Phylum Hemichordata, Urochordata and Cephalochordata
- Illustrated description of these three phyla, and the three classes within Urochordata. Also information on the larval stages, when they form part of the plankton.
- http://www.mba.ac.uk/nmbl/publications/occpub/guide/section17.pdf

Chordata
- Overview of the taxonomy of Phylum Chordata, which includes the well-known vertebrates (fishes, amphibians, reptiles, birds, mammals), hagfishes, tunicates, and lancelets.
- http://tolweb.org/tree?group=Chordata&contgroup=Animals

Vertebrata
- Introduction to the vertebrates and their classification, including the Hyperoartia, or lampreys, and the Gnathostomata, or jawed vertebrates.
- http://tolweb.org/tree?group=Vertebrata&contgroup=Craniata

Subphylum Vertebrata
- What makes a vertebrate a vertebrate? They have more in common than a backbone. Find out more from the Animal Diversity Web.
- http://animaldiversity.ummz.umich.edu/vertebrata.html

Gnathostomata
- Philippe Janvier's article about the jawed vertebrates in the Tree of Life website.
- http://ag.arizona.edu/ENTO/tree/eukaryotes/animals/chordata/gnathostomata.html

Phylum Chordata
- Brief introduction to the chordates, defined as organisms that possess a structure called a notochord, at least during some part of their development. Includes links to information about subgroups and representative animals.
- http://animaldiversity.ummz.umich.edu/chordata.html