It's less than 2cm long, but this 400 million year old fossil fish changes our view of vertebrate evolution
https://phys.org/news/2018-05-2cm-million-year-fossil-fish.html
Why are we so excited about discovering the structure of an ancient fish skull? Because Ligulalepis sits in a very important position in the vertebrate evolutionary tree.
Fishes are the most diverse group of backboned animals (vertebrates) on the planet, with roughly 30,000 known species.