Psolidium Ludwig, 1886

O’Loughlin, P. Mark & Ahearn, Cynthia, 2008, Antarctic and Sub-Antarctic species of Psolidium Ludwig (Echinodermata: Holothuroidea: Psolidae), Memoirs of Museum Victoria 65, pp. 23-42 : 24-25

Key to Antarctic and Sub-Antarctic species of Psolidium Ludwig, 1886

1. Mid-ventral (sole) radial series of tube feet present 2

— Lacking mid-ventral (sole) radial series of tube feet 3

2. Ossicles in sole include irregularly oval to round disc-like smooth plates, variably with few minute, closed to almost closed, perforations

P. disciformis ( Théel, 1886) (S Chile)

— Irregularly oval to round, disc-like smooth plates, variably with few minute, closed to almost closed, perforations, not present in sole

P. dorsipes Ludwig, 1886 (S Chile, S Argentina, Strait of Magellan, Burdwood Bank, Falkland Is)

3. Dorsally with deep goblet-like cups, closed across rim, vertical spines above rim; brood-protects in folds of sole P. incubans Ekman, 1925 ( South Georgia)

— Dorsally lacking deep goblet-like cups closed across rim; no brood-protection in folds of sole 4

4. Dorsal and lateral scales conspicuous; dorsal and lateral tube feet inconspicuous; lacking numerous dorsal and lateral tube feet support ossicles; crosses and small perforated plates rare to absent in sole 5

— Dorsal and lateral scales inconspicuous; dorsal and lateral tube feet numerous and conspicuous; dorsal and lateral tube foot support ossicles numerous; sole with numerous perforated plates 9

5. Largest tentacle trunk ossicles predominantly thick, narrow rod-plates and perforated plates with prominent rod thickenings

P. tenue Mortensen, 1925 (Antarctic Peninsula, Ross Sea, Wilkes Land, Antipodes I., Prydz Bay)

— Largest tentacle trunk ossicles predominantly smooth perforated plates 6

6. Dorsal scales frequently with well-developed, radiating-to-margin, linear, rounded thickenings between rows of marginal perforations

P. poriferum ( Studer, 1876) (Marion, Kerguelen, Heard, McDonald Is; MacRobertson Land)

— Dorsal scales rarely with linear thickenings between rows of marginal perforations 7

7. Dorsal scales frequently with smooth white thickening; perforations reduced, many almost closed

P. pawsoni sp. nov. (Weddell Sea, Ross Sea, Enderby Land)

— Dorsal scales with irregular lumpy or reticulate thickening, rarely with smooth white thickening and almost closed perforations 8

8. Largest tentacle trunk ossicles predominantly plates with large irregular perforations

P. whittakeri sp. nov. (South Sandwich, Bouvet, South Shetland Islands)

— Largest tentacle trunk ossicles predominantly plates with large perforations centrally grading to numerous small close perforations marginally

P. schnabelae sp. nov. (off Prydz Bay, MacRobertson Land)

9. Ossicles in sole numerous crosses; rare perforated plates P. emilyae sp. nov. (Prydz Bay)

— Ossicles in sole perforated plates 10

10. Dorsal scales single-layered only perforated plates; perforated plates in sole lacking irregular thickenings

P. gaini Vaney, 1914 ( South Georgia, S Orkney Is, Weddell Sea, Antarctic Peninsula, Ross Sea, Prydz Bay)

— Dorsal scales single-layered with some secondary layering; sole with irregularly thickened, scale-like perforated plates

P. normani sp. nov. (Adelie Land, Prydz Bay, MacRobertson Shelf, Enderby Land)