Thomassinia

Poore, Gary C. B., 2015, Rediagnosis of Callianideidae and its genera (Crustacea: Decapoda: Axiidea), and description of a new species of Heardaxius Sakai, 2011, Zootaxa 3995 (1), pp. 229-240 : 237-238

Thomassinia de Saint Laurent, 1979

Thomassinia de Saint Laurent, 1979: 1396.— Kensley & Heard 1991: 528, 529.— Poore 1997: 410.— Sakai 2011:535 –536. Garyia Sakai, 2011: 530 –531 (type species, Thomassinia moorea Poore, 1997 , by original designation). New synonym

Type species. Thomassinia gebioides de Saint Laurent, 1979 (by original designation).

Diagnosis. Gonochoristic. Rostrum obsolete. Linea thalassinica complete (reaching posterior margin of carapace) or almost so. Thoracic sternite 7 with broad anterior part, well separating cushion-like coxae of pereopods 4. Pleomere 1 tergite with anterior part narrow, depressed. Eyestalks flattened, contiguous, with acute apex; pigmented cornea distal. Antennal scaphocerite minute and articulating. Maxilliped 3 merus without distal tooth, exopod absent, without crista dentata, ischium with toothbrush-like arrangement of stiff not-tapering even setae. Pereopods 1 similar, unequal, minor cheliped with longer fingers. Pereopod 3 propodus as long as broad, with distal spiniform seta. Pereopod 4 propodus without distal spiniform seta. Pereopod 5 subchelate, finger with distal row of spiniform setae. Setal-rows on anterolateral carapace, pleomere 1, pleomere 6 (3 rows). Pleopod 1 of male absent. Pleopod 2 of male without appendix masculina, with elongate appendix interna. Pleopods 2–5 rami without marginal filaments. Uropodal endopod with transverse row of short spiniform setae; exopod ovate, without dorsal plate.

Included species. T. aimsae Poore, 1997 ; T. gebioides de Saint Laurent, 1979; T. moorea Poore, 1997 .

Remarks. Species of Thomassinia differ from all other callianideids, and from all other axiideans, in the possession of a unique toothbrush-like arrangement of stiff blunt setae on maxilliped 3 ( Figs 1 g–j; Poore 1997: figs 34F, 37H). The shape of the eyestalks, the uropodal endopod with a transverse row of spiniform setae, and the absence of a dorsal plate on the uropodal exopod are common to all species.

The male pleopod 2 of all three species bears a simple elongate appendix interna ( Fig. 4 c, d). Poore’s (1997) figure 37K of T. gebioides shows a 2-articled appendix and is wrong. Sakai’s (2011) figure 72A of the pleopod 2 of T. moorea does not show the ‘subproximal appendix masculina with distal setae’ that he says it possesses.

Sakai (2011) erected the genus Garyia for T. moorea (type species) and Mictaxius arno Poore, 1997 , two very different species. He differentiated T. moorea from T. gebioides (type species of Thomassinia ) on the complete linea thalassinica (incomplete in T. gebioides ) and fused appendices masculina and interna (not fused). The visible extent of the linea thalassinica can not be considered of generic value in the face of the many characters that unite the two species. Sadly, it is concluded that Garyia is a junior synonym of Thomassinia .

Mictaxius arno lacks the characteristic maxilliped 3 and uropodal features seen in all three species of Thomassinia ; maxilliped 3 is setose with usual tapering setae but not with stiff non-tapering blunt setae, the uropodal exopod has an overlapping arrangement of marginal spiniform setae), the cornea are dorsal, the appendix interna on the male pleopod 2 is cylindrical, with apical hooks, and with the appendix masculina fused mesially, and pereopod 5 is not subchelate. Mictaxius thalassicola is similar except that the uropodal endopod has a dorsal plate more typical of that seen in some Callianassidae .

c d e

a b

Figures

FIGURE 1. Heardaxius rogerbamberi n. sp. Holotype. a, b, habitus in lateral and dorsal views. c, coxa of pereopods 2 – 4 and thoracic sternite 7 in ventral view (male and female gonopores arrowed). d, left cheliped. e, pleomere 6, telson and uropods. Dissected left maxilliped 3, mesial views. f, Heardaxius rogerbamberi, holotype. g, Thomassinia aimsae (MNHN IU- 2013 - 7082). h, i, Thomassinia gebioides, with detail of meral setae (FMNH UF 38171). j, Thomassinia moorea (FMNH UF 29264). Black scale bars = 1 mm; white scale bar (f, g, i,, j) = 0.1 mm).