Hall of Ancient Life: Mesozoic Era

TRIASSIC PERIOD 200 to 251 million years ago

During the Triassic Period, the continents were united in one huge landmass called Pangaea. Oklahoma was, at that time, located near the equator, but far from the ocean. Not much is known about the climate during this period, but it was likely warmer and increasingly dry. Two important groups of vertebrates-dinosaurs and mammals-appear for the first time during the Triassic Period.

Dinosaurs evolved from a line of vertebrates, known as archosaurs, that had many adaptations for running, including changes to their hips and ankles.

Eoraptor

Instead of the sprawling, legs-out-to-the-side posture of lizards and alligators, the first dinosaurs walked on two legs with their legs directly beneath their body. This made them much more efficient runners. Early dinosaurs, including Eoraptor shown here, were small animals, only about 2 feet tall.

Mammals evolved from a line of vertebrates called therapsids that had special adaptations for chewing food. Early mammals were very small and active. The amount of time an animal can be active depends on how fast it can change food into energy. With new muscles and more complex teeth, mammals could change food into energy quickly. By examining tiny fossil jaws and teeth, paleontologists can trace the history of mammals. This exhibit allows visitors to look through a magnifying glass to examine and compare the jaws and teeth of some of the earliest mammals.

Similar features in unrelated species

Convergent Evolution
Even though dinosaurs and mammals are not closely related to each other,
we see similar changes to their hips during this period so that their legs can be held beneath the body, rather than out to the side. When two unrelated groups of animals or plants evolve features that are very similar, biologists call this process "convergent evolution." This exhibit illustrates the idea of convergent evolution with
examples of the skulls of a prehistoric phytosaur and three very different modern animals: the gar (fish), the gavial (a crocodile relative), and the dolphin
(a mammal). Though unrelated, all these animals are water dwellers who
feed on fish. Over time, each separately evolved a similar long snout with sharp pointed teeth - an effective tool for slicing through water to catch fish.

JURASSIC PERIOD 200 to 145 million years ago

During the Jurassic Period, North America was moving slowly northwest and began to split away from the continents of South America and Africa, forming an inland sea. By the late Jurassic, this sea had widened and formed the Gulf of Mexico, as well. Oklahoma was still much nearer the equator than it is today, and drier than it was during the Triassic, with desert-like areas. Life on land was dominated by the dinosaurs.

Saurophaganax Maximus

The centerpiece exhibit in the Hall of Ancient Life, the Jones Family "Clash of the Titans," shows an encounter between Oklahoma's largest Jurassic animals - the plant-eating sauropod Apatosaurus, which, at more than 93 feet long, is the largest of its kind in the world, and the carnivorous theropod Saurophaganax maximus, the largest of the Jurassic predators. Saurophaganax was named Oklahoma's official State Fossil in 2000, and has so far been found only in Oklahoma. Recent finds in New Mexico may be Saurophaganax, but are not confirmed. Because of the enormous weight of some of these fossils (up to 600 pounds for a single bone in some cases), the museum chose to mount casts instead of the actual fossils, but you can see and touch a real Apatosaurus leg bone and view a real Saurophaganax foot in nearby displays.

The bones of these huge animals were found in Oklahoma's panhandle, the only part of Oklahoma with rocks of Jurassic age. These rocks are part of the Morrison Formation, a formation famous for its dinosaur fossils. Only the southeastern edge of the Morrison Formation dips into Oklahoma - just catching the western tip of the Panhandle. The rest of it stretches across Colorado, Wyoming and Montana, and extends into Utah, New Mexico, and the Dakotas.

Beneath these Oklahoma giants, Archaeopteryx, the first known bird, is hunting down a small mammal. The oldest fossil birds were found along with dinosaurs in the now-famous Solnhofen Quarry in Germany. Solnhofen mud limestone is so fine that it preserved impressions of the Archaeopteryx's delicate feathers. A replica of the original Archaeopteryx specimen is on display in the Jurassic area, along with a comparison of the key characteristics that link certain Jurassic dinosaurs to modern birds.

