Megazostrodon is an extinct Mammaliaform from South Africa that is widely accepted as being one of the first mammals. It is approximately 200 million years old. Megazostrodon rudnerae means, literally, ‘Rudner’s large girdle tooth’ (from the Greek mega-large, zostros-girdle and don-tooth — referring to the founder, Ione Rudner, and the large external cingula, or ridges of the upper molars).