Gallimimus (gal-IH-mime-US) was a fast, ostirich-like dinosaur, with a long, extended tail for balancing while running, and was rather intelligent by dinosaur standards. It had a long neck and large, round eyes, possibly for night vision, suggesting a nocturnal lifestyle (though there is no reason it wasn't diurnal).
Gallimimus was found in the Gobi Desert in Mongolia in early 1963 by Professor Zofia Kielan-Jaworowska. It was named by palaeontologist Richen Barsbold in 1972, who thought it looked rather rooster-like in appearance. Most fossils have been found in Mongolia. At the time only one species of Gallimimus was known, and it was dubbed Gallimimus bullatus, because of the bulbous swelling in the brain-case resembled a bulla; a capsule which was worn by Roman youths around their necks. A second species, named Gallimimus mongoliensis, was discovered in 1996.
Gallimimus was briefly shown in Jurassic Park as a stampeding herd that ran at the protagonists, and one was then attacked and eaten by a Tyrannosaurus rex. However, in real life, it would probably have been eaten by the T. rex's close relative Tarbosaurus for Gallimimus was an Asian dinosaur, which didn't live in North America unlike Tyrannosaurus rex.
Also, in the Carnivores series, they appear as ambient creatures that run away if the player is to close. They also made a few appearances in The Land Before Time film series. They are also a playable dinosaur in the game Dinosaur King.
It is likely that Gallimimus was a very intelligent creature, based on mass and the proportion to the brain, meaning that they were probably quite smart among most dinosaurs. It shared many features with its relatives. such as Ornithomimus. It is guessed that Gallimimus was an omnivore, similiar to the Oviraptor. Its main diet consisted of small lizards and bugs, some eggs, and some plants. Gallimimus ran on two slender legs. It's predicted to have been ostrich-like, and most likely had feathers, given that feathers were preserved in it's relatives and more massive feathered dinosaurs did exist. It had a long, flat, toothless beak, with the lower jaw being shaped like a shovel, a tool which would have probably been helpful in crunching hard materials like nuts or roots. It weighed about 970 lbs and was about 8 meters (26 feet) in length, making it one of the largest of ornithomimids. It had three claws on each arm, with three on each foot. The tail, like many other dinosaurs, was meant for balance, especially while they were running. Like other ornithomimids, it was a very fast runner, possibly capable of running up to 43 mph, which is about the same as an ostirich's top speed and over twice as fast as Olympic sprinters! Gallimimus also had large eyes, which possibly suggests that they were nocturnal dinosaurs like the Troodon.