The phytosaurs were the Triassic
predessesors to the crocodilians. 
And they were huge!  Up to 40ft  long!)
They were an ancient thecodont reptiles
and surprisingly, were not that closely
related to alligators and crocodiles, even though
they looked so very much like them. 
But unlike the crocs, phytosaurs had their nostrils
set way back on their snouts, up close to their eyes. 
And their forward-most teeth were severe shearing blades.  They were specially adapted for catching fish, but they would have been absolutely lethal against even the dinosaurs.  However, they would be extinct by the beginning of the Jurassic period, when real crocodilians would come in to fill their niche.