Lessonothuria, Deichmann, 1958

Ahmed, Quratulan, Thandar, Ahmed S. & Ali, Qadeer Mohammad, 2020, Holothuria (Lessonothuria) insignis Ludwig, 1875 (formally resurrected from synonymy of H. pardalis Selenka, 1867) and Holothuria (Lessonothuria) lineata Ludwig, 1875 - new additions to the sea cucumber fauna of Pakistan, with a key to the subgenus Lessonothuria Deichmann (Echinodermata: Holothuroidea), Zootaxa 4767 (2), pp. 307-318 : 316

Key to the species currently included in the Lessonothuria subgenus

1. Tentacles 20......................................................................................... 4

- Tentacles more than 20................................................................................. 2

2. Tentacles 30; body wall ossicles as in H. pardalis , pseudo-buttons with three pairs of holes, rarely twisted or reduced to a single series holes on one side; single Polian vesicle, multiple stone canals.................... H. (L.) immobilis Semper, 1868 .

- Tentacles 25–30; body wall ossicles as tables and buttons, Polian vesicle and stone canal usually single, well developed.... 3

3. Tentacles 25, Polian vesicle and stone canal usually single; buttons huge with large holes; tables with smooth to spiny disc; spire sometimes with several cross-bars......................................... H. (L.) duoturricola Cherbonnier, 1988 .

- Tentacles 25–30, multiple Polian vesicles and stone canals; tables and buttons well developed, hardly ever reduced................................................................................... H. (L.) verrucosa Selenka, 1867 .

4. Body wall tables apparently flat, rim smooth; some discs multilocular with more than one series of marginal holes, some tables modified to fenestrated spheres and buttons to fenestrated ellipsoids....................... H. (L.) cumulus Clark, 1921.

- Body wall tables and buttons never modified into fenestrated bodies, although a few tables may possess a multilocular disc and a spire made up of several cross-bars...................................................................... 5

5. Buttons mostly complete with two series of holes, not reduced to a single series on one side; tables with multilocular, smooth to spinose, mostly rounded disc; spire often with several cross-bars; plates around end plates serrated............................................................................................... H. (L.) multipilala Liao, 1975.

- Buttons complete or incomplete, holes sometimes reduced to a single series on one side; table disc with 4–8 holes, rim usually spinose, of variable form; some table spires with 1–2 cross bars, or cross bars absent; plates around ventral end plates smooth, serrated or absent..................................................................................... 6

6. Tube feet without suckers, end plates small, no plates surrounding end plates; tables mostly complete with buttons as in H. pardalis but large, up to 100 µm, and with more holes; table disc multilocular, often with more than one series of holes, disc sometimes knobbed or spinose........................................... H (L.) cavans Massin & Tomascik, 1996 .

- Tube feet always with suckers, end plates well developed, nearly always encircled by other often bilaterally symmetrical plates; buttons rarely up to 100 µm and never with more than 3 pairs of holes; table discs never with more than one series of marginal holes............................................................................................... 7

7. Body wall tables of several forms with smooth, undulating rim and low spire with a single cross-bar or rims spinose without a spire or a spire with one or more cross-bars; buttons often complete but twisted or irregularly formed or of bizarre shape...................................................................... Holothuria glandifera Cherbonnier, 1955 .

- Body wall tables always with a spinose margin, spire low or absent, rarely a few tables with multiple cross-bars, buttons regular or incomplete with one or two series of holes............................................................... 8

8. Body covered with distinct tubercles, tables with circular, slightly spinose disc; plates of tube feet irregular, with 1–3 series of holes, never bilaterally symmetrical...................................... Holothuria (L) tuberculata Thandar, 2007.

- Body smooth or rough to the touch, tubercles absent; table disc distinctly spinose; plates surrounding end-plates of tube feet nearly always bilaterally symmetrical with 2 series of holes.................................................... 9

9. Table disc circular, spire low or moderate, ending in about eight teeth, spire rarely absent; buttons accumulated into heaps, complete and incomplete ones in a 50:50 ratio and with three pairs of holes, rarely twisted or reduced to a single series holes on one side; plates surrounding end plates of tube feet with a paired series of holes and usually an undulating margin............................................................................. Holothuria (L.) pardalis Selenka, 1867 .

- Tables with low or reduced spire or spire absent; disc distinctly spinose; ventral buttons mostly reduced, often twisted; dorsal ones complete and incomplete; plates surrounding tube feet end plates either regular with undulating margin or irregular with serrated/spiny/irregular margin.......................................................................... 10

10. Tables with reduced disc, often with only four central holes; spire low or absent, teeth irregular, never consistently eight; buttons mostly incomplete, often twisted, and frequently developed as a single series of three holes; plates associated with endplates bilaterally symmetrical with a series of paired holes and an undulating, rarely serrated rim............................................................................................ Holothuria (L.) insignis Ludwig, 1875 .

- Tables small, disc slightly spinose, pierced by only four holes or also a few small marginal holes; dorsal buttons usually complete, ventral often reduced but not twisted; plates associated with end plates always with serrated/spiny/irregular margin......................................................................... Holothuria (L.) lineata Ludwig, 1875 .