Tarasiiformes is an extinct order of prehistoric ray-finned fish.

[1] Tarrasius is an extinct genus of Tarasiiformes.

Tarrasius problematicus (of Mississippian origin, ~ 350 Ma) featured a fully regionalized tetrapod-like spine divided into 5 distinct segments.

[5][6] It is not considered a transitional fossil though, but an extreme example of convergent evolution.