Pillsburiaster aoteanus McKnight, 1973

Pillsburiaster aoteanus McKnight, 1973 View in CoL

Figures 16A–E

Pillsburiaster aoteanus McKnight, 1973: 180 View in CoL , fig. 5; A.M. Clark, 1993: 276; H.E.S. Clark and McKnight, 2001:100, Pl. 27; Mah, 2011: 39; MacIntosh et al., 2018: 12.

Plinthaster singletoni McKnight, 1973: 185 View in CoL , fig. 7; 1993: 169; A.M. Clark, 1993: 277.

Material Examined. NMV F123060 About NMV . Lord Howe plateau, site 10, Tasman Sea , 34° 2' 24.7194" S, 163° 17' 13.2" E, 1976– 1083 m. Coll. TAN 0308 091, 26 May 2003. 2 wet specs GoogleMaps . R = 3.8 r = 2.3 R = 5.1 r = 2.7

NMV F246909 About NMV . St. Helens flat, Tasmanian Seamounts , 41° 12' 15.48" S, 148° 47' 16.8" E, 1202–1221 m. Coll. Dr A.Williams GoogleMaps - CSIRO, Dr. Alexandra A. Weber - Museums Victoria, Ricky-Lee Erickson - Museums Victoria, et al, 17 December 2018. 1 wet spec . R = 3.4 r = 1.7

NMV F123058 About NMV . Wanganella Bank, site 13, 34° 4' 59.5194" S, 168° 55' 33.5994" E, 1000–1150 m, Coll. 6 March 2003, 1 wet specimen GoogleMaps .

NMV F123071 About NMV . Lord Howe Plateau, Tasman Sea , 32° 39' 20.1594" S, 162° 33' 7.1994" E, 864–870 m. Coll. M.F. Gomon, Museum Victoria, NORFANZ team, 25 May 2003, 1 wet specimen GoogleMaps .

NMV F122953 About NMV . Wanganella Bank, site 13, 33° 2' 26.8794" S, 167° 27' 3.5994" E, 1451–1478 m, Coll. 28 May 2003, 3 wet specs GoogleMaps .

NMV F240377 About NMV . Great Australian Bight , South Australia, 34° 36' 32.7594" S, 131° 3' 21.6"E, 1478–1507 m. Coll. Great Australian Bight, BP Expedition. 12 September 2015. 1 wet spec GoogleMaps .

NMV F240378 About NMV . Great Australian Bight , South Australia, 33° 55' 41.88" S, 131° 3' 39.6" E, 1021–1033 m, Coll. Great Australian Bight, BP Expedition. 12 September 2015. 1 wet spec GoogleMaps .

NMV F240380 About NMV . Great Australian Bight , South Australia, 33° 30' 57.96" S, 130° 15' 53.9994" E 978–1013 m, Coll. Great Australian Bight, BP Expedition. 12 September 2015. 1 wet spec GoogleMaps .

NMV F240381 About NMV . Great Australian Bight , South Australia, 34° 31' 49.44" S, 130° 40' 8.4" E, 1473–1483 m, Coll. Great Australian Bight, BP Expedition. 12 September 2015. 1 wet spec GoogleMaps .

USNM 1098141 About USNM . Cook Strait , New Zealand, South Pacific Ocean, 41° 42' 0" S, 175° 25' 30" E, 946– 951 m. Coll GoogleMaps . R / V Eltanin, US Antarctic Research Program 31 January 1965. 1 dry spec . R = 2.2 r = 1.3.

USNM 1100862 About USNM . Campbell Plateau New Zealand, South Pacific Ocean - 48° 40' 0.1194" S, 170° 48' 28.7994" E, 814 m. Coll. 20 Jan 1965. 2 dry specs GoogleMaps . R = 5.8 r = 3.6; R = 3.3 r = 2.3.

USNM 1100852 About USNM . Campbell Plateau New Zealand, South Pacific Ocean 49° 13' 30" S, 171° 30' 7.2" E, 260 m. Coll. 21 Dec. 1970, 1 dry spec GoogleMaps ., R = 6.5 r = 3.8.

