Live Vertebrates

The Vertebrata, or vertebrates, is a very diverse group, ranging from lampreys to Man. It includes all craniates, except hagfishes, and are characterized chiefly by a vertebral column, hence their name.

The majority of the extant vertebrates are the jawed vertebrates, or gnathostomes, but lampreys are jawless vertebrates. However, in Late Silurian or Early Devonian times, about 420 to 400 million years ago, the situation was reverse, and the majority of the vertebrate species were jawless fishes (the “ostracoderms”, presumably more closely related to the gnathostomes than to lampreys). The decline of the jawless vertebrates and the subsequent rise of the gnathostomes took place about 380 million years ago.