Apatosaurus

The Apatosaurus is a three-part fossil that can be donated to the museum in all Animal Crossing games to date.

Completing the Apatosaurus in Animal Crossing
"At long last... Apatosaurus is complete! Tremendous! Striking! Massive in every sense of the word! Hoo, I say, hootie hoo! What a truly glorious find! My cup runneth over! Now let me see here... Where shall I begin? Apatosaurus... Hmmm... It lived in the late Jurassic period, and was a member of the diplodocid family of long-necked sauropods. You may be more familiar with the name brontosaurus, though that is a separate species of the same genus. It grew to some 70 feet in length. It had a small head, a long, thick neck, and an amazing whip-like tail, wot! Cra-ack! Whup-pshh! Oh, dear! Awfully sorry! I was envisioning myself with a massive tail! Hoo hoo!"

Completing the Apatosaurus in Wild World
"The apatosaur was once called a brontosaur, I'll have you know. It is well known for having a rather long neck and tail and for being an herbivore. However, it appears that, unlike the giraffe, it could not make its neck vertical! Yes, blood flow, you see. If it straightened more than 90 degrees, it might faint! Ah. Hoo. Terribly sorry. If I kept speaking at that rate, I might have fainted!"