Hall of Ancient Life: Paleozoic Era

The Paleozoic Era began with a ‘bang’—the so-called “Cambrian Explosion” – an interval of some 20 million years during which complex, multicellular animals became abundant in the oceans. In Cambrian rocks we find the first fossil remains of many groups of modern marine animals. The limestone that can be seen along I-35 where it cuts through the Arbuckle Mountains was formed in shallow seas that covered Oklahoma in the early part of the Paleozoic.

The Cambrian Period, 514 million years ago.

During the Pennsylvanian Epoch (318 to 299 million years ago), Oklahoma was located on the equator and was covered by vast swamps that became the coal we mine.

In the Permian Period (299 to 251 million years ago), Oklahoma drifted northward and dried out, yielding red sandstones that produced the characteristic red soils extending across much of the western part of the state.

Trilobite

The Paleozoic Era ended with a devastating mass extinction that wiped out 85 to 90 percent of marine animals and 70 percent of life on land, eclipsing the more famous extinction that wiped out the dinosaurs hundreds of millions of years later. Scientists still do not know what caused this extinction. Possible explanations include increased volcanic activity, a large meteorite that hit Australia, changes in climate and changes in oxygen levels in the oceans.

INVERTEBRATES—animals without backbones

During most of the Paleozoic, Oklahoma was covered by a broad, shallow, tropical sea. In that sea lived an abundance of invertebrates including many which are now extinct, such as edrioasteroids, blastoids, and trilobites (like Isotelus shown at right), as well as some which still exist today such as starfish, brachiopods, clams and snails. This exhibit includes dozens of specimens from Oklahoma and around the world.

VERTEBRATES—animals with backbones

Conifer

Edaphosaurus

Living in the same seas as invertebrates were vertebrates such as early fish and sharks. Vertebrates moved out of the water at the end of the Devonian Period, around 360 million years ago, and by the Permian Period, they were well established on land. Permian exhibits feature fossils of Oklahoma’s early amphibians and synapsids – relatives of the first mammals – including the sail-backed plant eater Edaphosaurus and the meat-eating Dimetrodon.

PLANTS

The first plants moved onto dry land during the Ordovician Period, 488 to 444 million years ago. By the UpperCarboniferous Period, much of Oklahoma was covered by vast swamps, home to many ferns and horsetails. During the Permian Period, ginkgos and early conifers had appeared.