Onchopristis

Name Meaning:  Barb Saw

Geologic Era:  Cretaceous

Estimated Range:  Modern North Africa

Location Found:  Morocco

Estimated Size:Up to 8 meters long

Extinction Date:  Late Cretaceous

This is a rostal (nose) barb from a giant sawfish-like animal. Recently, Onchopristis has been reclassified as a very derived skate, similar to rays.  The most unique feature of this tooth is the barb toward the distal end, which would have functioned in the capture and holding of prey items.  There would have been several dozen of these tooth barbs per skate rostrum.  This setup is similar to that seen in modern sawfish.  Onchopristis would have shared its environment with sharks, elasmosaurs, and several mosasaur species.  If it happened to venture into rivers from the sea, it could also have come into contact with suspected piscivores like Spinosaurus.  

Contrary to appearances, Onchopristis was more closely related to sharks and rays than to bony fish.  This means that much of its skeleton was cartilage, which tends not to fossilize well.  What few remains of Onchopristis that have been recovered tend to be the barbs and parts of the rostrum.  These pieces alone are enough to suggest the large size of this fish.  Sawfish hunt by sweeping the bottom of the seafloor with their rostrum, or just waiting for a desirable prey item to pass.  When this happens, the sawfish quickly swings its rostrum at the prey, stunning or possibly killing it with its barbs. 

The rostrum is the main sense organ of sawfish, so it can be assumed that Onchopristis, like its modern relatives, had rather poor eyesight.  Most of the remains of Onchopristis have been found in Morocco, but it probably had a worldwide distribution.  Modern sawfish species are considered to be endangered due to habitat loss and overfishing, though many species of rays are thriving.. 

Image Credits:
Life Reconstruction:   http://spinops.blogspot.com/2014/03/onchopristis-numidus.html