Arthrodire
A common misconception is the arthrodires were sluggish bottom-dwellers that were outcompeted by more advanced fish. But during their reign, the arthrodires were one of the most diverse and numerically successful vertebrate orders of the Devonian. They occupied a vast spectrum of roles from apex predator to detritus-nibbling bottom dweller. The arthrodires were one of many groups eliminated by the mass extinctions of the late Devonian. This let other fish such as sharks diversify into the vacant ecological niches during the Carboniferous period.