Build Em Ups DinosaursDid you know. Dinosaurs (almost certainly) evolved into birds! Dinosaurs lived among early mammals (usually high up in trees, out of harm'way) for a large part of the Mesozoic Era. Most of these early furballs were about the size of mice, but a few (like the dinosaur eating Repenomamus) grew to respectable sizes of 50 pounds or so, tiny by T. Rex standards but huge for an ancient mammal. With this set you learn all about dinosaurs with great facts and