Gastornis (Diatryma)

Diatryma steini

Ryan Somma 


Gastornis (Greek for "Gaston's bird"); pronounced gas-TORE-niss; also known as Diatryma


Woodlands of Western Europe, North America, and eastern Asia

Historical Epoch:

Late Paleocene-Middle Eocene (55-45 million years ago)

Size and Weight:

About six feet tall and a few hundred pounds


Unknown; probably herbivorous

Distinguishing Characteristics:

Short, powerful legs and beak; squat trunk

About Gastornis

First things first: the flightless prehistoric bird we now know as Gastornis used to be called Diatryma (Greek for "through a hole"), the name by which it was recognized by generations of schoolchildren. After examining some fossil specimens unearthed in New Mexico, the famous American paleontologist Edward Drinker Cope coined the name Diatryma in 1876, not knowing that a more obscure fossil hunter, Gaston Plante, had bestowed his own name on this genus a couple of decades earlier, in 1855, based on a set of bones discovered near Paris. With true scientific evenhandedness, the name of this bird gradually reverted back to Gastornis in the 1980s, generating almost as much confusion as the roughly contemporary switch from Brontosaurus to Apatosaurus.

Naming conventions aside, at six feet tall and a few hundred pounds Gastornis was far from the biggest prehistoric bird that ever lived--that honor belongs to the half-ton Aepyornis, the Elephant Bird--but it may have been one of the most dangerous, with a tyrannosaur-like profile (powerful legs and head, puny arms) that demonstrates how evolution tends to fit the same body shapes into the same ecological niches. (Gastornis first popped up in the northern hemisphere about 10 million years after the dinosaurs went extinct, during the late Paleocene and early Eocene epochs). Even worse, if Gastornis was capable of pack hunting, one imagines that it could depopulate an ecosystem of small animals in no time flat!

There's a major problem with this pack-hunting scenario, however: lately, the weight of the evidence is that Gastornis was a herbivore rather than a carnivore. Whereas early illustrations of this bird depicted it munching on Hyracotherium (the tiny prehistoric horse previously known as Eohippus), a chemical analysis of its bones points to a plant-eating diet, and its massive skull has been reinterpreted as ideal for crunching tough vegetation rather than flesh. Tellingly, Gastornis also lacked the hooked beak characteristic of later meat-eating birds, such as Phorusrhacos, aka the Terror Bird, and its short, stubby legs would have been little use chasing prey through the rough underbrush of its environment.

Aside from its numerous fossils, Gastornis is one of the few prehistoric birds to be associated with what appear to be its own eggs: shell fragments recovered from western Europe have been reconstructed as oblong, rather than round or ovoid, eggs measuring nearly 10 inches long and four inches in diameter. The putative footprints of Gastornis have also been discovered in France and in Washington state, and a pair of what are believed to be Gastornis feathers have been recovered from the Green River fossil formation in the western U.S. As prehistoric birds go, Gastornis clearly had an unusually widespread distribution, a clear indication (no matter the details of its diet) that it was well-adapted to its place and time.

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Strauss, Bob. "Gastornis (Diatryma)." ThoughtCo, Feb. 16, 2021, Strauss, Bob. (2021, February 16). Gastornis (Diatryma). Retrieved from Strauss, Bob. "Gastornis (Diatryma)." ThoughtCo. (accessed March 31, 2023).