Ostrich Like in appearance, Gallimimus (Chicken Mimic) is among the largest herbivore theropods. It is considered an herbivore despite occasionally seeking and eating mollusks and crustaceans from water sources on the island (often during mating season).

Like modern birds, Gallimimus has very lightweight bones and due to the flock-running natural habits of the species they are sometimes quite lean despite regular feeding stops. This leads to a proportionately lightweight and therefore fast running dinosaur. Despite their relatively small head and claw, and lack of binocular vision (their large eyes are on the sides of their head instead of nearer the front), and the fact that they possess no teeth in their beaked mouth, their speed and size still make them dangerous to be around without protection. It is recommended that shelter be found immediately if a gallimumus flock is in the area.

Like chickens, the beak of a gallimimus is rather small when first hatched, but grows longer and more pronounced with age.

The first successful specimen of gallimimus was g. Nublariensis and was among the first species developed by the International Genetics Corporation for their Jurassic Park project in the late 1980s. SCGC developed g. Timothi from a series of samples collected at the same dig site with a far more accurate genetic code to the paleotype g. Bullatus including the presence of feather growth.