The Mesozoic, also known as the “Age of Dinosaurs,” is the time period from 251 million years ago until 65 million years ago. According to the display at the Raymond M. Alf Museum of Paleontology:
“The first birds, mammal, and turtles all evolved at this time. The earth’s surface transformed from a single giant continent to the general configuration that we see today. But, perhaps most famous are the dinosaurs—which originated around 230 million years ago and disappeared without a trace (except for birds) 65 million years ago. Only the rock record, with its fossils, provides evidence of this life of the past.”
The illustration by John Sibbick shows some of the dinosaurs which once roamed southern Utah.
Richard Dawkins, the Charles Simonyi Professor of the Public Understanding of Science at Oxford University, in his collection of essays entitled A Devil’s Chaplain, writes:
“Modern birds are descended from dinosaurs (or at least from ancestors we would now happily call dinosaurs if only they had gone extinct as decent dinosaurs should).”
Shown below are the Mesozoic displays in the Raymond M. Alf Museum of Paleontology on the campus of the The Webb Schools, a private residential high school, in Claremont, California.
Shown above is a model of the Velociraptor from 75 million years ago.
Shown above is Pachycephalosaurus from 68 million years ago.
The illustration by John Sibbick shows Stegorsaurus.
Shown above is Diabloceratops from 78 million years ago. This is a cast from a find in southern Utah.
Shown above is a cast of Gryposaurus monumentensis, also known as hadrasaur or duck-billed dinosaur. This dinosaur was 35 feet long and weighed up to 3 tons.
According to the Museum display:
“The museum’s important finds in the Kaiparowits Formation in southern Utah, such as this duck-billed dinosaur, have all been discovered by students, staff, and volunteers associated with The Webb Schools.”
Shown above are a turtle shell (bottom), a Hadrosaur skin impression, and a leaf impression.
Shown above is a cast of Centrosaurus, a plant eater from 75 million years ago. Centrosaurus was about 20 feet in length and weighed 2 tons. This one was found in Alberta (Canada).
The Centrosaurus skull.
According to the Museum display:
“Centrosaurus was a close cousin of Triceratops, distinguished mainly by the shape of the facial horns and boney neck frill. Scientists are still debating the purpose of the odd skulls—were the horns and frills for showing off, fighting with another Centrosaurus, defense from predators, or a combination of all these?”
Shown above is the leg bone cast from Camarasaurus, a long-necked, herbivorous sauropod dinosaur.
Shown above is Allosaurus, one of the largest predators of the Late Jurassic period (155 million years ago) in North America. This animal was 36 feet in length and weighed 1.5 to 2 tons.
Another view of Allosaurus with museum visitors providing a sense of scale.
The Allosaurus skull.
Dinosaurs fall into two groups, based on their hip structure: bird-hipped and lizard-hipped.
Shown above is a Hadrosaur specimen.
Shown above is a T. rex skull.
Shown above is a turtle.
Shown above is a turtle shell from 66 million years ago.
Shown above is an ichthyosaur.
According to the Museum display:
“Although dinosaurs ruled the land during the Mesozoic, the oceans were also teeming with life. After evolving on land, many reptiles returned to the water and became quite successful there.”
Shown above is an ichthyosaur.
Shown above is the articulated skeleton of Rhamphorhynchus from 155 million years ago.
Shown above is the disarticulated skeleton of Rhamphorhynchus from 155 million years ago.
Shown above is the cast of a Pterodactylus skeleton.
According to the Museum display:
“During the Mesozoic, a number of flying reptiles shared the world with dinosaurs. These animals, called pterosaurs, are cousins of dinosaurs but are not actually dinosaurs themselves. Pterosaurs came in a variety of sizes, from sparrow-sized to the size of a small airplane. Instead of feathers, pterosaurs had a leathery membrane that formed the body of the wing, similar to bats.”
Shown above is a modern bat wing.
Shown above is an Oviraptor egg from 75 million years ago compared with a recent chicken egg.
Shown above are Sauropod eggs from 80-70 million years ago.
According to the Museum display:
“Like birds, crocodiles, turtles, and many lizards and snakes, dinosaurs reproduced by laying eggs. Discovery of eggs in nests along with the parent dinosaur’s skeleton indicates that some dinosaurs may have cared for their eggs until they hatched (by incubating the eggs and guarding the nest.)”