Mediaster praestans Livingstone, 1933

Mediaster praestans Livingstone, 1933 View in CoL .

Figure 13 A–F

Livingstone 1933: 21; H.L. Clark 1946: 83.

Material Examined. NMV F270807 About NMV . Baseline 14, Tasmanian seamounts, Tasmania, Australia. 44º 6' 22" S, 146º 12' 13" E, 940–965 m. Coll. A. Williams, A. A. Weber, and R-L. Erickson, 6 December 2018 GoogleMaps , CSIRO. 1 wet spec. R = 2.0 r = 1.0.

Diagnosis. Number of abactinal plate rows decreasing along arm, becoming single series adjacent to arm tip. Each tabula with 10 peripheral granules, 2 to 4 centrally. Holotype with central granules 2 to 6, peripheral angular granules, 6 to 17. Marginal plates 30 per interradius, arm tip to arm tip (15 along each arm), wide, encroaching onto abactinal region. Surface covered by granules, when removed leaving numerous convex bosses. Adambulacral plates with blunt quadrate furrow spines, 7, subambulacral spines in two series, each composed of 3 blunt spines. Subambulacrals shorter adjacent to contact with actinal plates. Pedicellariae absent from all surfaces.

Comments. Characters on this specimen identify it as M. praestans Livingstone 1933 . This includes identical abactinal tabulae and adambulacral spination, similar arrangement of abactinal disk plates, and marginal plate morphology. Pedicellariae are absent. The holotype displays a more stellate shape, R /r = 2.5 versus 2.0 in the current specimen but otherwise appears consistent .

This represents the first account of this species since its description, from the northeast coast of Queensland. The holotype did not have a recorded depth, making this specimen the first to show bathymetric occurrence. Its depth, 940–965 m suggests that this species is present in deep-sea settings. This specimen was collected from Tasmanian seamounts, significantly south of the type locality off Queensland suggesting that Mediaster praestans is a widely occurring species .

Occurrence/Distribution. NE coast of Queensland, no depth information.

Tasmanian Seamounts, 940–965 m.