''Eucidaris'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of cidaroid

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) ...

s known as slate pencil urchins. They are characterised by a moderately thick

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

, a usually monocyclic apical disc, perforate and non-crenulate tubercles and nearly straight

ambulacra Ambulacrum is an architectural word that denotes an atrium, courtyard, or parvise in front of a basilica or church that is surrounded by arcades or colonnades, or trees, and which often contains a fountain A fountain, from the Latin "fo ...

with horizontal pore pairs. The primary spines are few and widely spaced, stout with blunt flat tips and beaded ornamentation and the secondary spines are short and apressed. They originated in the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

and

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

members of the genus are found in the tropical

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

Ocean, East Pacific, Atlantic Ocean and

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

Species

The World Register of Marine Species lists the following species: * '' Eucidaris australiae'' Mortensen, 1950 * † '' Eucidaris coralloides'' Fell, 1954 * ''

Eucidaris galapagensis ''Eucidaris galapagensis,'' commonly referred to as the slate pencil sea urchin, is a species of echinoderms in the family of Cidaroid. This sea urchin lives in coastal areas in the Galapagos, Clipperton, and Cocos. The preferred substrate of ...

'' Döderlein, 1887 * '' Eucidaris metularia'' (

Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist, biologist, academic, and soldier. He was an early proponent of the idea that biolog ...

, 1816) * † '' Eucidaris strobilata'' Fell, 1954 * ''

Eucidaris thouarsii ''Eucidaris thouarsii'', the slate pencil urchin, is a species of cidaroid sea urchins that inhabits littoral regions of the East Pacific Ocean. Distribution and habitat ''Eucidaris thouarsii'' is found in the East Pacific at depths of , rangi ...

'' (

Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he re ...

& Desor, 1846) * ''

Eucidaris tribuloides ''Eucidaris tribuloides'', the slate pencil urchin, is a species of cidaroid sea urchins that inhabits littoral regions of the Atlantic Ocean. As a member of the basal echinoid order Cidaroida, its morphological, developmental and molecular ge ...

'' (

, 1816) ;Species brought into synonymy: * ''Eucidaris clavata'' Mortensen, 1928: synonym of ''Eucidaris tribuloides'' (Lamarck, 1816) Eucidaris metularia.jpg, '' Eucidaris metularia'' Eucidaris Baltimore Aquarium.jpg, ''

'' Cidaroid urchin in Galapagos.jpg, ''

References

Pomel, A. 1883. Classification méthodique et Genera des Échinides vivantes et fossiles. Thèses présentées à la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles 503, Adolphe Jourdan, Alger, 131 pp
{{Taxonbar, from=Q3458737 Cidaridae Cidaroida genera