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Diapsida : Archosauromorpha : Archisauriformes

Euparkeria
A close archosaur relative

Lateral view of the skull of Euparkeria

Lateral view of the skull of Euparkeria.
 
Euparkeria is a close relative of the archosaurs, and is known only from a single locality in the Lower Triassic of southern Africa. Most grew to about half a meter in length.

The body form of Euparkeria is unusual in that the relative length of its hind limbs to its forelimbs exceeds that of other comparable reptiles of its time. Some have suggested that Euparkeria may have been "facultatively bipedal" (Carroll 1988), and able to run on two legs for short distances as pictured below.

The systematic position of Euparkeria is problematic. The question of its relationships hinges upon the structure of the ankle joint, a pivotal character in understanding the evolution of archosaurs. Whatever the actual case was, there is general agreement that it is either the sister group to all other Archosauria, or is part of the lineage leading to the dinosaurs.

Dorsal and ventral views of the skull of Euparkeria

Dorsal and ventral views of the skull of Euparkeria.

Skeletal restoration of Euparkeria in a bipedal running posture

Skeletal restoration of Euparkeria in a bipedal running posture.

Sources

  • Carroll, R.L. 1988. Vertebrate Paleontology and Evolution. W.H. Freeman, NY.
  • Cruickshank, A.R.I., and M.J. Benton. 1985. Archosaur ankles and relationships of the thecodontian and dinosaurian reptiles. Nature 317:715-717.
  • Gauthier, J.A. 1986. Saurischian monophyly and the origin of birds. In K. Padian (ed). The Origin of Birds and the Evolution of Flight. Memoirs of the California Academy of Sciences 8:1-55.

Text by Brian R. Speer, 10/1997. Euparkeria images used with permission of the Royal Society of London: from Ewer, R.F. 1965. The anatomy of the thecodont reptile Euparkeria capensis Broom. Philosophical Transactions of the Royal Society of London, B 248:379-435.