Domain Eukarya
Kingdom Animalia
Phylum Echinodermata
Phylum Echinodermata is the phylum most closely related to phylum Chordata, our own phylum. The 6,000 species that make up this phylum do not show body segmentation, and are radially symmetrical when fully grown for the most part. Almost all of the species are marine, although a few can live in brackish water. However, echinoderms are bilaterally symmetrical in the larvae stage, meaning that they are not closely related to animals of phylum Cnidaria, which never show bilateral symmetry.
This phylum is closely related to the chordates because the coelom of the animal is made from the digestive tube, not from cell masses like the phyla Mollusca, Annelida, and Arthropoda. Therefore, echinoderms are deuterosomes. Another relation to our phylum is an endoskeleton, made of 95% calcium carbonate. There are projecting spikes out of the endoskeleton, which is held together by skin tissue. Another hallmark of the echinoderms are hard, spiny skin. This is a common feature, but not always apparent in echinoderms. In fact, the word Echinodermata means "like a sea urchin's skin" in Greek. The uniting feature of echinoderms is a water-vascular system. This is a system of canals branching throughout the body that branch into many sections called tube feet. There are at least 2,000 tube feet, which can penetrate the body wall and skeleton in places called ambulacral grooves, in most echinoderms. These tube feet, and in many echinoderms arms and even organs, can be regenerated. There are five major classes in the phylum Echinodermata.
Here is a list of the classes in the phylum Echinodermata. Click below to see the distinguishing characteristics of these classes.
Phylum Echinodermata