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Description

A prehistoric beast that’s both famous but also very enigmatic. Andrewsarchus mongoliensis is a large meat-eating ungulate from the Mid Eocene, whose holotype was famously discovered during the AMNH-funded fossil expeditions in Central Asia during the early 20th century, led by the real-life Indiana Jones inspiration Roy Chapman Andrews, after whom the beast is named (its generic name meaning “Andrew’s ruler”). It’s only known from a single huge skull, stretching 83 cm in length, which stems from the Irdin Manha Formation of Inner Mongolia (45-40 mya). Though its describer, Henry Fairfield Osborn originally identified it as a colossal mesonychid, others at the time noted similarities between its skull and that of entelodonts, and sure enough, 21st-century studies recover Andrewsarchus as a cetancodontamorph, a group whose only living representatives are whales and hippos, and it also includes entelodonts, which some consider to be the closest relatives of Andrewsarchus.

However, no study has placed Andrewsarchus in any specific family of cetancodontamorphs, making it hard to try and phylogenetic bracket how the rest of its body would have looked like, with most reconstructions these days showing it as either an entelodont redux or as a kind of hippo-entelodont with a long tail. Though based on its family heritage, it’s very likely that Andrewsarchus at least had an oversized head, much like other cetancodontamorphs from the Eocene; such as entelodonts, basal cetaceans like Ambulocetus and Pakicetus, and anthracotheres (stem-hippos), and the holotype skull is only slightly smaller than those of the largest entelodonts (who stretch a full 90 cm), so this would likely have been a cow-sized mammal (in terms of possible size range).

Because we lack any postcranial remains, we can only guess how A. mongoliensis might have lived, though like the later entelodonts, or extant bears, it might have been a generalist who used its sheer size and bulk to steal the kills of smaller sympatric predators like Sarkastodon and Mongolonyx, infrequently having to hunt its own prey because of it.

Description

A prehistoric beast that’s both famous but also very enigmatic. Andrewsarchus mongoliensis is a large meat-eating ungulate from the Mid Eocene, whose holotype was famously discovered during the AMNH-funded fossil expeditions in Central Asia during the early 20th century, led by the real-life Indiana Jones inspiration Roy Chapman Andrews, after whom the beast is named (its generic name meaning “Andrew’s ruler”). It’s only known from a single huge skull, stretching 83 cm in length, which stems from the Irdin Manha Formation of Inner Mongolia (45-40 mya). Though its describer, Henry Fairfield Osborn originally identified it as a colossal mesonychid, others at the time noted similarities between its skull and that of entelodonts, and sure enough, 21st-century studies recover Andrewsarchus as a cetancodontamorph, a group whose only living representatives are whales and hippos, and it also includes entelodonts, which some consider to be the closest relatives of Andrewsarchus.

However, no study has placed Andrewsarchus in any specific family of cetancodontamorphs, making it hard to try and phylogenetic bracket how the rest of its body would have looked like, with most reconstructions these days showing it as either an entelodont redux or as a kind of hippo-entelodont with a long tail. Though based on its family heritage, it’s very likely that Andrewsarchus at least had an oversized head, much like other cetancodontamorphs from the Eocene; such as entelodonts, basal cetaceans like Ambulocetus and Pakicetus, and anthracotheres (stem-hippos), and the holotype skull is only slightly smaller than those of the largest entelodonts (who stretch a full 90 cm), so this would likely have been a cow-sized mammal (in terms of possible size range).

Because we lack any postcranial remains, we can only guess how A. mongoliensis might have lived, though like the later entelodonts, or extant bears, it might have been a generalist who used its sheer size and bulk to steal the kills of smaller sympatric predators like Sarkastodon and Mongolonyx, infrequently having to hunt its own prey because of it.