Bradysaurus BW.jpg

''Bradysaurus'' was a large, early and common pareiasaur, the fossils of which 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 life they were probably slow, clumsy and inoffensive animals, that had evolved a covering of armoured scutes to protect them against their predators, the gorgonopsians.

Description

''Bradysaurus'' was in length and half a tonne to a tonne in weight. 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''. The genera ''Brachypareia'', ''Bradysuchus'', ''Koalemasaurus'', and ''Platyoropha'' are synonyms of ''Bradysaurus''.

''B. baini'' (Seeley, 1892) is from the ''Tapinocephalus'' zone, Lower Beaufort Beds, Karoo basin, South Africa. This is the type species for the genus. The quadra-jugal region (cheek-bones) were only moderately developed. The snout was broad and rounded and there were 15 or 16 pairs of overlapping teeth in each jaw. This animal could be considered a generic early pareiasaur. According to Lee, 1997, the available material of ''B. baini'' lacks distinguishing autapomorphies or characteristics.

''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'' and Lee, 1997, considers this animal a sister group to more advanced pareiasaurs. ''B. seelyi'' seems to be closely related to ''Nochelesaurus'' and ''Embrithosaurus''. In contrast to the more numerous but similarly sized ''B. baini'', the cheekbones were heavy and greatly enlarged. There were 19 or 20 pairs of strongly overlapping teeth on each jaw.

References

* Boonstra, L. D. 1969, "The Fauna of the Tapinoephalus Zone (Beaufort Beds of the Karoo)," Ann. S. Afr. Mus. 56 (1) 1-73, pp. 29–32
* 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
* Kuhn, O, 1969, Cotylosauria, part 6 of ''Handbuch der Palaoherpetologie'' (Encyclopedia of Palaeoherpetology), Gustav Fischer Verlag, Stuttgart & Portland,
* Lee, MSY (1997), Pareiasaur phylogeny and the origin of turtles. ''Zool. J. Linnean Soc.'', 120: 197-280

External links

Bradysaurs
at Palaeos

{{Taxonbar, from=Q137709

Pareiasaurs
Permian reptiles of Africa
Fossil taxa described in 1914
Capitanian genus first appearances
Capitanian genus extinctions
Prehistoric reptile genera