Event 21

95-65 million years ago

Elasmosaurus and Criorhyncus
A herd of herbivorous duck-billed Hadrosaurus dinosaurs from the later Cretaceous, about 70 million years ago. This dinosaur family was the first to be discovered in North America in the 1850’s.
Credit: Illustratrion by John Sibbick, courtesy of John Sibbick Illustration. This illustration is used with permission. All rights reserved.

A golden age of dinosaur evolution occurred during the later Cretaceous Period between approximately 95 and 65 million years ago. The climate was warm then, with higher sea levels and no ice at the poles. This was the time period of many of the famous dinosaurs, including meat-eaters such as Tyrannosaurus and Velociraptor, (both featured in the somewhat misnamed movie “Jurassic Park”), Oviraptor,and plant-eaters such as the three-horned Triceratops, the duck-billed Hadrosaurus, and the armored and spike-tailed Ankylosaurus. All indications were that dinosaurs would continue to be the dominant animal form for millions of years into the future, but, as we will see in the next event, Fate had other ideas…

During the late Cretaceous aquatic reptiles also lived in the seas which teemed with fish, sharks and ammonites (chambered, nautilus-like animals). Placental mammals become more common during this time, although they still tended to be small in size. Flying reptilian pterosaurs were slowly being outcompeted by feathered birds. Flowering plants diversified during this period, and due to plate tectonics the Atlantic Ocean continued to widen between the Americas and Africa/Europe.

Elasmosaurus and Criorhyncus
This Cretaceous marine scene shows the flying pterosaur reptiles, Criorhynchus, the giant plesiosaur Elasmosaurus, and some gull-like birds.
Credit: Illustratrion by John Sibbick, courtesy of John Sibbick Illustration. This illustration is used with permission. All rights reserved.


The fossil record from well-dated deposits in virtually every continent contains dinosaur fossils from this time period. Dinosaurs had become very abundant and also very diverse by this time in their evolution and were living and competing with each other all over the world.


Although dinosaurs were not our ancestors, they were the dominant life form for 150 million years. During this time, our ancestors – the early mammals – were coevolving with the dinosaurs, and, as we shall see, these mammals would eventually come to replace the dinosaurs rise to the top of the food chain. The long reign of the dinosaurs and their fairly sudden end is a reminder to us that the tables can turn in life rather suddenly, and even long-term success in evolution is no guarantee of future success.







This Discovery Channel websites is a really good one about dinosaurs that has a lot of interactive videos and reading materials.

This website has a lot of information about dinosaurs for kids.

This is a comprehensive, but kid-friendly, website about dinosaurs by Enchanted learning.




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