Eusthenopteron

The eusthenopteron is a stand-alone fossil in.

Triva

 * Blathers's description of the eusthenopteron references the Splatoon series: "Imagine if we'd not left the oceans... How might fashion and music be different in an aquatic world? How would we resolve differences? Perhaps some sort of ink-squirting contest of champions?"

Real-world information
Eusthenopteron was a sarcopterygian (lobe-finned fish) from the Late Devonian. It is a tetrapodomorph, making it more closely related to modern tetrapods (land vertebrates) than to modern lobe-finned fishes like lungfishes and coelacanths. While very much aquatic (unlike later tetrapodomorphs like Acanthostega), it nevertheless exhibits anatomical features exclusive to tetrapodomorphs (including tetrapods), including choana, or internal nostrils, and possibly bone marrow.