Sea daisies (infraclass Concentricycloidea;
order Peripodida) make up an unusual group of deep-sea taxa belonging to the phylum
Echinodermata
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 ...
, with three
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
described in the genus ''Xyloplax''. Intestine and anus are absent.
Distribution
Sea daisies have been discovered in three localities, including deep-sea habitats off New Zealand, the Bahamas and most recently from the northern central Pacific. They have been collected primarily from sunken, deep-sea (1000+ meters) wood. Although known from only a handful of specimens initially, many specimens have now been collected from the Bahamas.
Classification
Since they were discovered in 1986, their position within the echinoderms has been debated. At first they were placed in a new class, Concentricycloidea, since it was unclear whether they might have affinities with asteroids or ophiuroids. The former view gained acceptance, and since 2006, they are currently considered a sister group to the Infraclass Neoasteroidea, which represents all post-Paleozoic asteroids within the Class
Asteroidea
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish a ...
.
Class Asteroidea,
Infraclass Concentricycloidea,
Order Peripoda (or Peripodida),
Family Xyloplacidae
* Genus ''Xyloplax''
** ''
Xyloplax janetae
''Xyloplax janetae'' is a ''Xyloplax'' of the family Xyloplacidae. It lives on the surface of wood sunken to abyssal depths.
Morphology
''Xyloplax janetae'' is a flattened disk, from in diameter, and about thick. It has adambulacral spines wh ...
''
** ''
Xyloplax medusiformis
''Xyloplax medusiformis'' is a sea daisy, a member of an unusual group of marine taxa belonging to the phylum Echinodermata. It is found at bathyal depths in waters around New Zealand. It was first described in 1986 by Baker, Rowe and Clark and ...
''
** ''
Xyloplax turnerae''
References
Introduction to Xyloplax
{{Taxonbar, from=Q1078908
Peripodida