Gorgonopsia

Gorgonopsians
Temporal range: Middle Permian-Late Permian, 265–252 Ma
Skeleton of Sauroctonus parringtoni
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Order: Therapsida
Clade: Theriodontia
Suborder: †Gorgonopsia
Seeley, 1895
Family: †Gorgonopsidae
Lydekker, 1890
Genera

See below

Gorgonopsia ("Gorgon face") is an extinct suborder of therapsid synapsids. Like other therapsids, gorgonopsians (or gorgonopsids) were at one time called "mammal-like reptiles" as well as "stem mammals".

Description

Their mammalian specializations include differentiated (heterodont) tooth shape, a fully developed temporal fenestra, pillar-like rear legs, a vaulted palate that may have facilitated breathing while holding the prey, and incipiently developed ear bones.[1] Gorgonopsians are a part of a group of therapsids called theriodonts, which includes mammals.[2] They were among the largest carnivores of the late Permian. The largest known, Inostrancevia, was the size of a large bear with a 45 cm long skull, and 12 cm long saber-like teeth (clearly an adaptation to being a carnivore). They likely did not have a full pelage,[3] but whether they had bristles, scales or naked skin is unknown. They possibly had a combination of all of them, as some mammals still do. Like most therapsids, they are assumed to have been terrestrial, and this is supported both by their morphology and bone microanatomy.[4]

Evolutionary history

Gorgonopsians are theriodonts, a major group of therapsids that included the ancestors of mammals. They evolved in the Middle Permian, from a reptile-like therapsid that also lived in that period. The early gorgonopsians were small, being no larger than a dog. The extinction of dinocephalians (which dominated the Middle Permian world) led to gorgonopsids becoming the apex predators of the Late Permian. Some had approached the size of a rhinoceros, such as Inostrancevia, the largest gorgonopsian. A nearly complete fossil of Rubidgea has been found in South Africa.[5][6] The Gorgonopsia became extinct at the end of the Permian period, being the only theriodont line to be terminated by this mass extinction.

Classification

The gorgonopsians are one of the three groups of theriodonts (the other two were the therocephalians, and the cynodonts). Theriodonts are related to the herbivorous Anomodontia. Gorgonopsia includes three subfamilies, the Gorgonopsinae, Rubidgeinae and Inostranceviinae, plus a larger number of genera that have not been placed in any of these groups. A total of 25 genera and 41 species, with the genera described most completely being Dinogorgon, Inostrancevia and Rubidgea.

The most comprehensive review of the group is by Sigogneau-Russell, 1989.

Gebauer (2007) conducted a phylogenetic analysis of gorgonopsians. She did not consider Gorgonopsia and Gorgonopsidae equivalent, and placed only species with autapomorphies, or characteristics unique to those species, in Gorgonopsidae. Aloposaurus, Cyonosaurus, and Aelurosaurus were placed outside Gorgonopsidae as basal gorgonopsids because they did not have autapomorphies. Below is a cladogram from the phylogenetic analysis of Gebauer (2007):[7]

Gorgonopsia 

Aloposaurus

Cyonosaurus

Aelurosaurus


Gorgonopsidae

Scylacognathus

Eoarctops

Gorgonops

Njalila

Lycaenops

Arctognathus

Inostrancevia


Rubidgeinae

Aelurognathus

Rubidgea

Sycosaurus

Clelandina














See also

Wikispecies has information related to: Gorgonopsia

References

  1. ↑ Laurin, M. (1998). New data on the cranial anatomy of Lycaenops (Synapsida, Gorgonopsidae), and reflections on the possible presence of streptostyly in gorgonopsians, Journal of Vertebrate Paleontology 18: 765-776.
  2. ↑ Amson, E., Laurin, M. (2011). On the affinities of Tetraceratops insignis, an Early Permian synapsid, Acta Palaeontologica Polonica 56: 301–312.
  3. ↑ Ruben, J.A.; Jones, T.D. (2000). "Selective Factors Associated with the Origin of Fur and Feathers." (PDF). Amer. Zool. 40 (4): 585–596. doi:10.1093/icb/40.4.585.
  4. ↑ Kriloff, A.; Germain, D.; Canoville, A.; Vincent, P.; Sache, M.; Laurin, M. (2008). "Evolution of bone microanatomy of the tetrapod tibia and its use in palaeobiological inference". Journal of Evolutionary Biology 21 (3): 807–826. doi:10.1111/j.1420-9101.2008.01512.x.
  5. ↑ First complete fossil of fierce prehistoric predator found in South Africa
  6. ↑ ANCIENT TERROR OF EARTH'S PAST UNEARTH IN SOUTH AFRICA
  7. ↑ Gebauer, E.V.I. (2007). Phylogeny and evolution of the Gorgonopsia with a special reference to the skull and skeleton of GPIT/RE/7113 ('Aelurognathus?' parringtoni) (PDF) (Ph.D. thesis). Tübingen: Eberhard-Karls Universität Tübingen. pp. 1–316.

Further reading

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