Microceratus (known as "Microceratops" before 2008) is a genus of very small, bipedal ceratopsian dinosaurs. They lived in China and Mongolia during the Late Cretaceous period, around 90 million years ago.
Microceratus in The Land Before Time
A Microceratus, referred to as the Great Hideous Beast by the characters, terrorizes a Ceratogaulus burrow in "Stranger from the Mysterious Above" for the sake of exploiting their food supply. Spike ends up frightening it away, saving the mammals.