The Mesozoic oceans were ruled by giant marine reptiles such as ichthyosaurs, mosasaurs, plesiosaurs, and pliosaurs among others. Since the experiment in my dinosaur book involves recreating a prehistoric ecosystem, I am thinking of introducing my own unique marine reptiles. Just as there will be an apex predator on land, there will be an equally frightening apex predator in the surrounding sea. I have been drawing inspiration from some of the real life monsters of the deep such as Tylosaurus and Liopleurodon. Imagine a marine reptile that is scarier than any killer shark. This leviathan will be one of the final challenges the characters will face as they try to escape a primeval world.