[1] The first fossils to be found in the Beaufort Group rocks that encompass the current eight biozones were discovered by Andrew Geddes Bain in 1856.

[10] This informal three-part subdivision scheme was later labelled with letters (as subzones A, B, and C from oldest to youngest) until it was formalized with robust index taxa and type sections in 2020.

[13] The Cynognathus Assemblage Zone contains argillaceous mudstone successions varying from maroon to reddish, blueish-green, and greyish-green in colour.

The environment during time of deposition was semi-arid, but with seasonal rain and flooding due to the presence of crevasse splays in the mudstone layers.

[15] The thickest outcrops of the Cynognathus Assemblage Zone, reaching approximately 600 metres (2,000 ft), occur between Queenstown and Lady Frere in the Eastern Cape.

Sediments of Subzone A are likely present in the Eastern Cape, though a lack of sufficient fossil material prevents it from being distinguished from younger strata.

Subzone B reaches up to 500 m thick at the stratotype between Queenstown and Lady Frere, thinning northwards until it disappears east of Thaba 'Nchu.

The large dicynodont Kannemeyeria simocephalus[22] appears in Subzone B alongside other anomodonts, and therocephalian species can be found throughout the biozone.

Plant fossils such as Dicroidium, Dadoxylon, and Schizoneura have been uncovered from limited areas corresponding to Subzones B - C. Aquatic life is well represented: numerous species of temnospondyl amphibian, fishes, rare occurrences of molluscs, and ichnofossils of arthropod trackways and vertebrate burrows have been discovered.

Its base is defined by the first appearance of Cynognathus crateronotus, as well as the trirachodontid cynodont Langbergia modisei and the erythrosuchid archosauriform Garjainia madiba.

Alongside abundant fossils of Cynognathus crateronotus, the base of Subzone B sees the first appearance of fellow cynodonts Diademodon tetragonus and Trirachodon berryi.

Other species with utility for correlation include the temnospondyl Paracyclotosaurus morganorum and the dicynodont Shansiodon sp., which co-occur in the lower part of the subzone.

[1] Cynognathus and Diademodon fossils have even been found in the Río Seco de la Quebrada Formation of Mendoza Province, Argentina.

[1] However, there is some debate over their age; one ash bed below the Rio Seco de la Quebrada Formation was radiometrically dated to around 236 Ma (early Carnian), much younger than previously suggested purely based on tetrapod biostratigraphy.

[33] The classic Cynognathus Assemblage Zone has been equated with the Nonesian Land Vertebrate Faunachron, part of a heavily-debated global system of Triassic tetrapod biostratigraphy.