| Valvatida | |
|---|---|
| Mediaster aequalis | |
| Scientific classification | |
| Kingdom: | Animalia |
| Subkingdom: | Eumetazoa |
| Phylum: | Echinodermata |
| Class: | Asteroidea |
| Order: | Valvatida Perrier, 1884 |
| Families | |
|
14, see text. |
|
Valvatida is an order of sea star in the class Asteroidea, which contains 695 species in 165 genera in 14 families. The order encompasses both tiny species, which are only a few milimetres in diameter, like those in the genus Asterina, and species which can reach up to 75 cm like species in the genus Thromidia. Almost all species in this order have five arms with tube feet. This order is primarily identified by the presence of conspicuous marginal ossicles, which characterizes most of the species. Clamp-type pedicellariae are the main type of pedicellaria in this group.