Mediaster aequalis Stimpson 1857

Mah, Christopher L., 2016, Deep-sea (> 1000 m) Goniasteridae (Valvatida; Asteroidea) from the North Pacific, including an overview of Sibogaster, Bathyceramaster n. gen. and three new species, Zootaxa 4175 (2), pp. 101-141 : 119-120

Mediaster aequalis Stimpson 1857

Stimpson 1857: 530; Fisher 1911: 198; Ziesenhenne 1937: 214; Alton 1966a: 1682, 1701; Blake 1973: 49; Kozloff 1987: 449, 450, 453 (key & checklist); Maluf 1988: 34, 118; A.M. Clark 1993: 262; Lambert 2000: 57, 67; Lamb & Hanby 2005:327; Mah 2007b: 927(in key) (as Mediaster aequalis )

Dujardin & Hupé 1862: 365 (as Ophidiaster )

Occurrence. Alaska / Aleutian Islands , British Columbia , Washington , Oregon , California (including Cordell Bank) to Southern California and Gulf of California (Cortez Seamount), intertidal to 1500 m .

Comments. Although three specimen lots are outlined below, they all represent sampling from one locality. This record of this primarily shallow-water species below 1000 m suggests that it is the lower limit of this species’ distribution. The largest of those sampled had an R=2.6 with only three furrow spines. Larger, shallower individuals display up to five furrow spines. Pedicellariae were not observed on these smaller individuals (R<2.0) which also display three furrow spines. These specimens also showed a more weakly stellate body form (R=~1.8) versus the R/r=2.6 as outlined by Fisher (1911).

One specimen of Mediaster aequalis collected from Cortez Bank in the Gulf of California from 91.4 m showed a stellate body from (R/r=2.3) but with sharply triangular arms, four furrow spines (at R=2.8), and a strongly expressed superomarginal plate series which occupies approximately 28% of the distance r (disk center to edge of interradius) whereas more northern individuals display superomarginals which occupy only 14% of the distance r.

Material examined. CASIZ 117511, 2–3 nautical miles SW of Pt. Soberantes, Monterey County, California. 36º25’7N, 120º58’20”W, 1280–1500 m (700–820 fms). Coll. R / V Searcher. 7 wet spec. R=1.6, r=0.8; R=1.1, r=0.6; R=1.2; r=0.6; R=1.7, r=0.8; R=1.4, r=0.7; R=1.8, r=0.9; R=2.6, r=1.4 . CASIZ 117603, 2–3 nautical miles SW of Pt. Soberantes, Monterey County, California. 36º25’7N, 120º58’20”W, 1280–1500 m (700–820 fms). Coll. R / V Searcher. 1 wet spec. R=1.0, =0.5 . CASIZ 115535, 2–3 nautical miles SW of Pt. Soberantes, Monterey County, California. 36º25’7N, 120º58’20”W, 1280–1500 m (700–820 fms). Coll. R / V Searcher. 1 wet spec. R=1.1, =0.6.

Gulf of California. CASIZ 117620 Cortez Bank 32º34’N, 119º16’W, 91.4 m (50 fms). Coll. Crocker-Stanford Deep-Sea Expedition, R / V Zaca. 1 wet spec. R=2.8, r=1.2.