Gastornis is an extinct genus of large flightless bird that lived during the late Paleocene and Eocene epochs of the Cenozoic. It was named in 1855, after Gaston Planté, who had discovered the first fossils in Argile Plastique formation deposits at Meudon near Paris (France). At that time, Planté (described as a "studious young man full of zeal") was at the start of his academic career, and his remarkable discovery was soon to be overshadowed by his subsequent achievements in physics.
In the 1870s, the famous American paleontologist Edward Drinker Cope discovered another, more complete set of fossils in North America, and named them Diatryma (from Ancient Greek διάτρημα, diatrema, meaning "canoe").
Description
Gastornis parisiensis measured on average 1.75 metres (5.7 ft) tall, but large individuals grew up to 2 metres (6.6 ft) tall. The Gastornis had a remarkably huge beak with a slightly hooked top, which was taken as evidence suggesting that it was carnivorous. Gastornis had large powerful legs, with large, taloned feet, which also were considered in support of the theory that it was a predator.
The plumage of Gastornis is unknown; it is generally depicted with a hair-like covering as in ratites, but this is conjectural. Some fibrous strands recovered from a Green River Formation deposit at Roan Creek, Colorado were initially believed to represent Gastornis feathers and named Diatryma filifera. Subsequent examination showed that they were actually not feathers at all but plant fibers or similar.
Paleoecology
At its time, the environment in which Gastornis lived had large portions of dense forest and a moist semiarid, subtropical or tropical climate. North America and Europe were still rather close, and especially since Greenland was probably then covered with lush woodland and grassland, only narrow straits of a few 100 km would have blocked entirely landbound dispersal of the Gastornis ancestors. While there were large contiguous areas of land in their North American range after the Western Interior Seaway had receded, their European range was an archipelago due to the Alpide orogeny and the high sea levels of the Paleocene-Eocene Thermal Maximum; geographically (but not geologically), it was perhaps roughly similar to today's Indonesia.
Classically, Gastornis has been depicted as predatory. However, with the size of Gastornis legs, the bird would have had to have been more agile to catch fast-moving prey than the fossils suggest it to have been. Consequently, it has been suspected that Gastornis was an ambush hunter and/or used pack hunting techniques to pursue or ambush prey; if Gastornis was a predator, it would have certainly needed some other means of hunting prey through the dense forest.
Alternatively, they may have been predominantly scavengers, omnivores or even herbivores. Indeed, the large beak of Gastornis would have been as well suited for crushing seeds and tearing off vegetation. But it seems excessively strong for a purely vegetarian diet, except in the rather improbable case that huge hard-shelled seeds and nuts formed the main food item of Gastornis. Regardless of what these birds ate, the beak may simply have been used for social display though its presence in all known fossils argues against a sexual display role. These contradicting hypotheses, equivocally supported by the material evidence, make the dietary paleobiology of Gastornis impossible to pinpoint.
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