Andrewsarchus (/ˌændruːˈsɑːrkəs/) is an extinct genus of mammal 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. It is most 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]
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.[6] Both species are considered junior synonyms of A. mongoliensis.[7]
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]
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][6] 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.[7] 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]