Gastornis was a specialized herbivore (or even an omnivore) of some sort, perhaps having used its large beak to crack hard foods like nuts and seeds. Footprints attributed to gastornithids (possibly a species of Gastornis itself), described in 2012, showed that these birds lacked strongly hooked talons on the hind legs, another line of evidence suggesting that they did not have a predatory lifestyle. Recent evidence suggests that Gastornis was likely a true herbivore. Studies of the calcium isotopes in the bones of specimens of Gastornis by Thomas Tutken and colleagues showed no evidence that it had meat in its diet. The geochemical analysis further revealed that its dietary habits were similar to those of both herbivorous dinosaurs and mammals when it was compared to known fossil carnivores, such as Tyrannosaurus rex, leaving phorusrhacids as the only major carnivorous flightless birds. Eggs In Late Paleocene deposits of Spain and early Eocene deposits of France, shell fragments of huge eggs have turned up, namely in Provence. These were described as the ootaxon Ornitholithus and are presumably from Gastornis. While no direct association exists between Ornitholithus and Gastornis fossils, no other birds of sufficient size are known from that time and place; while the large Diogenornis and Eremopezus are known from the Eocene, the former lived in South America (still separated from North America by the Tethys Ocean then) and the latter is only known from the Late Eocene of North Africa, which also was separated by an (albeit less wide) stretch of the Tethys Ocean from Europe. Some of these fragments were complete enough to reconstruct a size of 24 by 10 cm (about 9.5 by 4 inches) with shells 2.3–2.5 mm (0.09–0.1 in) thick, roughly half again as large as an ostrich egg and very different in shape from the more rounded ratite eggs. If Remiornis is indeed correctly identified as a ratite (which is quite doubtful, however), Gastornis remains as the only known animal that could have laid these eggs. At least one species of Remiornis is known to have been smaller than Gastornis, and was initially described as Gastornis minor by Mlíkovský in 2002. This would nicely match the remains of eggs a bit smaller than those of the living ostrich, which have also been found in Paleogene deposits of Provence, were it not for the fact that these eggshell fossils also date from the Eocene, but no