Nanotankylosaurus

Nanotankylosaurus was a species of Ankylosaurid and the last of their kind. They lived during the Late Cretaceous about 85 million years ago to the Late Pleistocene about 10,000 years ago, so they were one of the oldest land vertebrates on Earth. During the Cretaceous, they were about the size of Ankylosaurus (their neighbors) and were preyed on by raptor dinosaurs and T-Rex, due to the mass extinction that ended the Mesozoic era, they survived the extinction and shrank to half the size of their ancestors and their natural predators throughout the Cenozoic were Creodonts (as sub-adults and hatchlings), Entelodonts (as youngsters and hatchlings), bear-dogs (as youngsters and hatchlings), bone-crushing dogs (as younsters and hatchlings), Machairodonts (including the famous Smilodon) (as sub-adults and hatchlings), short-faced bears (as adults and hatchlings), and cougars (as youngsters and hatchlings). They were omnivorous, feeding not only the same food as most ankylosaurids, but in the Eocene, they started to develop stronger teeth to chew and feed on grass, but they also started to eat insects (including their larvae) and carrion of large animals, as an effect of newly evolving large mammal herbivores such as Unitatheriums, which caused the extinction of the last ceratopsians, the Micropachyrhinus and the Triceratus. We don't know what caused the extinction of the Nanotankylosaurus (the last ever ankylosaurids), but it is possible that it was overhunted to extinction by early humans, which were probably also responsible for overkilling most other large species of North America.