Anteosaur

From Wikipedia, the free encyclopedia

iAnteosaur
Fossil range: Wordian to Capitanian

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Synapsida
Order:	Therapsida
Suborder:	Dinocephalia
Superfamily:	Anteosauroidea Boonstra, 1962

Families

Anteosauridae
Brithopodidae
Deuterosauridae
Syodontidae
?Stenocybidae

Anteosaurs are a group of large, primitive carnivorous Dinocephalians (early "mammal-like reptiles"), with huge canines and incisors and short limbs, that are known from the Middle Permian of South Africa, Russia, and China. The largest grew to very large size, with skulls 50 to 80 cm long, and were the largest predators of their time. They died out at the end of the Middle Permian, possibly as a result of the extinct of the herbivorous Tapinocephalia on which they fed.

1 Characteristics
2 History of classification
3 Evolutionary relationships
4 References
5 Links

[edit] Characteristics

The Anteosauria are destinguished from the Tapinocephalia by a number of features, such as very large canines, cheek teeth with bulbous crowns, and an upturning of the premaxilla, so that the front of mouth curves strongly upwards. The limbs are short and the skull long, narrow, and heavy. The temporal opening is much larger than in the early Biarmosuchia, indicating larger jaw muscles and a stronger bite. There is a tendencty especially in more advanced forms such as Anteosaurus towards thickeniung of the bones of the top of the skull, indicating head-butting behaviour. The tail is very long in at least some genera.

[edit] History of classification

The group was originally defined as a superfamily by L. D. Boonstra in 1962 to include the families Brithopodidae and Anteosauridae

James Hopson and Herbert Barghusen in 1986 provided the first cladistic study of the Therapsida. They used the term "Anteosauria" and synonymised the families Brithopodidae and Anteosauridae. They sugggested the following schema:

             ,----------------------------------Syodon
             |
ANTEOSAURIA--|                 ,----------------Titanophoneus
(=Anteosaur- |                 |
  idae)      `--ANTEOSAURINAE--|                
                               |                ,--Doliosaurus
                               `--ANTEOSAURINI--|
                                                `--Anteosaurus

(see Hopson & Barghusen 1986 p.91)

Gillian King in a 1988 review of the Anomodontia (including the Dinocephalia - however the view that the Dinocephalia are a subset of the Anomodontia is no longer held) as part of Gutsav Fischer Verlag's ongoing Encyclopedia of Paleoherpetology series of volumes, uses a more traditional Linnaean arrangement, but includes the herbivorous forms under the superfamily Anteosauroidea as well:

Superfamily Anteosauroidea BOONSTRA 1962
    Family Brithopidae BOONSTRA 1972
      Subfamily Brithopodinae EFREMOV 1954
      Subfamily Anteosaurinae 1954
    Family Titanosuchidae BOONSTRA 1972
      Subfamily Titanosuchinae BROOM 1903
      Subfamily Tapinocephalinae LYDEKKER 1890

Note that the "Titanosuchidae" here is equivalent to the "Tapinocephalia".

Finally, as part of a much larger Therapsid cladogram, Bruce Rubidge and Christian Sidor in 2001 offer the following:

  ,----------------- Stenocybus
  |
--|    ,------------ Australosyodon  
  |    |
  |    |------------ Syodon
  `----|                
       |      ,----- Titanophoneus
       `------|
              `----- Anteosaurus

[edit] Evolutionary relationships

The early Russian (Boonstra 1972) and Chinese (Rubidge & Sidor 2001) Anteosaurs are generally considered the most primitive of the Dinocephalia, and hence of the Eutheropoda (in which case they may constitute a paraphyletic assemblage), although it has also been suggested (Kemp, 1982, King 1988) that the Estemmenosuchids are more basal. They have features in common with Pelycosaurs (Carroll 1988) and Biamosuchians (Chudinov 1965), and, with the Tapinocehalia, are part of the first major evolutionary radiation of the Therapsida (Rubidge & Sidor 2001). So far little work has been done on detailed phylogenetic relationships between the various taxa.

[edit] References

Boonstra, L.D., 1972, Discard the names Theriodontia and Anomodontia: a new classification of the Therapsida. Annals of the South African Museum 59:315-338.
Carroll, R. L., 1988, Vertebrate Paleontology and Evolution, WH Freeman & Co.
Chudinov, P. K. 1965, "New Facts about the Fauna of the Upper Permian of the USSR", Journal of Geology, 73:117-30
Hopson, J.A. and Barghusen, H.R., 1986, An analysis of therapsid relationships in N Hotton, III, PD MacLean, JJ Roth and EC Roth, The Ecology and Biology of Mammal-like Reptiles, Smithsonian Institute Press, pp. 83-106
King, G.M., 1988, "Anomodontia" Part 17 C, Encyclopedia of Paleoherpetology, Gutsav Fischer Verlag, Stuttgart and New York,
Rubidge, B.S. & Sidor, C.A. 2001, Evolutionary patterns among Permo-Triassic therapsids. Ann. Rev. Ecol. Syst. 32: 449-480.