Pseudopinnixa Ortmann, 1894

Komai, Tomoyuki & Konishi, Kooichi, 2012, Reappraisal of the Systematic Position of the Supposed Pinnotherid Crab Pseudopinnixa carinata (Crustacea: Decapoda: Brachyura), Species Diversity 17 (1), pp. 29-37 : 29-30

Genus Pseudopinnixa Ortmann, 1894

Pseudopinnixa Ortmann, 1894: 694 ; Schmitt et al. 1973: 126; Sakai 1976: 586.

Type-species. P seudopinnixa carinata Ortmann, 1894 , by monotypy (see Remarks).

Diagnosis.C arapace subtrapezoidal in general shape with rounded margins, wider than long; dorsal surface smooth, regions not demarcated, trace of cervical groove discernible; frontal margin slightly produced medially; no teeth on anterolateral margin; posterolateral margin weakly delimited. Orbit small; eye completely lling orbit, movable; lower orbital margin clearly separated from suborbital ridge, unarmed. Epistome broad, medially concave, posterior margin pointed medially. First to third thoracic sternites of male clearly separated by transverse sutures; anterior margin of rst sternite broad, trilobed; anterolateral angles of second sternite produced anteriorly. ffiird maxillipeds completely

lling buccal cavern, no gape when closed; articulation between ischium and merus distinct, transverse; dactylus distinctly longer than propodus, spatulate, bearing prominent tu of setae on magins and inner face, setae reaching concavity of rst to third thoracic sternites; exopod with mesial half covered by lateral margin of ischium-merus of endopod, agellum short. Chelipeds equal or subequal, ngers subequal in length to palm; no tu or patch of setae at base of gape between ngers. Anterior part of male thoracic sternum with shallow median concavity to accommodate elongate setae on dactylus of third maxilliped. Male abdomen moderately narrowly triangular, third to sixth somites functionally fused but with suture lines distinct on outer surface. First gonopod compressed laterally, cross-section subovate. Second gonopod much shorter than rst gonopod.

Distribution.K nown only from Japan.

Remarks.Or tmann (1894) did not designate a type species for his new genus Pseudopinnixa , but Pseudopinnixa carinata should be regarded as the type species by monotypy (see Ng et al. 2008). Holmes (1894: 565) proposed a new genus, Pseudopinnixa , for a pinnotherid species Pinnixa nitida Lockington, 1876 known from the eastern Paci c, but Holmes himself realized that the name Pseudopinnixa had been already used by Ortmann (1894) ( Holmes 1894: 587). In this same paper, Holmes (1984: 587) proposed a replacement name Parapinnixa Holmes, 1894 for his Pseudopinnixa .

As mentioned before, the systematic position of Pseudopinnixa carinata has recently been the subject of discussion. Cuesta et al. (2005) rst suggested a close relationship of this taxon to members of Grapsoidea and Ocypodoidea, especially the Macrophthalmidae . Palacios-ffieil et al. (2009) commented that Pseudopinnixa might warrant eventual treatment as a separate family of the Pinnotheroidea. Our examination, however, has revealed that P. carinata has the diagnostic characters of the Gaeticinae (see Davie and Ng 2007): (1) the distal three segments of the third maxilliped are elongate, with the dactylus possessing long, brush-like setae probably associated with suspension feeding; (2) the anterior part of the thoracic sternum has a shallow median concavity, in which setae on the dactylus of the third maxil- liped are accommodated; and (3) the third to sixth abdominal somites of the male are functionally fused although the sutures are clearly de ned on the outer surface. In addition, the following characters are shared with Sestrostoma : (1) the carapace is devoid of anterolateral teeth; (2) the orbit is small, lled by the eye; and (3) the anterolateral angles of the second thoracic sternite are produced anteriorly. As a result of these observations, we propose to transfer P. carinata , to the Gaeticinae .

Pseudopinnixa is unique within the Gaeticinae in having the following features: (1) the carapace is roundly subtrapezoidal; (2) there is no inner orbital tooth on the lower orbital margin; (3) the male rst thoracic sternite is trilobed anteriorly; (4) the mesial half of the exopod of the third maxilliped is covered by the lateral margin of the ischiummerus of the endopod; and (5) the rst gonopod is laterally compressed, its cross-section being subovate. ffie carapace is more distinctly trapezoidal with posteriorly converging lateral margins in Gaetice , and nearly elliptical in Gopkittisak and Sestrostoma . ffie lower orbital margin has a distinct inner orbital tooth and the male rst thoracic sternite is triangular in Gaetice , Gopkittisak , and Sestrostoma . ffie exopod of the third maxilliped is fully exposed ( Gaetice ) or slightly hidden mesially ( Gopkittisak and Sestrostoma ). ffie

rst gonopod is triangular in cross-section in all three genera.

As Cuesta et al. (2005) noted, substantial similarity is seen between the rst stage zoea of P. carinata , which was described by Muraoka (1985), and those of the other known varunid taxa. Shared characters include the possession of dorsolateral knobs on the second and third abdominal somites, the distally forked telson without armature, 2+2 maxillar setation, and 0,1,5(6) setation of the endopod of the second maxilliped (cf. Hart 1935; Kurata 1968a, b; Wear 1970; Morita 1974; Scelzo and Lichtschein de Bastida 1979; Wilson 1980; Terada 1981; Kim and Lee 1983; Kim and Jang 1987; Lee 1988; Kim and Hwang 1990; Rodrígez et al. 1992; Hwang et al. 1993; Guerao et al. 1995; Hwang and Kim 1995; Cuesta and Schubart 1997; Cuesta et al. 2000, 2001; Spivak and Cuesta 2000). However, the antenna of the rst zoea of P. carinata has a reduced exopod, and in this regard is unique among known varunids but similar to rst zoeae of species of Plagusia in the Plagusiidae Dana, 1851 (see Schubart et al. 2010). ffiis could be the result of convergence rather than an indication of a close relationship. In addition, the presence of three setae on the basal segment of the rst maxilliped and the three-segmented endopod of the second maxilliped, which are typical of rst zoeae of Grapsoidea but not Pinnotheroidea, further support the removal of Pseudopinnixa from the Pinnotheridae .