Protopsephurus liui (skull)

This is a closeup of the skull of this Protopsephurus liui. You can easily see here the namesake of the paddlefish: the long paddle-shaped rostrum. Scientists first thought the fish would use the paddle to sift through stones searching for food. This is why the name Protopsephurus was used because it translates to "first pebble bearer" (can also be considered as "first pebble holder"). Nowadays we know this is not how the rostrum was used. Tiny hair sensors line the rostrum, and these sensors act as a hyper sensitive radar. The eyesight of paddlefish is considered relatively poor so the animal would need these sensors to hunt successfully. 

Other notable features here are the wide fenestrae and the gapping jaw. The fenestrae were likely designed to be wide so the skull would be lighter, the reduced weight would help the fish with making quick movements. The wide jaw is clearly here in this specimen (the curve shaped bone towards the bottom of the skull). The fish would open its gaping maw and suck down any food it could fit in its mouth. Prey items would have been small invertebrates and small fish.