Iguanodon

The Iguanodon  is a three-part fossil in the introduced in  that appears in all subsequent games.

In
After donating the final part of the fossil in, its plaque in the museum will read:

"The iguanodon is so named because it was mistakenly believed to be a large iguana. An herbivore, it is famous for its spikelike thumb claws, which seem somewhat odd on a nonpredator. Supposedly it would run on two legs but would use all four when it was just walking at its leisure."

Real-world information
Iguanodon was an herbivorous ornithopod dinosaur which lived in Europe. It is one of the first named genera of dinosaur, described by Gideon Mantell in 1824 and named by Friedrich Holl in 1829. While multiple species ranging from the Late Jurassic to Early Cretaceous have historically been classified as Iguanodon, reclassification efforts during the 21st century limited the genus to only two species living 126-122 million years ago in the Early Cretaceous. It was up to 10 meters long, weighed 3 tons, and sported a beak with iguana-like teeth (hence the name). Its most notable anatomical feature was a thumb spike, which Mantell originally misinterpreted as a horn on the nose.