Valvatida is an order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of sea star

Sea star

Starfish or sea stars are echinoderms belonging to the class Asteroidea. The names "starfish" and "sea star" essentially refer to members of the class Asteroidea...

 in the class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Asteroidea, which contains 695 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in 165 genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 in 14 families. The order encompasses both tiny species, which are only a few milimetres in diameter, like those in the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 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

Tube feet

Tube feet are the many small tubular projections found most famously on the oral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures.Tube feet function in...

. 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.

Families

• Acanthasteridae
• Archasteridae
• Asterinidae
  Asterinidae
  Asterinidae is a large family of sea stars in the order Valvatida. It contains twenty-five genera.-Genera:*Ailsastra O'Loughlin & Rowe, 2005*Allopatiria Verrill, 1913*Anseropoda Nardo, 1834...
  
  
• Asterodiscididae
• Asteropseidae
  Asteropseidae
  Asteropseidae is a family of sea stars. Members of the family have relatively broad discs and five short tapering arms.-Genera:The following genera are listed in the World Register of Marine Species: *Asteropsis Müller & Troschel, 1840...
  
  
• Chaetasteridae
• Ganeriidae
• Goniasteridae
  Goniasteridae
  Goniasteridae are a large family of sea stars. About 260 extant species within 70 genera are currently known. They occur predominantly on deep-water continental shelf habitats in all the world’s oceans, being the most diverse in the Indo-Pacific region...
  
  
• Leilasteridae
• Mithrodiidae
• Odontasteridae
  Odontasteridae
  Odontasteridae is a family of sea stars. Members of the family are known as cushion stars and have relatively broad discs and five short tapering arms.-Genera:The following genera are listed in the World Register of Marine Species:...
  
  
• Ophidiasteridae
  Ophidiasteridae
  Ophidiasteridae is a family of sea stars with about 30 genera. Occurring both in the Indo-Pacific and Atlantic oceans, ophidiasterids are greatest in diversity in the Indo-Pacific...
  
  
• Oreasteridae
  Oreasteridae
  Oreasteridae is a family of sea stars in the class Asteroidea.Selected genera=* Acheronaster H.E.S.Clark, 1982* Anthaster Döderlein, 1915* Anthenea J.E.Gray, 1840* Astrosarkus Mah, 2003* Bothriaster Döderlein, 1916...
  
  
• Podosphaerasteridae
• Poraniidae
• Pseudarchasteridae
• Sphaerasteridae †