Gallimimus is a dinosaur that lived a long time ago. It was very big and had a long neck and a long tail. It looked a bit like an ostrich. Gallimimus used to walk on two legs and had big strong legs to run really fast. Just like today’s birds, Gallimimus laid eggs and built nests to keep their eggs safe. They ate plants and small animals. Even though they were big, they were not mean or scary. Gallimimus is now extinct, which means there are no more of them around.