Evoplosoma Fisher 1906

Mah, Christopher L., 2024, Two New Taxa of Goniasteridae (Asteroidea, Echinodermata) and Noteworthy Observations of Deep-Sea Asteroidea by the NOAA Ship Okeanos Explorer in the North and Tropical Atlantic, Zootaxa 5432 (4), pp. 461-508 : 486

Evoplosoma Fisher 1906

Fisher 1906: 1065; Koehler 1909: 96; Spencer & Wright 1966: U58; Clark & Downey 1992: 241; A.M. Clark 1993: 253; Mah et al., 2010: 278; Mah 2015: 2; 2022: 42

Diagnosis

Body strongly stellate. Arm narrow, elongate. R/r ranges from 2.3–4.11 (most between 3.0–4.0). Interradial arcs straight to weakly curved. Abactinal plates, flat and platform-like. Carinal series poorly distinguished. Abactinal plates tightly articulated. Body covered by tissue layer with pulpy texture that overlies plates and spines (seen more clearly in wet specimens). Prominent spines on abactinal, superomarginal, inferomarginal and actinal plates in most species. Spine morphology variable from blunt conical to pointed, to cylindrical or small and spinelet-like. Granules with spiny tips in most s pecies, with some having rounded surfaces. Granules present but with variable abundance among species. Tong-like pedicellariae with serrated valves present or absent on abactinal, marginal or actinal surface. Marginal plates generally quadrate in shape, some showing direct 1:1 superomarginal/inferomarginal correspondence but others being more offset. Marginals relatively numerous ranging in number from 30–70 per interradius. Some species with bare marginal plate surface, but most with even to dense granule covering. Granules varying from having rounded surface to pointed or prismatic edges. Large prominent spine or spines known in all but one species. Large single spines observed as a linear series in several species. Spinelets or multiple shorter spines observed on marginal plate surfaces of other species. Pedicellariae variably present on either supero or inferomarginal series. Actinal intermediate regions relatively small with fewer than six rows present (three or four present in most species).Actinal plate boundaries obscured by pulpy tissue layer and/or granulation. Granules round or with spiny edges present on all species. Primary spines present on actinal plate surface in most species. Furrow spines varying in number from 2–3, to 7–12. Spines generally compressed, quadrate to polygonal in cross section. Tips varying from smooth and blunt to jagged with furrowed tips. Subambulacral spination variable but a felipedal (clamp-like bivalve) pedicellariae present among the subambulacrals in most species. Subambulacrals varying but spination ranging from blunt spines, pointed spinelets to pointed or rounded granules.

Based on in situ observations herein and from prior accounts (e.g. Mah et al. 2010), the color of most species ranges from yellow to deep orange.

Modified from Mah (2015).

Comments

A total of 11 species of Evoplosoma are known, four of which are known only from the Atlantic, including Evoplosoma scorpio Downey 1981 , Evoplosoma virgo Downey 1982 , Evoplosoma watlingi Mah 2015 and Evoplosoma nizinskiae Mah 2020 . Most observations and records of Evoplosoma were made from the western and tropical Atlantic with only Evoplosoma scorpio recorded from the western and eastern Atlantic.

Image Observed

Kurchatov Ridge, North Atlantic, 40.662611 -29.385243, 1725 m. EX2205_IMG_20220725T134301Z_ROVHD.jpg