Although no Jurassic birds have been found in Oklahoma, the Panhandle has yielded fossils from hundreds of Jurassic sauropod and theropod dinosaurs. These sites have also yielded fossils of apatosaurs ranging in age from baby to adult. Our museum has one of the best collections of juvenile sauropod bones in the nation. You can see some of the baby Apatosaurus bones on display near the world's largest adult Apatosaurus. Studying the fossil skeletons of dinosaurs of different ages can provide clues as to how they lived and how fast they grew.

CRETACEOUS PERIOD 145 to 65 million years ago

Pteranodon

During the Cretaceous Period, the continents began to break apart and separate much more dramatically than before. North America drifted far north of where it had once sat on the equator during the Permian Period. The climate was unusually warm, perhaps because of increased volcanic activity associated with the movement of the continents. Sea levels rose and a great shallow sea extended from the Gulf of Mexico to Alaska, splitting North America into two separate landmasses and covering much of Oklahoma.

In rock formed at the bottom of this sea, paleontologists have discovered fossils of animals that lived in or flew over this marine environment. Platecarpus (a mosasaur, or giant marine lizard, related to the Komodo Dragon), Xiphactinus (a large carnivorous fish) and Pteranodon (a pterosaur) can be seen in the museum's marine Cretaceous diorama.

Deinonychus

During this time, parts of southeastern Oklahoma were on the coast of this great shallow sea. On land, herds of tenontosaurs - large duck-bill-like plant eaters - were prey to the small but efficient predator Deinonychus. Deinonychus is the dinosaur after which Steven Spielberg modeled the terrifying "Velociraptors" depicted in "Jurassic Park." Though Deinonychus is not nearly as large as the movie dinosaurs were, actual Velociraptors were smaller still, with a narrower skull. Spielberg liked the look of Deinonychus and the name Velociraptor so he married the two for the movie. He then made it nearly twice the size of Deinonychus to increase its fear factor. Strangely enough, the year the movie was released, paleontologists unearthed Utahraptor - a six-foot-tall dinosaur that looks much like Spielberg's made-up Velociraptor.

The museum's coastal Cretaceous exhibit features a Tenontosaurus mother and her offspring under attack by a pack of Deinonychus. You can learn how museum paleontologists studied how bones and teeth of both animals were arrayed at a site in Atoka County to discover clues to what may have happened there.

Examine our Pentaceratops skeleton and imagine yourself standing toe-to-toe with this imposing plant eater. Its skull - at ten-and-a-half feet tall - is the largest of any land animal ever found, and is recognized by the Guinness Book of World Records as the world's largest dinosaur skull. Like most of its relatives, Pentaceratops possessed a bony frill that not only protected its neck, but may have served to display its strength and health to others of its kind when seeking a mate. This specimen is about 70% complete and is the only fully-mounted Pentaceratops in any museum.

Pentaceratops

Flowering plants, or angiosperms, appeared for the first time during the Cretaceous period, about 135 million years ago. They diversified and thrived - and over the next 75 million years, they came to be the dominant plant form on the Earth, spreading quickly and adapting to many different environments. Today angiosperms make up most of the species we see around us every day such as weed and garden plants. An exhibit in the Cretaceous area allows visitors to look through a magnifying lens to view tiny fossilized flowers that are 85 million years old.

At the end of the Cretaceous period, 65 million years ago, a mass extinction occurred that wiped out all of the dinosaurs except birds, along with about 85% of all other animals on the Earth. Learn about the giant meteor that may have struck the Earth at this time, and the subsequent climatic changes that may have caused this extinction. This exhibit includes the Keyes meteorite: a chunk of stony space debris weighing more than 300 pounds that was found in Keyes, Oklahoma, in 1939.