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Temporal range: Middle Eocene
Holotype skull of Andrewsarchus mongoliensis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Clade: Cetancodontamorpha
Family: Andrewsarchidae
Szalay & Gould, 1966[2]
Genus: Andrewsarchus
Osborn, 1924[1]
Type species
Andrewsarchus mongoliensis
Osborn, 1924
Other species
  • Andrewsarchus crassum
    Ding, Zheng, Zhang, & Tong, 1977[3]
Genus synonymy
Species synonymy
  • A. mongoliensis
      • Paratriisodon henanensis
        Chow, 1959
      • Paratriisodon gigas
        Chow, Li, & Chang, 1973[5]

Andrewsarchus (/ˌændrˈsɑːrkəs/) is an extinct genus of ungulate that lived during the Middle Eocene in China. It contains two species, A. mongoliensis and A. crassum. It was formerly placed in the families Mesonychidae or Arctocyonidae, but is now the sole member of a distinct family, Andrewsarchidae. Only known from a largely complete skull as well as isolated teeth, it is notable for being estimated as the largest terrestrial, carnivorous mammal, but that status has been disputed.


Andrewsarchus mongoliensis was named by Henry Fairfield Osborn in 1924 for a partial skull from the Irdin Manha Formation of Inner Mongolia. The genus was named in honor of Roy Chapman Andrews, the leader of the expedition on which it was discovered, with the Ancient Greek archos (ἀρχός, "ruler") added to his surname.[1] A second species, A. crassum, was named by Ding Suyin and colleagues in 1977 for two premolars from the Dongjun Formation of Guangxi,[3] but its specimens are too fragmentary to establish broader affinities of the genus.[6]

Paratriisodon henanensis was named by Minchen Chow in 1959 for a partial skull and mandible, a fragmentary maxilla, and several isolated teeth from the Lushi Formation of Henan.[4] A second species, P. gigas, was named by Chow and colleagues in 1973 for a molar also from the Lushi Formation.[5] Three molars and an incisor from the Irdin Manha Formation were later referred to P. gigas.[7] Both species are considered junior synonyms of A. mongoliensis.[6]

Andrewsarchus is the only member of the family Andrewsarchidae, which was named by Frederick Szalay and Stephen Jay Gould in 1966. It was originally named as a subfamily of Mesonychidae,[2] but was later raised to the rank of family.[8]


Life restoration

Andrewsarchus was originally classified as a member of the family Mesonychidae[2][1][3] and Paratriisodon was originally classified as a member of the family Arctocyonidae.[4][5][7] Andrewsarchus was then reassigned to its own family Andrewsarchidae, but retained within the order Mesonychia.[8] After that, Paratriisodon was synonymized with Andrewsarchus and the latter was moved to Arctocyonidae.[6] More recently, it has been recovered as a member of the clade Cetancodontamorpha, being most closely related to entelodonts, hippos, and whales.[9][10]

Below is a simplified cladogram based on the results of Spaulding et al. (2009) and Yu et al. (2023).[9][10]



Skull compared to those of Mesonyx, an Alaskan brown bear, and a wolf

When first describing Andrewsarchus, Osborn believed it to be the largest terrestrial, carnivorous mammal. Based on the 83.4 cm (2.74 ft) length of the A. mongoliensis holotype skull, and using the proportions of Mesonyx, he estimated a total body length of 3.82 m (12.5 ft) and body height of 1.89 m (6.2 ft).[1] However, considering cranial and dental similarities with entelodonts, Szalay and Gould proposed that it had proportions more like them than mesonychids and that Osborn's estimates were inaccurate. They also suggested that it was likely an omnivore.[2] These ideas are also supported by the close phylogenetic relationship between Andrewsarchus and entelodonts.[9][10]

See also[edit]


  1. ^ a b c d Osborn, H.F. (1924). "Andrewsarchus, giant mesonychid of Mongolia". American Museum Novitates (146): 1–5. hdl:2246/3226.
  2. ^ a b c d Szalay, F.S.; Gould, S.J. (1966). "Asiatic Mesonychidae (Mammalia, Condylartha)". Bulletin of the American Museum of Natural History. 132 (2): 127–174. hdl:2246/1112.
  3. ^ a b c Ding, S.; Zheng, J.; Zhang, Y.; Tong, Y. (1977). "The age and characteristic of the Liuniu and the Dongjun faunas, Bose Basin of Guangxi" (PDF). Vertebrata PalAsiatica. 15 (1): 35–45.
  4. ^ a b c Chow, M.M. (1959). "A new arctocyonid from the Upper Eocene of Lushih, Honan" (PDF). Vertebrata PalAsiatica. 3 (3): 133–138.
  5. ^ a b c Chow, M.M.; Li, C.; Chang, Y. (1973). "Late Eocene mammalian faunas of Honan and Shansi with notes on some vertebrate fossils collected therefrom" (PDF). Vertebrata PalAsiatica. 11 (2): 165–181.
  6. ^ a b c O'Leary, M.A. (1998). "Phylogenetic and Morphometric Reassessment of the Dental Evidence for a Mesonychian and Cetacean Clade". In Thewissen, J.G.M. (ed.). The Emergence of Whales. Springer. pp. 133–161. doi:10.1007/978-1-4899-0159-0_5. ISBN 978-1-4899-0159-0.
  7. ^ a b Qi, T. (1980). "Irdin Manha Upper Eocene and its mammalian fauna at Huhebolhe Cliff in central Inner Mongolia" (PDF). Vertebrata PalAsiatica. 18 (1): 28–32.
  8. ^ a b Zhou, X. (1995). Evolution of Paleocene-Eocene Mesonychidae (Mammalia, Mesonychia) (PhD dissertation). University of Michigan. hdl:2027.42/129581.
  9. ^ a b c Spaulding, M.; O'Leary, M.A.; Gatesy, J. (2009). "Relationships of Cetacea (Artiodactyla) among mammals: Increased taxon sampling alters interpretations of key fossils and character evolution". PLOS ONE. 4 (9): e7062. Bibcode:2009PLoSO...4.7062S. doi:10.1371/journal.pone.0007062. PMC 2740860. PMID 19774069.
  10. ^ a b c Yu, Y.; Gao, H.; Li, Q.; Ni, X. (2023). "A new entelodont (Artiodactyla, Mammalia) from the late Eocene of China and its phylogenetic implications". Journal of Systematic Palaeontology. 21 (1): 2189436. Bibcode:2023JSPal..2189436Y. doi:10.1080/14772019.2023.2189436. S2CID 257895430.