Premise: Arctocyon ('bear dog') is an extinct genus of ungulate mammals. "Arctocyon" was a "ground dwelling omnivore", that lived from 61.3-56.8 Ma. Synonyms of "Arctocyon" include "Claenodon", and "Neoclaenodon". "Arctocyon" was likely plantigrade, that is, walked like a bear.
Hypothesis: Arctocyon was alive from 61.3-52.8 Ma.