Diagnosis (Modified from McKnight, 1973). Body pentagonal (R/r = 1.4–2.0), interradial arcs weakly curved to straight. Abactinal plates with large, round spherical granules, 7–20 (at R = 6.5). Marginal plates 18 (R = 2.0) to 30 (at R = 6.5) per interradius, arm tip to arm tip. Superomarginal surface covered by granules save for a small bald area present centrally on dorsal surface. Furrow spines 5 to 7, flat tipped, blunt, quadrate in cross-section. Subambulacral spines short, 4 to 6, blunt, granular in 2 to 3 irregular series, set off from furrow spines by distinct diastema. Pedicellariae present or absent.

Comments. Descriptions for P. aoteanus presented in McKnight (1973) and H.E.S. Clark and McKnight (2001) differed in several respects from other specimens of P. aoteanus in the USNM collections. These include differing counts of the abactinal granules, showing a greater range than indicated in earlier description and an accounting of superomarginal plates, up to 32 per interradius at R = 6.5 (USNM 1100852) which specifically differs from the description in Clark and McKnight (2001) which describes the species as showing 18 (possibly 20 in their plate 27) platesperinterradiusonaspecimenatR= 6.0.Thesuperomarginal plate and abactinal granule number are significant because these are used by McKnight to distinguish P. aoteanus from P. maini . These values show overlap suggesting that the two species are nearly indistinguishable, differing only in that P. maini shows a distinct “substellate” body shape (R/r = 2.7).

The Australian specimens are consistent with characters of P. aoteanus as outlined herein and in Clark and McKnight (2001) but show a much larger more distinct quadrate to round bald patch rather than the small, irregular patch on the dorsal surface of each superomarginal plate. Furrow spine number and adambulacral spination are consistent.

Aside from the presence of Pillsburiaster sp. in MacIntosh et al. (2018) from the Great Australian Bight these are the first published occurrence of Pillsburiaster in Australian and nearby waters.

Occurrence/Distribution. New Zealand area. Near Three Kings Rise, north of North Cape , New Zealand and from Hawkes Bay to south of Campbell Island , east to near Chatham Islands, 120–1573 m .

Australia. Tasmanian seamounts, Great Australian Bight. 1083–1507 m.

Description. Body weakly stellate to stellate, R:r = 1.6:2.0, arms broad at base, triangular. Interradial arcs weakly curved to straight ( Fig. 16A, D).

Abactinal plates round to polygonal, surface of each plate with coarse, round granules, 2 to 20, mostly 15 to 15, homogeneous in size, shape ( Fig. 16A, B, C). Densest aggregations distally adjacent to contact with superomarginal plates. At smaller sizes, R= 3.4, minority of distal interradial plates with bare central region. Papular regions extensive, ranging from central disk to approximately six superomarginals from terminus; individual pores single. Madreporite pentagonal, flanked by 6 plates. No pedicellariae observed.

Superomarginal plates 12 per side, 24 from arm tip to arm tip (at R=3.4 to 5.1) with rounded dorsolateral edge ( Fig. 16A, C). Abactinal surface of each plate with variably sized, irregular round bald spot on dorsal to dorsolateral surface, occupying central plate surface ( Fig. 16C). Remainder of superomarginal plate covered by granules, round, deciduous, approximately 100–300, forming abundant covering on lateral surface of superomarginal plate. Inferomarginal covered by granules, round, coarse, closely but evenly arranged. No pedicellariae. Terminal plates triangular, lacking granulation. No pedicellariae.

Actinal plate region in approximately 4 complete series in chevron-like formation. Each plate quadrate to irregularly polygonal, covered by granules, 5 to 50, evenly arranged ( Fig. 16D, E). No pedicellariae.

Furrow spines 4 to 6, blunt, weakly clavate, in straight to weakly palmate arrangement on plate ( Fig. 16E). Furrow spines set off from subambulacral granules by distinct diastema. Subambulacrals in approximately 3 irregular series, each composed of 2 to 5, mostly 3 or 4 blunt granules. Adambulacral accessories similar to actinal granules in overall appearance but set off by a weakly developed groove. Oral plates with furrow spines, approximately 12 with a single prominent blunt spine directed into the mouth on each plate, totalling 2 per interradius. Oral plate surface with approximately 12 paired granules on either side of central diastema. Both sides of oral plate surface covered by approximately 15–20 granules arranged in two series parallel to the central diastema.