What is "hadrosteus"

Hadrosteus rapax ("Rapacious Strong-Bone") is a large arthrodire placoderm from the Late Frasnian Kellwasserkalk facies of Germany. It had large, double-pronged inferognathals, and serrated edges along its mandible, strongly suggesting that it was a fish-eating predator. The head had a triangular snout, and the trunkshield was short, but high, with a median dorsal plate that was broader than wide. The average skull length is about 16 centimeters.