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Kingdom: Animalia
Sub Kingdom: Eumetazoa
Super Phylum: Bilateria:Deuterostomia
Phylum: Echinodermata
Sub Phylum: Asterozoa
Class: Asteroidea
Order: Brisingida - Forcipulatida - Notomyotida - Paxillosida - Spinulosida - Valvatida - Velatida


Typically referred to as starfish or sea stars.

Sea stars generally have five arms as a continum from the central disc and the length can vary greatly relative to the oral disc. Under the arms are distinctive ambulacral grooves containing the tube feet which converge at the centre of the oral disc at the mouth. The upper surface of the oral disc has the anus and one or more madreporites in the centre. They are detritus feeders, omnivores or predators. There has been numerous examples of sea stars breeding in captivity (see Starfish Spawning).


The class Asteroidea is divided into 7 orders[1]:

  • Brisingida - deep-sea dwelling, many (6-16) long, attenuated arms used in suspension feeding
  • Forcipulatida - have forcipulate pedicellariae, which are conspicuous on the body surface
  • Notomyotida - deep-sea dwelling, flexible arms with characteristic longitudinal muscle bands along the inner dorsolateral surface
  • Paxillosida - can bury themselves partially under sandy sediments, characterised by pointed, unsuckered tubefeet
  • Spinulosida - relatively delicate skeletal arrangement and completely lack pedicellariae
  • Valvatida - quite diverse, characterized by their conspicuous marginal ossicles
  • Velatida - typically thick body with large discs and interradial depressions




  1. Asteroidae - Tree of Life