Comparison of the artiodactyls Entelodon deguilhemi and Bachitherium insigne from the early Oligocene of France.
Deguilhem's Entelodon (at top), Entelodon deguilhemi, was a cow-sized omnivore related to modern-day pigs, much in the same manner rhinoceroses are related to tapirs. Many people mention how the entelodonts were the apex predators of the Oligocene and Miocene, though, it's unlikely that most, except possibly Daeodon, caught their prey. Instead, it is presumed that most entelodonts satisfied their carnivory by scavenging and usurping the kills of other predators.
Bachitherium insigne is one of the best known early ruminants from the Paleogene, primarily because complete skeletons have been found. In life, it would have looked something like a camel-faced gazelle-goat, without horns.