I recently saw this carnivorous mammal tooth from the Brule Formation for sale. It is labelled as being that of a Hesperocyon gregarius, but what little I know of carnivorous mammal dentition leads me to believe that the tooth could in fact come from a Hyaenodon. As always, I've decided I'm going to play it safe and ask someone of greater expertise to verify this. It is my understanding that @jpc, @Randyw and @ParkerPaleo are all Brule Formation specialists, so I will take the liberty of "@ing" you all in.
Thanks in advance for any guidance
Othniel