The Dryolestida (formerly known as the Pantotheria or Eupantotheria) are an extinct order of mammals related to the living marsupials and eutherian (placental) mammals. Along with the closely related symmetrodonts, they were the most diverse group of mammals during the Jurassic. They are often found in some of the same quarries that yield the giant sauropod dinosaurs. Most were about the size and shape of a shrew or mouse, with teeth adapted for chopping up a diet of insects, and they apparently were adapted for living in trees like squirrels.