Cretaceous

This was the last period of the dinosaurs' rule. Now the transition from the jurassic-cretaceous was a lot slower and less chaotic but it was still enough that the dinosaurs had to evolve. Whereas the apex predator of the Jurassic was Allosaurus, a huge theropod carnivore that would use its sharp teeth and strong skull to slice open its prey. During the transition, allosaurus went extinct. This allowed a new group of carnivores to rise and evolve to become the new apex predators of earth. These were called the carcharodontosaurs. These included dinosaurs such as giganotosaurus, acrocanthosaurus, coelurosaurs, concavenator, etc. For most of the cretaceous period these were the apex predators. There was another group of large carnivores known as the spinosaur family. These dinosaurs were specifically designed to hunt fish. Some had long claws and arms and would use them to grab fish out of rivers or ponds. Others would use their sensitive snout to sense fish movement and then grab them with their crocodilian-like jaws. Some could even swim and would go into the water to find their prey.The transition also did not help the sauropods either, for even though sauropods were very diverse and widespread in the Jurassic, their numbers started to decline after the transition to the cretaceous. This could have been caused by the increase in large carnivores which would have hunted more and more sauropods causing their numbers to decline. This caused the shorter herbivores like the ornithischians, specifically the ankylosaruria family, the ceratopsians and the hadrosauridae family, to rise up and become the new dominant and most widespread herbivorous dinosaurs. But some sauropods survived and these would become the titanosaurs, the largest species of sauropods in history. The titanosaur group included species such as argentinosaurus, patagotitan, dreadnoughtus, etc. though the rule of the carcharodontosaurs lasted for most of the cretaceous, it did not last forever. For there was a new species that would eventually rise up and over through the carcharodontosaurs. These were a group of small, intelligent theropod carnivorous dinosaurs known as the tyrannosaur family.