Andrewsarchus, "Superb Skull of a Gigantic Beast"

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In the spring of 1923, a group of Museum researchers who had recently embarked on the second year of the Central Asiatic Expeditions made camp at Irdin Manha—the Valley of the Jewels—in Inner Mongolia. Named for the brilliantly polished pebbles of agate, chalcedony, jasper, quartz, and other minerals found there, Irdin Manha immediately proved a rich trove of fossil “jewels” as well.

A day or two after the team’s arrival, Kan Chuen Pao (pictured below), a young paleontological assistant, made an amazing find: “the superb skull of a gigantic beast,” as described by the expedition’s leader Roy Chapman Andrews, who would later become the Museum’s director. At nearly 3 feet long, the skull was massive, and its teeth were huge.

Kan Chuen Pao (Andrewsarchus)
Kan Chuen Pao stands in the second row, at second from left. Pao discovered the skull of Andrewsarchus in 1923 in Mongolia. Lead paleontologist Walter Granger sits in the front row, left.
The New Conquest of Central Asia, by Roy Chapman Andrews

Andrews decided the animal was a carnivore. But there was disagreement in the camp. The lead paleontologist, Walter Granger, thought that the skull belonged to a member of an extinct group of pigs, which were omnivorous. Another expedition member drew the skull and jaw and forwarded the illustration to the Museum for further study. The specimen soon followed, becoming part of the collection later that year. 

It was given the name Andrewsarchus mongoliensis, in honor of the expedition’s leader, and remains the only specimen ever found of the species, which lived about 45 million years ago.

Andrewsarchus skull
Andrewsarchus mongoliensis
© AMNH/R. Mickens

Although only the skull of Andrewsarchus mongoliensis has ever been found, researchers infer from the fossil’s size and evolutionary relationships that the animal was about 6 feet high at the shoulder and 12 feet long, a size that would make Andrewsarchus the largest known meat-eating land mammal that ever lived.

© Mick Ellison

At the time, Museum researchers dubbed Andrewsarchus “the giant mesonychid of Mongolia,” classifying it as a member of an extinct group of hoofed carnivores called mesonychids. Later on, mesonychids were thought to be closely related to whales. But while it turns out that Andrewsarchus isn’t a mesonychid, recent evolutionary analysis suggests it is a whale cousin after all.

In fact, Andrewsarchus is closely related to hippos and to whales, both members of a larger order of mammals called artiodactyls. This group of two-toed hoofed mammals also includes sheep, pigs, cows, deer, giraffes, and antelopes. Today, hippos are the largest land artiodactyls, and cetaceans—whales, dolphins, and porpoises—are the only aquatic artiodactyls.

A version of this story appears in the summer 2013 issue of Rotunda, the Member magazine.

See a cast of the Andrewsarchus skull on the Museum's fourth floor, in the Milstein Hall of Advanced Mammals.