As the Paleozoic era continues, we see the first appearance of  land creatures, such as mites, ammonites, crabs, ground insects, and spiders.

The Devonian is a geologic period of the Paleozoic era. It is named after Devon, England, where rocks from this period were first studied.

During the Devonian Period the first fish evolved legs and started to walk on land as tetrapods, and the first arthropods like insects and spiders also started to colonize terrestrial habitats.

The first seed-bearing plants spread across dry land, forming huge forests. In the oceans, fish diversified into the first sharks, and the first lobe-finned and bony fish. The first ammonite mollusks appeared, and trilobites, the mollusc-like brachiopods, as well as great coral reefs were still common. The Late Devonian extinction severely affected marine life.

The Devonian is usually broken into Early, Middle, and Late subdivisions. The rocks corresponding to these epochs are referred to as belonging to the lower, middle, and upper parts of the Devonian System.

Towards the end of the Devonian period, amphibians began to colonize the land.  The first ferns also grew and true seed plants eventually emerged. The Devonian period also saw many new groups of fish evolve.