The Devonian is a geological period that lasted from about 419 to 359 million years ago. It is often referred to as the "Age of Fishes" because of the significant diversification and dominance of fish during this time. The period is characterized by the appearance of early tetrapods, which are the ancestors of all land vertebrates. During the Devonian, the Earth's climate was generally warm, and large shallow seas covered much of the land. This period saw the development of the first forests, with plants like lycophytes and ferns becoming more widespread. The Devonian ended with a major extinction event that affected marine life and paved the way for new species in subsequent periods.