Bradysaurus is a genus of large, primitive pareiasaur. They possessed a covering of armoured scutes, likely serving as defense against predators. Fossils of Bradysaurus are known from the Tapinocephalus Assemblage Zone (Capitanian age) of the South African Karoo. Along with the similarly large dinocephalia, the bradysaurs constituted the herbivorous megafauna of the late Middle Permian Period in the region.

Description

thumb|left|B. baini

thumb|left|B. seeleyi

Bradysaurus was in length, with a 2023 study estimating a body mass of (average ), for Bradysaurus baini based on a virtual sculpted model, comparable to a cow. The skull was large (about 42 to 48 centimeters long), broad and rounded at the front. It was coarsely sculptured and knobby, with the sutures between the bones not clearly visible.

The marginal teeth were high-crowned, with only a few cusps, which is a primitive characteristic. The feet were short and broad, the phalangeal count being 2,3,3,3,2 on the fore-foot and 2,3,3,4,3 on the hind. The whole body is protected by dermal scutes, although these are not as thick or heavy as in more advanced forms.

Classification and species

Bradysaurus is the only member of the subfamily Bradysaurinae. It is the most primitive known pareiasaur and can be considered a good ancestral type from which the others developed. Its large dimensions show that, even very early in their evolutionary history, these strange animals had already attained an optimal size. Even later, more advanced forms, like Scutosaurus, were no larger. The advantage of large size was to provide defense against predators and to maintain a stable body temperature (gigantothermy).

Kuhn 1969 lists no fewer than nine species for this genus, but this is certainly an excessive number. Boonstra 1969 distinguishes only four species on the basis of tooth structure, two of which Kuhn places in the genus Embrithosaurus.

Bradysaurus seeleyi

B. seeleyi (Haughton and Boonstra, 1929) is from the Tapinocephalus zone, Lower Beaufort Beds, Karoo basin, South Africa. This is a less common form. Boonstra, 1969, considered this a valid species of Bradysaurus

References

  • Edwin H. Colbert, 1965, The Age of Reptiles, The World Naturalist, Weidenfeld and Nicolson, London, pp. 52–3
  • Barry Cox, R.J.G. Savage, Brian Gardiner, Dougal Dixon, 1988, Illustrated Encyclopaedia of Dinosaurs and Prehistoric Animals
  • Carroll Lane Fenton and Mildred Adams Fenton, 1958, The Fossil Book, Doubleday & Co., Garden City, New York, p. 306
  • Bradysaurs at Palaeos