The genus Nemegtbaatar (Kielan-Jaworowska Z., 1974) is known by the species Nemegtbaatar gobiensis found in the Campanian (Upper Cretaceous) Barun Goyot Formation of Mongolia. "Compared to all extant mammals, the braincase in Nemegtbaatar and Chulsanbaatar is primitive." (Hurum, 1998). "All extant mammals" includes monotremes, such as the duck-billed platypus, despite its residual egg-laying habit.