''Echinarachnius parma'', the common sand dollar, is a species of
sand dollar
Sand dollars (also known as a sea cookie or snapper biscuit in New Zealand, or pansy shell in South Africa) are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are k ...
native to the Northern Hemisphere. Kroh, A.; Mooi, R. (2020). World Echinoidea Database. Echinarachnius parma (Lamarck, 1816). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=158062 on 2020-12-31
;Subspecies:
* ''Echinarachnius parma obesus'' H.L. Clark, 1914
* ''Echinarachnius parma parma'' (Lamarck, 1816)
* ''Echinarachnius parma sakkalinensis'' Argamakowa, 1934
Distribution
It is found in the North Pacific and Northwest Atlantic, on the North American east coast from
New Jersey
New Jersey is a U.S. state, state in the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. It is bordered on the north and east by the state of New York (state), New York; on the ea ...
north, as well as in
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S ...
,
Siberia
Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part o ...
,
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost Provinces and territories of Canada, province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include ...
, and Japan. It inhabits isolated areas on sandy bottoms below the low
tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide tables can ...
level down to a depth of .
Description
The tests (shells) of these sand dollars are round, flat and disc-like, typically measuring in diameter. The entire shell is also covered with maroon-colored moveable spines. The color is a purplish brown, becoming bleached white when washed ashore. As in other
echinoderm
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...
s, five radial furrows branch from the mouth on the animal's underside.
This and other species of ''Echinarachnius'' have been around since the
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58''Echinarachnius parma'' Animal Diversity Web