What are starfish? Taxonomy.
Kingdom: Animalia
Starfish are animals. And yes, they actually do move, just slowly.
Phylum: Echinodermata
Echinodermata means "spiny skin," and one of the
characteristics of echinoderms is the presence of calcareous ossicles
(essentially tiny bones) in their skin. In some groups, like the
echinoids (sea urchins), these are exaggerated to the point of forming
a shell-like structure, while in the holothuroids (sea cucumbers) they
are reduced or sometimes absent. Echinoderms are also characterized by
a water vascular system. All echinoderms are marine, living in the
ocean.
Aside from the starfish, the other echinoderm groups are the echinoids (sea urchins and sand
dollars), ophiuroids
(brittle stars), holothuroids
(sea cucumbers), crinoids
(sea lilies and feather stars), and the concentricycloidea
(sea daisies; known only from preserved deep water specimens).
There are approximately 7000 living species of echinoderms.
Class: Asteroidea
Asteroids are the starfish. There are approximately 1500
living species of asteroids.
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Order:
There are seven Orders of starfish, the Paxillosida,
Valvatida, Spinulosida, Notomyotida, Velatida, Brisingida and
Forcipulatida. Of these, most intertidal species (and thus the species
you are most likely to have seen) are in the Forcipulata. Many of the
best known species, such as Pisaster ochraceous
(and P. giganteus, P. brevispinus)
and Asterias vulgaris (and A. forbesi,
and so forth) are in the Asteriid family of the Forcipulate order.
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Asterias forbesi. This
species and a similar species, Asterias
vulgarius, are common on the New England coast.
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If you're interested in the details of echinoderm
classification, follow
this link.
Last
updated January 26, 2000.
