Pteranodon

The Pteranodon is a fossil that can be donated to the museum in all games to date. It is a three or four-part fossil, depending on the game - introduced a fourth part, the body, which was removed in  but re-introduced in.

In Animal Crossing
"First things first, this winged creature is not actually a dinosaur, but rather a flying reptile. It did, however, live among many dinosaurs during the late Cretaceous period. Fascinating, eh wot? The structure of its immense wings suggests that is stayed aloft by gliding rather than flapping, you see? Imagine pteranodons with wingspans of over 23 feet swooping down to catch fish in their pelican-like beaks...Screee...SCHWAAAH!!! Oh, I do beg your pardon. Beaks, wings, flying...It's so very close to home!"

In Wild World
"The pteranodon was simply a wonderful creature. It emerged in the later age of dinosaurs, winging through the ancient skies. Though it could fly, it was most certainly not a bird! No, it was a reptile, wot! When it spread its wings, it was as big as a small airplane. Simply gargantuan! The very thought boggles my brain, to be honest. Ah. Hoo. Yes, so sorry. I'm actually rather glad the brute no longer exists."

In New Leaf
"Pteranodons were a type of winged reptile, perhaps the ancestors of common birds. With their wings spread, they were about the size of a small airplane, but their bodies were very light. Strangely, they weighed less than 50 pounds, with wings made from skin, allowing for ease of flight."

In New Horizons
"The mighty Pteranodon! Among the very largest animals ever to fly, they were role models to us all. With a wingspan of over 23 feet in some cases, I find it simply stunning that they ever did more than glide! But fly they did, soaring dynamically and dramatically over land and sea! I wish I could have seen it... "

In Real Life
The Pteranodon was a pterosaur or flying reptile that had two main species with an average wingspan of 4.2 metres.