assemblage Zone near Graaff-Reinet. The skull is very small, at about 55 millimetres (2.2 in) long and 20 millimetres (0.79 in) wide. Homodontosaurus has large eye sockets and an elongated snout. The lower jaw is long, thin, and curved. Numerous small teeth line the upper jaw and are long, pointed, and round in cross-section. [1]

When he first named Homodontosaurus in 1949, Broom considered it to be a pelycosaur. He noted similarities between the skull of Homodontosaurus and that of the sphenacodontid Secodontosaurus from the Early Permian of Texas. Broom thought that Homodontosaurus was most closely related to a pelycosaur called Elliotsmithia , which he named in 1937 on the basis of the back half of a skull. [1] In 1950, South African paleontologist A. S. Brink described a second specimen of Homodontosaurus, which included an articulated postrcranial skeleton. [2] On the basis of this skeleton, paleontologists D. M. S. Watson and Alfred Romer reclassified it as a scaloposaurid therocephalian in 1956. [3] Scaloposaurids are now recognized as an artificial grouping of the juvenile forms of many therocephalians. Homodontosaurus has even been considered the juvenile form of the larger therocephalian Tetracynodon . [4] Homodontosaurus and most other scalopodontids are now classified as basal members of Baurioidea.

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Nanictidopidae Extinct family of therapsids

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Silpholestes is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. The type species Silpholestes jackae was named by South African paleontologist Robert Broom in 1948 from the Cistecephalus Assemblage Zone.

Ictidodraco is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. The type species Ictidodraco longiceps was named by South African paleontologists Robert Broom and John T. Robinson in 1948 from the Cistecephalus Assemblage Zone. Ictidodraco was once classified as a scaloposaurian in the family Silpholestidae. Scaloposauria and Silpholestidae are no longer regarded as valid groups, and Ictidodraco is now classified as a basal member of the clade Baurioidea.

Silphictidoides is an extinct genus of therocephalian therapsids from the Late Permian of Tanzania. The type species Silphictidoides ruhuhuensis was named by German paleontologist Friedrich von Huene in 1950 from the Tropidostoma Assemblage Zone. Silphictidoides was once classified within the family Silpholestidae. Silphedolestids are no longer recognized as a valid grouping, and Silphictidoides is now considered a basal member of the clade Baurioidea.

Polycynodon is an extinct genus of therocephalians from the Late Permian of South Africa. It is known from the Cistecephalus Assemblage Zone. The type species was first described as Octocynodon elegans by South African paleontologist Robert Broom in 1940, but the name Octocynodon was preoccupied by a genus of labrid fish first described in 1904. Along with John T. Robinson, Broom instated Polycynodon as a replacement name for O. elegans in 1948. Polycynodon is classified in Baurioidea, although its relationship to other baurioid therocephalians is uncertain.

Pelictosuchus is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. It is classified in the family Akidnognathidae. The type species Pelictosuchus paucidens was named by South African paleontologist Robert Broom in 1940 from the Dicynodon Assemblage Zone.

Trochosuchidae is an extinct family of therocephalian therapsids from the Permian period. It includes the genera Trochosaurus, Trochosuchus, Trochorhinus, and Hyaenasuchus. Trochosuchids are known only from the Tapinocephalus Assemblage Zone of the Beaufort Group in South Africa. Trochosuchids are basal therocephalians and are similar in appearance to another primitive group of therocephalians, the Scylacosauridae. Compared to scylacosuchids, trochosuchids have broader snouts and more flattened skulls lacking prominent sagittal crests. They have two enlarged canines on either side of the upper jaw, similar to lycosuchid therocephalians but unlike scylacosuchids, which only have one pair of canines.

Ordosiodon is an extinct genus of therocephalian therapsids from the Early Triassic of China. It includes two species, O. lincheyuensis and O. youngi.

Simorhinella is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. It is known from a single species, Simorhinella baini, named by South African paleontologist Robert Broom in 1915. Broom named it on the basis of a single fossil collected by the British Museum of Natural History in 1878 that included the skull and jaws forward from the eye sockets. The skull is unusual in that it has an extremely short and deep snout, unlike the longer and lower snouts of most other therocephalians. Because of the skull's distinctiveness, the classification of Simorhinella within Therocephalia is uncertain. However, a 2014 study proposed that it was closely related to the basal therocephalian Lycosuchus, placing it in the family Lycosuchidae.

References

  1. 1 2 Broom, R. (1949). "New fossil reptile genera from the Bernard Price collection". Annals of the Transvaal Museum. 21 (1–2): 187–194.[ permanent dead link ]
  2. Reisz, R.R.; Dilkes, D.W.; Berman, D.S. (1998). "Anatomy and relationships of Elliotsmithia longiceps Broom, a small synapsid (Eupelycosauria: Varanopseidae) from the Late Permian of South Africa". Journal of Vertebrate Paleontology. 18 (3): 602–611. doi:10.1080/02724634.1998.10011087.
  3. Watson, D.M.S.; Romer, A.S. (1956). "A classification of therapsid reptiles". Bulletin of the Museum of Comparative Zoology. 114 (2): 37–89.
  4. Colbert, E.H.; Kitching, J.W. (1981). "Scaloposaurian reptiles from the Triassic of Antarctica". American Museum Novitates (2709): 1–22. hdl:2246/5362. Archived from the original on 2012-09-19. Retrieved 2012-02-19.