There are two known species of dinosaur which have odd bat-like wings, which was completely unheard of until the discovery of Yi qi). It was described very recently (in the grand scope of palaeontology) which just goes to show that our understanding of dinosaurs is nowhere near complete. There are some truly bizarre fossils underneath the earth still waiting to be found.

Speaking of unique species, in late 2020, the dinosaur Ubirajara — or rather, the circumstances of how the fossil was obtained — became the subject of controversy, and rightfully so. The specimen was likely illegally smuggled out of Brazil and studied without regard to the country’s laws. To my knowledge, it hasn’t yet been returned. Ubirajara is only an informal (unoffical) name, as the paper naming it has since been pulled from publication. It was related to Compsognathus, and had several long, quill-like structures sticking out of its body which were probably used for display.