Pelycosaurs were the largest land animals before the dinosaurs. Permian period.
Courtesy of the Field Museum, Chicago.
The geological era that began about 570 million years ago and ended 240-250 million years ago is called the Paleozoic--"Ancient life."
FOSSILS
Before the Paleozoic there are few fossils. In the early Palezoic so many "new" forms of life appear that paleontologists refer to the "Cambrian explosion." In early Paleozoic rock there are abundant invertebrates. The first fossils of fish and of invertebrate land animals appear in Silurian rock about 440 million years old. Land animals with backbones--amphibians--first appear in Devonian rocks in the mid-Paleozoic, about 410 million years old. The first fossils of reptiles appear in the "Pennsylvanian" age late in the Paleozoic. Trilobites of many kinds swam in the Paleozoic seas, but many of the sea animals were immobile. The latest appearance of trilobites and of seed ferns is in the latest Paleozoic (Permian period) rock.
Pelycosaurs were the largest land animals before the dinosaurs. Permian period.
Courtesy of the Field Museum, Chicago.
GEODYNAMICS
At the beginning of the Cambrian shallow seas were extensive. Thick layers of sediment were deposited. The Appalachian mountains began to be built. In the Mississipian, the seas extended over much of the continents. At the end of the Paleozoic there was extensive uplift of mountains. Basalt-flood volcanism took place at the end of the era.
CLIMATE
In Silurian times, eastern North America was desert. Later, in the Pennsylvanian, great coal swamps formed in Europe and North America.