Deinocheirus modernus is an unusual ornithomimosaur, the largest of the clade at 11 m (36 ft) long, and weighing 6.4 t (7.1 short tons). Though it is a bulky animal, it has many hollow bones which saves weight. The arms are among the largest of any bipedal dinosaur at 2.4 m (7.9 ft) long, with large, blunt claws on its three-fingered hands. The legs are relatively short, and has blunt claws. Its vertebrae has tall neural spines that forms a "hump" along its back. Most of the vertebrae and some other bones are highly pneumatised by invading air sacs. The tail ends in pygostyle-like vertebrae, which forms a fan of feathers. The skull is 1.024 m (3.36 ft) long, with a wide bill and a deep lower jaw, similar to those of hadrosaurs. Deinocheirus modernus is omnivorous, mainly feed on plants and fish, it swallows gastroliths (stones) in order to grind up plant matter. The large claws are used for digging up plant matter and gathering plants, but can also be used to catch fish and for defense against predators. During mating seasons, the males fight over other males, using claws for fighting, until one backs down, and the winner gets a right to mate. The females can lay around 40-45 eggs about 2-3 months after mating seasons, the eggs hatch around 1-2 months after being laid, and the hatchlings are cared for by their mothers until they are fully-grown, when they must fend for themselves.