Paralophaster antarcticus (Koehler, 1912a)

FIGURE 18A–F

Lophaster antarcticus Koehler, 1912a: 46 .

Myoraster antarcticus Fisher 1940: 181; H.E.S. Clark 1963: 56 (synonym according to A.M. Clark 1962: 52).

Paralophaster antarcticus A.M. Clark 1962: 52 .

Solaster incertus Koehler, 1917: 40 .

Paralophaster incertus A.M. Clark 1962: 50 .

Diagnosis

Body stellate R/r= 2.5–4.0.Abactinal surface paxillate, each bearing 30–40 hyaline spinelets that forms a dense, canopy-like covering over surface, appearing “fuzzy” (Fig. 18A, B, D). Superomarginals with paxillae bearing dense spinelets, 20–40 (at R=13.0 cm), adjacent to inferomarginals, approximately twice the size of adjacent abactinal paxillae (Fig. 18D). Inferomarginal paxillae prominent, large 2 to 3 times the size of the superomarginals with elongate tips, 40–80, 40 per interradius, 20 per arm at R=2.0 cm, 60–80 at R=20.0 cm per interradius, 30–40 along each arm. Each paxilla with dense, numerous spinelets, 30–40. Furrow spines 4, then 3 along most of arm. Subambulacral spines 3 to 5, unwebbed (Fig. 18F).

Comments

Fisher’s (1940) most seemingly relevant character for Myoraster (= Paralophaster antarcticus) was the presence of a longitudinal muscle band lying between the adambulacral and superomarginal plates and extending from the end of the ray to the interbrachial angle. A.M. Clark (1962) identified this muscle band in Lophaster antarcticus as well as Paralophaster godfroyi . The extent to which this character is functionally important is unclear, but ultimately A.M. Clark (1962: 52) did not find them to be of “generic importance” and synonymized Myoraster with Paralophaster .

Gut contents of CASIZ 174645 contained disarticulated comatulid crinoid ossicles, which were identified as belonging to Florometra mawsoni, based on the presence of short spinelets around the edge of the columns.

One specimen, among USNM 1418098 had six arms rather than the five present in most other specimens.

What is Paralophaster incertus ?

While reviewing the high-latitude Paralophaster, inconsistencies emerged for Paralophaster incertus, described as Solaster incertus Koehler, 1917 from Kerguelen Island. Fisher (1940) did not accept S. incertus as Paralophaster . A.M. Clark (1962) included Paralophaster incertus in her key to Paralophaster with no comment but did not include this species under Paralophaster among her listing of asteroid names (A.M. Clark 1997).

An image of the holotype (MNHN IE-2014-95) as well as images and the description from Koehler (1917) suggest that this either shows close affinities with or is a synonym of Paralophaster antarcticus . Koehler’s description alludes to the poor condition of the holotype which obscured more precise descriptions of this species. However, it shows approximately 29 to 30 inferomarginal plates, as well as the dense, close-set paxillar pattern of the spinelets on the abactinal plates. Specimens of Paralophaster antarcticus (e.g., USNM E13466) with comparable size (R= 1.7 to 2.3 cm to versus the type at R= 1.5 cm) had a similar appearance to Paralophaster incertus with comparable numbers of marginal plates along the arm (n=22 at R= 1.7 cm to 26 at R= 2.2 cm) with superomarginals intercalated between the inferomarginals. The oral surface figured by Koehler (1917) also displays characters consistent with P. antarcticus, such as 4 to 5 subambulacral spines. Thus, Paralophaster incertus is a junior synonym of Paralophaster antarcticus (Koehler, 1912a) .

Occurrence

South Georgia and South Sandwich Islands, Palmer Archipelago. Bellinghausen Sea. Adelie Land, Ross Sea. South Atlantic, Bouvet Island, Tierra del Fuego. 99–746 m.

Material Examined

USNM E13473, South of Clarence Island South Shetland Islands, Southern Ocean. −62.18, −57.825, 746 m. Coll. R/V Eastwind, 19 Feb. 1966. 1 dry spec. R=8.5 r=2.1.

USNM E38487, South Georgia, South Atlantic, −53.67, −36.8, 161–192 m. Coll. USAP, R/V Siedlecki. 1 dry spec. R=13.0 r=4.0.

USNM E47668, Saunders Island, South Sandwich Islands, Scotia Sea. −57.69, −26.3717, 355–468 m. Coll. R/V Islas Orcadas, USAP, 26 May 1975. 3 dry specs. R=12.6 r=3.6, R=16.3 r=3.6, R=13.2 r=4.2.

USNM E53425, Melchior Island, Dallmann Bay, Palmer Archipelago, Antarctic Peninsula, Southern Ocean. −64.3129, −62.9722, 85–130 m. Coll. R/V Hero, USAP, 22 March 1982. 1 dry spec. R=6.3 r=2.2.

USNM 1110074, Bouvet Island, South Atlantic Island, −54.3482, −3.3765, 200 m. Coll. S. Kim, Moss Landing Marine Labs. 1 wet spec.

USNM 1120489, Victoria Land, Ross Sea, Antarctica. −71.367, 170.683, 160–164 m. Coll. R/V Eltanin, USAP. 10 dry specs. R=2.2 r=0.7, R=2.5 r=0.8, R=2.2 r=0.8, R=1.9 r=0.6, R=2.1 r=0.6, R=1.8 r=0.8, R=2.0 r=0.8, R=2.0 r=0.8, R=1.4 r=0.5, R=1.1 r=0.3.

USNM 1130751, Staten Island, Puerto Roca, Tierra del Fuego, South Atlantic. −54.7308, −64.2267, 712 m. Coll. R/V Hero. 1 dry spec.

USNM 1418098, Cape Hallett, Moubray Bay, Victoria Land, Ross Sea, Southern Ocean, Antarctica, −72.308, 170.425, 143−146 m. Coll. R/V Eltanin, 15 Jan. 1967. 7 dry specs. R=6.5 r=1.7, R=4.7 r=1.4 R=3.6 r=1.1, R=2.5 r=0.8 R=2.7 r=1.0 (six arms), R=2.8 r=0.9 (with molt in gut), R=3.7 r=1.0.

USNM 1136644, Antarctic Peninsula, Southern Ocean, Antarctica, −62.683, −54.717, 210–220 m. Coll. R/V Eltanin, 15 March 1964. 4 dry specs. R=~12.0 r=3.3, R=7.7 r=2.1, R=10.3 r=2.5 (specimen fragmented), R=10.7 r=3.5 (with crinoid ossicles in gut).

USNM 1676717, Victoria Land, Ross Sea, Southern Ocean, Antarctica. −72.008, 172.508, 523−528 m. Coll. R/V Eltanin, 10 Jan. 1968. 5 dry specs. R=2.8 r=0.9, R=1.1 r=0.4, R=0.9 r=0.3. R=1.1 r=0.4, R=0.5 r=0.2.

CASIZ 174645, Bouvetoya, South Atlantic, −54.4903333, −3.2383333, 166−172 m. Coll. Lockhart & Mooi aboard R /V Nathaniel B. Palmer, 30 June 2004. 1 wet spec. R=3.1 r=1.0 (with gut contents) .