Wildlife
Chordates include all the vertebrates and some invertebrate allies that possess, for part or all of their lives, a structure called a notochord. The notochord is a stiff rod that helps support the body and runs parallel to the main nerve cord. In the vertebrates, these have evolved into the spinal column, which is reinforced and protected by cartilage or bone. The allied invertebrates in the chordates phylum include members that only have the notochord for part of their life: the sea squirts, lancelets and hagfish.
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Devonian fishing
Fossil fish in Scotland's quarries tell the story of our backboned ancestors.
Beautiful fossil fish can be found in the quarries of Orkney and Caithness. This programme was first shown in 1997.
Unsophisticated relatives
All backboned animals, even humans, are descended from sea squirts and slimy hagfish.
All backboned animals, even humans, are descended from sea squirts and slimy hagfish.
The shading illustrates the diversity of this group - the darker the colour the greater the number of species. Data provided by WWF's Wildfinder.
Chordates, members of the phylum Chordata, are deuterostome animals possessing a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail for at least some period of their life cycles. Taxonomically, the phylum includes the subphyla Vertebrata, including mammals, fish, amphibians, reptiles, birds; Tunicata, including salps and sea squirts; and Cephalochordata, comprising the lancelets.
The phylum Hemichordata including the acorn worms has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. It, along with the echinoderm phylum, including starfish, sea urchins, and sea cucumbers and their kin, are the chordates' closest relatives. Primitive chordates are known from at least as early as the Cambrian explosion.
There are more than 75,000 living species of chordates, about half of which are bony fish of the class osteichthyes. The world's largest animal, the blue whale, and fastest animal, the peregrine falcon, are chordates.
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Amphibians
Birds
Mammals
Reptiles
Cartilaginous fish
Lampreys
Bony fish
Synapsids