Eriptychius tells us how we got our braincase

[Halichoeres]

Eriptychius is known from the Ordovician of Colorado; it's not super complete, but there is a 3d-preserved cartilaginous braincase that researchers CT scanned for this study. It's way down the gnathostome stem (that is, it's more closely related to jawed vertebrates than to lampreys, but not by much). They find that it grew in the space between the brain and the dermal skeleton (the outer sheets of bone that form the shields of early jawless fish, and our own skull roof and much of our face). This is a lot like us, but dissimilar from living jawless fishes.

A sample of the scans:


Open access in Nature, for which the authors would have paid £8,490: https://www.nature.com/articles/s41586-023-06538-y

[Saarlooswolfhound]

Wow, thank you for sharing!

[Halichoeres]

CNN has some coverage, wasn't expecting that!
https://www.cnn.com/2023/09/21/world/jawless-fish-eriptychius-americanus-3d-fossil-scn/index.html