Andrewsarchus
Extinct artiodactyl known from a large skull found in China.
Wikipedia / Wikimedia Commons
Andrewsarchus—whose name honors explorer Roy Chapman Andrews, with the Greek word for "ruler" tacked on—is an extinct genus of artiodactyl from the Middle Eocene of China. Henry Fairfield Osborn first described it in 1924, basing the type species *A. mongoliensis* on a nearly complete skull. A second species, *A. crassum*, was added in 1977 from a pair of teeth. A jawbone once called *Paratriisodon* probably also belongs here. Over the years, scientists have lumped *Andrewsarchus* into the families Mesonychidae or Arctocyonidae, or considered it a close whale relative. Today it stands alone in its own family, Andrewsarchidae, with possible ties to entelodonts. Its fossils come from three Middle Eocene formations in Inner Mongolia—the Irdin Manha, Lushi, and Dongjun—dating to between 48 and 38 million years ago.
For a long time, *Andrewsarchus* was famous as the biggest land-dwelling meat-eating mammal, thanks to a skull 83.4 centimeters long. But that reputation probably inflated its true body size, because early comparisons leaned on mesonychids rather than the more appropriate entelodonts. Its teeth tell a different story: no meat-slicing carnassials, incisors arranged in a semicircle (like entelodonts), premolars with a single cusp, and wrinkled molar crowns—all signs it was omnivorous or a scavenger. A reduced sagittal crest and flat mandibular fossa suggest its bite was fairly weak, unlike many modern scavengers.
The holotype skull (AMNH-VP 20135) was dug up in 1923 from the lower Irdin Manha Formation during an American Museum of Natural History expedition. The finder was Kan Chuen-pao, a local man trained at the museum, who worked as assistant to paleontologist Walter Granger. Granger first thought it was an *Entelodon* skull. A drawing sent to the museum led William Diller Matthew to peg it as a mesonychid creodont. Osborn published the formal description in 1924. The second species, *A. crassum*, rests on two lower premolars from Guangxi’s Dongjun Formation, named by Ding Suyin and colleagues in 1977.
In 1957, Zhou Mingzhen and his team recovered a mandible, a fragmentary maxilla, and isolated teeth from Henan’s Lushi Formation. The maxilla came from a crushed skull, likely the same individual as the jaw. Zhou described it in 1959 as *Paratriisodon henanensis*, placing it in Arctocyonidae and subfamily Triisodontinae, based on molar and premolar
- lived
- Middle Eocene (Lutetian–Bartonian stages, 48–38 million years ago)
- discovered
- 1923, Inner Mongolia
- named_by
- Henry Fairfield Osborn, 1924
- type_species
- Andrewsarchus mongoliensis
- family
- Andrewsarchidae
- known_for
- Large skull (83.4 cm), historically considered largest terrestrial carnivorous mammal
Lore & Background
The holotype of Andrewsarchus mongoliensis is a mostly complete cranium recovered from the lower Irdin Manha Formation of Inner Mongolia during a 1923 palaeontological expedition by the American Museum of Natural History. Its discoverer was Kan Chuen-pao, a local man who trained at the AMNH. The specimen was initially identified as an Entelodon by Walter Granger, then as a mesonychid by William Diller Matthew, and finally described by Osborn in 1924. The generic name honors expedition leader Roy Chapman Andrews, with the Ancient Greek 'archos' (ruler) added to his surname.
A second species, A. crassum, was named in 1977 based on a pair of teeth from the Dongjun Formation of Guangxi. A mandible and teeth previously described as Paratriisodon henanensis and P. gigas from the Lushi Formation were later synonymized with Andrewsarchus by Leigh Van Valen in 1978, a synonymy upheld by Maureen O'Leary in 1998 based on dental similarities and comparable body sizes.
Andrewsarchus has been classified variously in Mesonychidae, Arctocyonidae, or as a close relative of whales. It is now placed in its own family, Andrewsarchidae, and phylogenetic analysis in 2023 recovered it in a clade with Achaenodon, Erlianhyus, and entelodonts. Its fossils have been found in the Irdin Manha, Lushi, and Dongjun Formations, all dated to the Irdinmanhan Asian land mammal age.
Reader's Guide
Andrewsarchus is significant primarily for its historical reputation as the largest terrestrial carnivorous mammal, based on its 83.4 cm skull. However, this reputation has been revised: its overall body size was probably overestimated due to inaccurate comparisons with mesonychids, and it lacked the meat-slicing carnassial teeth of a hypercarnivore. Its dentition—including incisors arranged in a semicircle, premolars with a single cusp, and wrinkled molar crowns—suggests it was omnivorous or a scavenger. A reduced sagittal crest and flat mandibular fossa indicate a fairly weak bite force, unlike many modern scavengers.
Its classification has shifted dramatically over a century, from mesonychid to arctocyonid to relative of whales, and finally to its own family within Cetancodontamorpha, most closely related to entelodonts. This taxonomic journey reflects broader changes in mammalian paleontology. The synonymy of Paratriisodon with Andrewsarchus expanded the known material beyond the holotype skull, though much of its biology remains uncertain. The genus remains a key example of how early estimates of extinct animal size and ecology can be misleading, and how new phylogenetic analyses can overturn long-held assumptions.
Did You Know?
- The holotype skull of Andrewsarchus mongoliensis is 83.4 cm long and 56 cm wide at the zygomatic arches.
- Its discoverer was Kan Chuen-pao, a local man who trained at the American Museum of Natural History and was known as 'Buckshot'.
- The second incisor of Andrewsarchus is enlarged and almost the size of the canine.
- A mandible formerly described as Paratriisodon henanensis probably belongs to Andrewsarchus.
Frequently Asked Questions
What is Andrewsarchus?
Andrewsarchus is an extinct even-toed ungulate (artiodactyl) that roamed what is now China during the Middle Eocene. Its name honors explorer Roy Chapman Andrews and appends the Greek word for 'ruler.'
Who discovered and named Andrewsarchus?
Fossils were pulled from Inner Mongolia in 1923, and paleontologist Henry Fairfield Osborn formally described the type species A. mongoliensis in 1924 using a nearly complete skull.
How big was Andrewsarchus?
The best-known skull measures roughly 83.4 centimeters, a size that once led researchers to label it the largest land-based carnivorous mammal of its time.
What family does Andrewsarchus belong to?
Its taxonomic home has bounced between Mesonychidae, Arctocyonidae, and even a close whale lineage over the decades, but it is now placed in its own family, Andrewsarchidae.
How many species of Andrewsarchus are recognized?
Two species are currently accepted: the type A. mongoliensis and A. crassum, the latter added in 1977 from just a pair of teeth. A jawbone long called Paratriisodon is also probably part of this genus.
More in Extinct Cenozoic Mammals 1-24
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