I love a good story about science marching forward, and this story contains a great story about not making assumptions before having a larger pool of data. In 1965, a pair of 8 foot long forearms, each tipped with three massive claws was discovered in the Ömnögovi Province in Mongolia. They were believed to belong to a large carnivore, and classed the animal in the Megalosauridae family of super predators.
However, thanks to the recent discoveries of two complete skeletons, Yuong-Nam Lee, from South Korea's Institute of Geoscience and Mineral Resources (Kigam) and co-published by the University of Alberta, has been able to describe the complete animal, and it's a weird one. Deinocheirus mirificus (which means "unusual, horrible hands") was 36 feet long and weighed six tonnes, and looked like the sort of dinosaurs a three year old would draw with a crayon. Now officially classed as a ornithomimosaur theropod, whose diet consisted of slashed undergrowth - hence the claws - and fish, based on bones found in the fossils of the animals, the animal possessed the gait of a hadrosaur, the body of an obese hunchback, and the face of a Muppet.