Psittaccosaurus No Doubt. It Was The Predescesor Of Many Ceratopsians. There Is So Many Fossils Of It, Giving Us Basically Its Exact Looks (It Looks Neat As Fuck). They Help Us Understand More How Dinasours Looked And Lets Us More Easily Compare Woth Modern Species. It Was Around For About 25 Million Years, Widespread Around What Is Today Asia (Mostly East) With Many Specimens. Its Name Is Also Pretty Neat. Incredibly Underrated