Tyrannosaurus rex

The Tyrannosaurus Rex is a three-part fossil that can be donated to the museum in all Animal Crossing games to date. It is the highest-scoring fossil (when complete) in terms of HRA points.

Completing the T-Rex in Animal Crossing
"Why, this means... Yes! Tyrannosaurus! It’s complete!!! Oh, such joy! Such unfettered delight! Truly... this is splendid. I am quite beside myself. I’m practically molting with all this excitement! Now then, where to begin? Tyrannosaurus... A magnificent beast... A highly evolved theropod, the ‘tyrant lizard’ was one of the largest carnivores of the late Cretaceous period. It had a large head, a short, muscular neck, a barrel-like body, and powerful hind legs with three-taloned feet. Its skull was enormous, and its vast jaws were filled with dagger-like teeth, the largest of which were 6 inches long! T-rex was 40 feet long from nose to tail. Resistance to its powerful attacks was an exercise in futility! Garrrr! Oh my! Oh, terribly sorry! I beg your pardon, eh wot? I seem to have been overcome by momentary savagery. Hoo!"