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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

B. baini
B. seeleyi

Bradysaurus was 2.5–3 m (8 ft 2 in – 9 ft 10 in) in length, with a 2023 study estimating a body mass of 851.4–1,276.5 kilograms (1,877–2,814 lb) (average 1,022 kilograms (2,253 lb)), for Bradysaurus baini based on a virtual sculpted model, comparable to a cow.[1] 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.[2] Boonstra 1969 distinguishes only four species on the basis of tooth structure,[3] two of which Kuhn places in the genus Embrithosaurus.[2] The genera Brachypareia, Bradysuchus, Koalemasaurus, and Platyoropha are synonyms of Bradysaurus.

Bradysaurus baini

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.[4]

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[3] and Lee, 1997,[4] 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.

Phylogeny

Bradysaurus is the titular member of Bradysauria, a group of large, early diverging pareiasaurs known from the Middle Permian of South Africa alongside Embrithosaurus and Nochelesaurus.[1] Cladogram after Li & Yun, 2025:[5]

Pareiasauria

References

  1. ^ a b Van den Brandt, Marc Johan; Day, Michael Oliver; Manucci, Fabio; Viglietti, Pia Alexa; Angielczyk, Kenneth David; Romano, Marco (2023-02-27). “First volumetric body mass estimate and a new in vivo 3D reconstruction of the oldest Karoo pareiasaur Bradysaurus baini, and body size evolution in Pareiasauria”. Historical Biology. 36 (3): 587–601. doi:10.1080/08912963.2023.2175211. ISSN 0891-2963. S2CID 257369904. Archived from the original on 2023-08-04. Retrieved 2023-04-04.
  2. ^ a b Khun, Oskar (1969). “Cotylosauria”. Handbuch der Palaoherpetologie [Encyclopedia of Palaeoherpetology]. Stuttgart: Gustav Fischer Verlag.
  3. ^ a b Boonstra, Lieuwe Dirk (1969). “The Fauna of the Tapinoephalus Zone (Beaufort Beds of the Karoo)”. Ann. S. Afr. Mus. 56 (1): 29–32.
  4. ^ a b Lee, MSY (1997). “Pareiasaur phylogeny and the origin of turtles”. Zool. J. Linnean Soc. (120): 197–280.
  5. ^ Yi, Jian; Liu, Jun (2025-06-04). “The tetrapod fauna of the upper Permian Naobaogou Formation of China: a new mid-sized pareiasaur Yinshanosaurus angustus and its implications for the phylogenetic relationships of pareiasaurs”. Papers in Palaeontology. 11 (3). doi:10.1002/spp2.70020. ISSN 2056-2799.
  • 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