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The Forcipulatacea is a diverse, primarily cold-water (some temperate and tropical members are known) lineage of modern asteroids that occur in all of the world's oceans from the intertidal to the deepest abyssal depths (>6000 m). The Forcipulatacea includes 393 species in 77 genera (Mah 2012), which ranks them as among the most diverse of the Asteroidea. Forcipulataceans are most diverse at high-latitudes with rich faunas in the Arctic and especially in the Antarctic.
Although the Forcipulatacea display a wide range of morphologies, taxonomists traditionally have found them to be readily separated from the remainder of the crown group. Characters helping to characterize forcipulataceans but not found in all members include the presence of distinct 3-part “forcipulate” pedicellariae (although pedicellariae vary among taxa), four rows of tube feet; foreshortened (or “compressed”) ambulacral and adambulacral ossicles, the latter alternating in furrow profile in taxa with four rows of tube feet; a reticulated dorsal skeleton; a well-developed adoral carina (abutted adambulacral plates adjacent to the mouth, the proximal skeleton recessed to form a so-called actinostome); small mouth-angle ossicles; the longest actinal series adjacent to the marginals rather than adjacent to the adambulacrals; and a small disk with thick, tapering arms.
Most historical accounts (Spencer and Wright 1966, Fisher 1911) have set apart the Forcipulatacea or “forcipulate” asteroids (i.e., the Forcipulatida+Brisingida) from the other members of the Asteroidea. This is a position that has been further supported by modern phylogenetic treatments of morphology (Blake 1987; 1990; Janies et al 2011; Matsubara et al 2005 and this study). Gale (2011) has placed forcipulates in a derived position within taxa historically regarded as members of the Valvatida. This position has not found historical agreement and is not followed by the treatment herein.
Monophyly of the Forcipulatacea itself has been relatively uncontroversial with support from traditional taxonomy (Fisher 1928, 1930), morphology-based phylogenetic studies (Blake 1987; Gale 1987) and molecules (Janies et al 2011; Matsubara et al 2005, Matsubara et al. 2004, Foltz et al. 2007; Mah and Foltz 2011). Subgroupings within the Forcipulatacea have encountered more difficulty, especially those associated with the Asteriidae, such as the Labidiasteridae (Fisher 1930; Spencer and Writght 1966; Fisher 1928; Mah 2000). Mah and Foltz (2011) provided the taxonomic foundation for the summary below.
The Forcipulatacea, particularly the Asteriidae includes some of the most heavily studied and most familiar of marine invertebrates in ecology and environmental biology. Relevant taxa include Pisaster ochraceus, which has become an iconic representative of the keystone species concept as outlined by Paine (1966, 1969, 1974) and Asterias amurensis, which has been introduced to southern Australia as a pest species that threatens endemic shellfish (Ross, Johnson, Hewitt 2002, 2003, 2006; Ross, Johnson, Hewitt, Ruiz 2004). The Atlantic Asterias rubens and Asterias forbesi have been among the most familiar of ecological subjects in marine biology studies (Gaymer et al. 2001; Wong and Barbeau 2005). As important ecological members, asteriids such as the European Asterias rubens, the North Pacific Evasterias troscheli, and the temperate South Pacific Coscinasterias muricata have also been used as subjects in several oil pollution studies (O'Clair and Rice 1985; Georgiades et al. 2006; Joly-Turquin et al. 2009, respectively).
Taken from Mah and Blake 2012.