Sand Dollar | Echinoderm - Encyclopedia Britannica

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External Websites

• National Center for Biotechnology Information - PubMed Central - The first complete mitochondrial genome of the sand dollar Sinaechinocyamus mai (Echinoidea: Clypeasteroida)
• The Embryo Project Encyclopedia - Inducing Fertilization and Development in Sand Dollars
• Smithsonian Library and Archives - DSpace Repository - Phylogeography of the sand dollar genus Mellita: Cryptic speciation along the coasts of the Americas (PDF)
• Middlebury - Lapis Sand Dollars
• Nature - Scientific Reports - Phylogeny, ancestral ranges and reclassification of sand dollars
• CiteSeerX - Extinct and extant sand dollars (Clypeasteroida: Echinoidea) from Uruguay (PDF)
• AZ Animals - Sand Dollar

Britannica Websites Articles from Britannica Encyclopedias for elementary and high school students.

• sand dollar - Student Encyclopedia (Ages 11 and up)

sand dollar echinoderm Ask Anything Homework Help Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors History Britannica AI Ask Anything Homework Help Table of Contents Table of Contents Ask Anything

sand dollar, any of the invertebrate marine animals of the order Clypeastroida (class Echinoidea, phylum Echinodermata) that has a flat, disk-shaped body. They are close relatives of sea urchins and heart urchins. The sand dollar is particularly well adapted for burrowing in sandy substrates. Very small spines used for digging and crawling cover the entire surface of its body and are appressed backwards toward the posterior anus. The mouth is located in the centre of the body’s underside. The upper surface exhibits pentaradiate symmetry, with a pattern of five “petals” spreading out from the centre. Some species found stranded on the shores of North America have five or six slots, or lunules, through the test (external skeleton). Most sand dollars measure from 5 to 10 cm (2 to 4 inches) in diameter. Species of comparable size occur in shallow coastal waters throughout the rest of the world, except in Europe and Antarctica.

This article was most recently revised and updated by John P. Rafferty.