“A” is for Acmeodon.
Acmeodon was an insectivorous mammal in the Order Cimolesta.
Acmeodon secans is known from two localities in The Breaks, both of which are early Tiffanian (overlap zone) in age. It is known more broadly from late Torrejonian into early Tiffanian faunas.
These are all upper molars. Read more about mammal molars here.
Part of the Blogging from A to Z challenge.