👉 Plagiodontia is a group of extinct mammals that lived in the Late Cretaceous period, around 68-54 million years ago. They were known for their large size and long bones, which allowed them to be able to walk on two legs. Plagiodontians had a wide range of body shapes and sizes, from small herbivores like the Tigrisaurus to larger carnivorous mammals like the Mammutia.