Phylum Chordata

Abstract

The phylum Chordata, which includes the vertebrates, is the largest deuterostome group, and the most recently emerged in terms of geological time. While the invertebrate fossil record extends back over 1,600 million years, fossils of the earliest vertebrates are only 500 million years old. However, in spite of their relatively recent emergence, chordates have established themselves as one of the major animal phyla, with dominance of the water, land, and air. They cannot rival arthropods in terms of numbers of either species or individuals, but outstrip them in terms of total biomass and ecological dominance.