Eodicynodon

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Eodicynodon was the oldest and most primitive member of the dicynodont group, a type of plant-eating therapsid that lived during the middle to late Permian period. It was a small to medium-sized animal, about 0.45 meters long and 0.15 meters high, with tusk-like canines and jaw features used for grinding plant material.

What makes it special is that while it shares many dicynodont traits, it also has some primitive features. For example, its premaxillary bones are paired and not fused, and its vomer bones are also paired. It also had an early version of the dicynodont “cheek pivot system” for chewing, including a double convex jaw joint and a pivot mechanism that helps the mouth close from back to front.

Discovery and name
Eodicynodon was described in 1974 by T. H. Barry. The type species, Eodicynodon oosthuizeni, is named after Roy Oosthuizen, a South African farmer who found the partial skull on his farm in the Cape Province sometime between 1964 and 1970.

Where it lived
Fossils come from the Karoo Supergroup of South Africa, in a rock sequence called the Eodicynodon Assemblage Zone. The Karoo is a famous fossil-rich region that records a long span from the late Carboniferous to the early Jurassic.

Why it matters
As the earliest known dicynodont, Eodicynodon helps scientists understand how dicynodonts evolved from primitive therapsids and how their distinctive chewing system developed. A simplified family tree places it at the base of the dicynodont group, alongside other early relatives.