Name Meaning: Ancient Beast
Location Found: White River Formation. South Dakota
Geologic Era: Late Eocene to Early Oligocene
Size: 1.5 meters tall
Estimated Range: Northern North America and Southern Canada
Extinction Date: 24.8 million years ago
This is a tooth and partial jaw from a pig-like entelodont. Just the size of the single tooth and jaw fragment suggest a large animal. While superficially resembling a pig in appearance, these animals are actually more closely related to the hippopotamus. Archaeotherium was a sizable animal by itself, though it was outclassed in that regard by Eurasian entelodonts such as Entelodon.
Entelodonts had a very large geographical distribution, being found in North America and Eurasia. In terms of diet, they may have been like the modern pigs they resemble and were omnivorous. Their grinding surfaces of their molars make it clear that they could process plant material, though the canine and incisor teeth look more like something one would expect on a carnivore. Archaeotherium could also open its jaws very wide, much wider than what would be expected from a simple herbivore. This ability to make the mouth more intimidating in appearance could be linked to intraspecific display (between members of the same species) or intraspecific (other species).
Archaeotherium would have been larger than most if not all of the predators in its environment, so it could have easily forced a smaller predator away from a kill. In terms of energy conservation, this strategy makes a lot of sense. Archaeotherium would let the other predator do the hard work, then just steal the spoils. This does not mean that Archaeotherium was unable to take down prey itself. Its jaw structure indicates a fairly strong bite, more than enough to kill prey by itself. Early camel remains (Poebrotherium) have been found in what appear to be a food cache made by an Archaeotherium. This by itself may indicate a prey preference for these early camels, as well as oreodonts. Both of these animals were smaller and more lightly built than Archaeotherium, and would have been relatively easy targets.
espite its intimidating appearance, Archaeotherium was probably not terribly intelligent, and was not likely to be able to plan or carry out complex behavior. It was, however, more than capable of tracking live or dead prey items. Tracks attributed to Archaeotherium (or an animal very similar to it) have been located that appear to show the animal moving in a zigzag pattern. While an inefficient method of movement, this pattern is very good for picking up scents from different directions.
Coincidentally, this set of tracks appears to follow those made by a creodont such as Hyaenodon and an ancient rhinoceros. Why the tracks seem to parallel each other is up for debate. The Archaeotherium could have been tracking the other two, perhaps with intent to steal a rhinoceros kill from the creodont. Or, the two paths are coincidental and were not made at the same time. Either way, this track set indicates that animals very different from those we see today roamed North America in the past.
Full Skeleton: By Ryan Somma – Archaeotherium mortoni, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=4984296
Life Reconstruction: http://spinops.blogspot.com/2012/01/archaeotherium-mortoni.html