Trypaea Dana, 1852

Poore, Gary C. B., Dworschak, Peter C., Robles, Rafael, Mantelatto, Fernando L. & Felder, Darryl L., 2019, A new classification of Callianassidae and related families (Crustacea: Decapoda: Axiidea) derived from a molecular phylogeny with morphological support, Memoirs of Museum Victoria (Mem. Mus. Vic.) 78, pp. 73-146 : 100

Trypaea Dana, 1852

Trypaea Dana, 1852a: 14 .— Poore, 2004: 184.— Sakai, 2011: 385– 387 (partim).

Callianassa (Trypaea) .— Borradaile, 1903: 546.—De Man, 1928: 27, 96 (partim).

Type species. Trypaea australiensis Dana, 1852 , by monotypy.

Diagnosis. Rostrum obsolete or obtusely triangular, flat, not reaching cornea. Pleomere 1 tergite undivided or with weak transverse step. Eyestalk distal lobes obsolete, truncate. Antennular peduncle length about 4 times the width of both eyestalks, twice as long as antennal peduncle; articles 2 and 3 with 2 single similar rows of closely spaced setae laterally and mesially along lower margin, extending on to flagellum. Maxilliped 3 merus grossly expanded distomesially beyond articulation with ischium, wider at ischium-merus suture than long; crista dentata absent (or few proximal spines only). Male major cheliped merus with prominent truncate hook armed with serrations along lower margin, excavate laterally at base; carpus and propodus flattened, upper and lower margins carinate, blade-like, submarginal mesial face especially of carpus deeply concave; propodus distal margin with deep notch at base of fixed finger. Pereopod 3 propodus rectangular, lower margin deeply convex, leading to broadly rounded free proximal lobe. Male pleopod 2 absent. Uropodal endopod ovoid, usually longer than wide, anterior margin straight or slightly convex, posterodistal margin evenly convex, with facial distal transverse row of short spiniform setae. Telson lateral margins convex; slightly concave, sometimes with medial spine.

Remarks. Trypaea australiensis is immediately distinguished from all other callianassids by the massive antennular peduncles, far exceeding the antennal peduncles, bearing on their lower margin a double row of adjacent long setae. The merus of maxilliped 3 is more grossly expanded distally than in any other genus. In all other genera that appear to have setose antennae, the setae are scattered in broad bands and not adjacent. Trypaea has only one species which is genetically well separated from its sister taxa (Robles et al. 2019). These are Arenallianassa from south-east Australia, Filhollianassa from south-east Australia and New Zealand, and the more widespread Indo-West Pacific Paratrypaea .

Sakai (1999a) synonymised Trypaea and eight other genera with Callianassa , and later, Sakai (2005b) added a further two genera to this synonymy. Sakai (2011) revived the genus and synonymised five genera with Trypaea based on shared features of the male pleopods 1 and 2, which are poorly developed or absent in all callianassids. In doing so, he included 53 species.