Dunkleosteus Share definition Flag A prehistoric fish. Existed during the Late Devonian period. About 358–382 million years ago. Person: Hey dude! Heard of a dunkleosteus? Person 2: Yep. Dunkleosteus by BruoGD June 29, 2017 0 0 Get merch Get the Dunkleosteus mug. Buy Now — $32.95 See more merch