[2][3] As a member of the clade Biarmosuchia, Pachydectes retains many basal therapsid features, though with unique specializations one of which is the presence of adornments on the skull with horn-like protuberances.

Pachydectes was initially discovered in 1997 during road construction being collected from just above the Ecca-Beaufort boundary in the Jansenville District of the Eastern Cape Province of South Africa, taking the form of a skull though missing the dentary.

[4] Subsequently Kammerer and Sidor have composed a reanalysis of the relationships between Burnetiamorphs with the discovery of Mobaceras zambeziense showing similarities to the Bullacephalus providing further evidence that Pachydectes is in fact a member of the clade Burnetiid as proposed originally.

Due to the extensive weathering and lateral compression, the premaxilla and septomaxilla are difficult to decipher information from; however, the portions of the skull of the surrounding area do not differ greatly.

This is contrasted with the weathering and erosion of the fossilized specimen leading to a lack of clarity in the attachment of the jaw adductor musculature which prevents from complete understanding of the closure mechanism.

Similarly to the geographic distribution, the stratigraphic range is difficult to determine as there is one known location that the species has been found that being just above the Ecca-Beaufort contact in the eastern Karoo basin.

The sister taxa of Pachydectes are Bullacephalus, Mobaceras, Burnetia, and Niuksenitia all of which are in a polytomy and are part of the clade Burnetiinae which diverged from Proburnetiinae, both of which form Burnetiidae.

[5] Lemurosaurus pricei Lophorhinus Willodenensis Lobalopex Mordax Lende Chiweta Leucocephalus wewersi Paraburnetia sneeubergensis Proburnetia viatkensis Niuksenitia sukhonensis Burnetia mirabilis Mobaceras zambeziense Pachydectes elsi This cladogram is based on the phylogeny described in Kammerer 2021 in which the most recent analysis of Burnetiamoph relationships has come to the conclusion of the figure above.