Diplodocus

The Diplodocus is a multi-part fossil that can be donated to the museum. In there are five parts in total whereas in, there are six.

In New Leaf
"The diplodocus was a herbivore of the late Jurassic period sporting a tremendously long tail and neck. The neck was so long that, from snout to tail, its length could reach a staggering 175 feet long. Evidence suggests it would use its long, slender tail like a whip to defend itself from attackers."

In New Horizons
"Good old Diplodocus—what would we do without you? This stout fellow embodied all the best in dinosaurs. Those sturdy legs, that magnificent tail, and, above all, that extraordinary neck! Did you know that its center of gravity was such that sitting up on its hind legs was probably easy? What's more, paired with its long neck, this ability greatly increased its reach for eating plants! Best of all, Diplodocus probably grew its entire life, having no 'adult size.' Would that we were all so gifted!"

In Real Life
Diplodocus was a sauropod dinosaur and one of the longest known, with Diplodocus carnegii reaching 24 meters in length. It lived during the Late Jurassic in modern-day North America. The teeth of Diplodocus were of a highly unusual shape for sauropods, likely to give the creature access to different forms of vegetation. This would limit competition, as Diplodocus shared its environment with numerous other sauropod species, all herbivorous. Diplodocus also sports an unusually long tail, with far more vertebrae (80 in fact) than many of its contemporaries and ancestors. Some possible uses for the tail include defense and communication (by using the tail like a whip).