Tethisea alanwilliamsi, Poore And D, 2015

Poore And D, Gary C. B., 2015, Micheleidae (Crustacea: Decapoda: Axiidea): new family, generic and species synonymies, three new Australian species, and new records, Memoirs of Museum Victoria 73, pp. 95-105 : 102

Tethisea alanwilliamsi sp. nov.

Figures 3, 4

Tethisea sp. MoV5472.— Poore et al., 2008: 95.

Material examined. Holotype. Western Australia, off Pt Hillier (35°22.53'S – 35°22.56'S, 117°12.11'E – 117°11.31'E), 419–460 m, 22 Nov 2005 (stn SS10/2005/096), NMV J55604 (male, cl 9.7 mm).

Diagnosis. Rostrum with convex lateral margins meeting at subacute tip. Maxilliped 3 without exopod. Cheliped without strong spiniform setae in gape; fingers moderatly stout, not finely attenuating. Uropodal exopod 1.3 times as long as wide.

Description. Cephalothorax 0.35 total length, about 1.1 times as deep as wide; rostrum with convex lateral margins, obscuring eyes from dorsal view, meeting at subacute tip, slightly depressed distally, with dorsal setae along lateral carinae, 1.6 times as long as broad at base of eyes, almost 3 times as long as eyestalks; lateral carinae extending on to cephalothorax, without median carina; cervical groove weakly defined; dorsoposterior margin a convex medial lobe, separated from posterolateral margins; without setal-row.

Pleomere 1 narrower than pleomere 2, with anterolateral lobes overlying posterolateral margins of cephalothorax; pleuron without marginal spine; dorsolateral setal-row of 7 setae. Pleomere 2 1.5 times as long as first, pleuron broadly overlapping first somite. Pleomeres 2–5 without setal-rows. Pleomere 6 with longitudinal setal-row of about 10 setae.

Eyestalks acute distally, cornea pale, distal.

Antennule with article 1 shorter than rostrum; articles 2 and 3 subequal, each about 0.4 length of article 1; flagella each of c. 14 articles, longer than peduncle. Antenna with long acute articulating scaphocerite, 0.85 length of article 4; article 4 reaching to near end of article 3 of antenna 1; article 5 short.

Mandible, maxillae, maxillipeds 1 and 2 typical of genus. Maxilliped 3 ischium with crista dentata of 7 blunt teeth; merus without mesial tooth; ischium-merus with dense mesial rows of long setae; carpus–dactylus longer than ischium–merus; exopod almost semicircular, length about half width of ischium.

Chelipeds equal in size but with slight variation in spination; ischium with distal spine on lower margin; merus with 3 (right) and 2 (left) spines on lower margin, upper margin strongly convex; carpus unarmed, carinate on upper margin; propodus 2.8 times as long as deep, deepest at midpoint, with carinate upper and lower margins, almost folded over on upper; fixed finger 0.3 length of propodus, with proximal blunt tooth on cutting edge, more prominent on left; gape slight, without long spiniform setae laterally; dactylus cutting edge concave proximally, blunt. Pereopod 2 merus–propodus with lower marginal rows of long setae; carpus 0.6 length of merus; propodus as long as carpus, without setal-row; fixed finger cutting edge with numerous contiguous spiniform setae; dactylus longer than fixed finger, straight. Pereopod 3 propodus 1.3 times as long as wide, upper and lower margins convex, posterior face densely setose, the whole forming a shallow oval dish-like surface, without setal-row; dactylus broad. Pereopod 4 propodus 1.8 times as long as wide, without setal-row; dactylus broad. Pereopod 5 propodus with short fixed finger; dactylus curved, about 3 times as long as fixed finger, distally rounded.

Pleopods 1 of male 2-articled, second article 4 times as long as wide, with medial lobe bearing minute hooks. Pleopod 2 missing. Pleopod 3 endopod 3.8 times as long as wide; appendix interna 10 times as long as wide; exopod twice as long as wide, ovate. Pleopods 4 and 5 essentially similar to pleopod 3.

Uropodal endopod with anterior margin weakly convex, ending by curving to rounded posterior margin, 1.3 times as long as wide; exopod with shallow concave anterior margin, apically rounded, posterior margin broadly lobed, 1.3 times as long as wide; with uneven robust setae among many plumose setae. Telson 1.1 times as long as wide, tapering to truncate apex beyond constriction one-third way along.

Distribution. Western Australia, 35°S, 117°'E, 419– 460 m.

Etymology. For Alan Williams, CSIRO Marine Laboratories, Hobart, promoter and organiser of the much-appreciated Voyages of Discovery research program, especially in Western Australia.

Remarks. Tethisea alanwilliamsi differs from T. indica Poore, 1994 and T. mindoro Poore, 1997 in the absence of strong spiniform setae in the gape of the cheliped. The outline of the rostrum in dorsal view is intermediate between that of the described species; the cheliped is more robust and its fingers not of their attenuating acute form.