The short-necked plesiosaur likely had few enemies, but those that attacked were some of the fiercest monsters of the seas, including sharks with razor-sharp teeth and the giant mosasaur Tylosaurus. One famous Tylosaurus fossil contains the remains of a juvenile Dolichorhynchops inside. And Dolichorhynchops fossils have been found with unborn babies inside, strong evidence they gave birth to live young.