Olson concluded that AM 4471 was too poorly preserved to differentiate from D. magnicornis, and therefore he designated D. limbatus as a synonym of that species. However, he also analyzed the referred D. limbatus skull described by Case, AM 4470, and found that it was unique enough to qualify as the type specimen of a new Diplocaulus species: D. brevirostris.
The researcher Olson determined that AM 4471 was too worn out to be distinguished from D. magnicornis, so he designated D. limbatus as an equivalent name for that species. Nonetheless, he also analyzed the skull referred to as D. limbatus (AM 4470) described by Case and found it unique enough to qualify as the type specimen for a new Diplocaulus species: D. brevirostris.