Sand dollars are in the Echinoid (Echinoderms) class of marine animals. When they are living, they are covered with a suit of moveable spines that encompass the entire shell. Like its close relative the sea urchin, the sand dollar has five sets of pores arranged in a petal pattern. The pores are used to move sea water into its internal water-vascular system, which allows the creature to move. Subphyla & Classes Homalozoa Gill & Caster, 1960 Homostelea Homoiostelea Stylophora Ctenocystoidea Robison & Sprinkle, 1969 Crinozoa Crinoidea Eocrinoidea Jaekel, 1899 Paracrinoidea Regnéll, 1945 Cystoidea von Buch, 1846 Asterozoa Ophiuroidea Asteroidea Echinozoa Echinoidea Holothuroidea Ophiocistioidea Helicoplacoidea † Arkarua † Homalozoa † Pelmatozoa Edrioasteroidea† Cystoidea † Eocrinoidea † Edriaosteroidea † Blastozoa † † = extinct Echinoderms (Phylum Echinodermata, from the Greek for... Subclasses Subclass Perischoechinoidea Order Cidaroida (pencil urchins) Subclass Euechinoidea Superorder Atelostomata Order Cassiduloida Order Spatangoida (heart urchins) Superorder Diadematacea Order Diadematoida Order Echinothurioida Order Pedinoida Superorder Echinacea Order Arbacioida Order Echinoida Order Phymosomatoida Order Salenioida Order Temnopleuroida Superorder Gnathostomata Order Clypeasteroida (sand dollars) Order Holectypoida Wikispecies has information related to... A pore, in general, is some form of opening, usually very small. ...

Sand dollars live beyond mean low water on top of or just beneath the surface of sandy or muddy areas. The spines on the somewhat flattened underside of the animal allow it to burrow or to slowly creep through the sand. Fine, hair-like cilia cover the tiny spines. Tubefeet or podia that line the food grooves, move food to the mouth opening which is in the center of the star shaped grooves on the underside of the animal called the oral surface. Its food consists of plankton and organic particles that end up in the sandy bottom. cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ... For the SpongeBob SquarePants character, see Plankton (SpongeBob SquarePants). ...

On the ocean bottom, sand dollars are frequently found together. This is due in part to their preference of soft bottom areas, which are convenient for their reproduction. The sexes are separate and, as with most echinoids, gametes are released into the water column. The free-swimming larvae metamorphose through several stages before the skeleton or test begins to form, and they become bottom dwellers. Animated map exhibiting the worlds oceanic waters. ... For other uses, see Reproduction (disambiguation) Reproduction is the biological process by which new individual organisms are produced. ... A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ... A larval insect A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ... For other uses, see Skeleton (disambiguation). ...

The name "sand dollar" is a reference to their round flat shape, which is similar to a large coin.

The term "sand dollar" can also refer to the test left when a sand dollar dies. By the time the test washes up on the beach, it is usually missing its velvety covering of minute spines and has a somewhat bleached appearance due to its exposure to the sun. Sol redirects here. ...

Suborders and families

• Clypeasterina
  • Arachnoididae
  • Clypeasteridae L. Agassiz, 1835
• Laganina
  • Fibulariidae Gray, 1855
  • Laganidae
• Rotulina
  • Rotulidae
• Scutellina
  • Astriclypeidae
  • Dendrasteridae Lambert, 1889
  • Echinarachniidae Lambert, 1914
  • Mellitidae Stefanini, 1911

Underside of same live sand dollar Genera See text. ... Image File history File linksMetadata Download high resolution version (1177x1047, 276 KB) Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ...

A number of sand dollars on a seabed Sand dollars Caption: 137. ...

Keyhole sand dollar, Mellita quinquiesperforata Image File history File links Download high-resolution version (2040x1752, 143 KB) Keyhole Sand Dollar, Mellita quinquiesperforata, by Sharon Mooney, Sand Dollar File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... It has been suggested that this article or section be merged into Sand_dollar. ...

External links

• Clypeasteroida (TSN 157984). Integrated Taxonomic Information System.
• Ask a Scientist
• The Common Sand Dollar by Cheryl Page