Indopinnixa Manning & Morton, 1987

Komai, Tomoyuki, Naruse, Tohru, Yokooka, Hiroyuki, Taru, Masanori, Shimetsugu, Miho & Watanabe, Tetsuya, 2022, Redescription of Pinnixa haematosticta Sakai, 1934, its transfer to Indopinnixa Manning & Morton, 1987, and a reappraisal of Indopinnixa kumejima Naruse & Maenosono, 2012 (Decapoda: Brachyura: Pinnotheridae), Zootaxa 5100 (3), pp. 361-389 : 364-365

Genus Indopinnixa Manning & Morton, 1987

Indopinnixa Manning & Morton, 1987: 543 .— Rahayu & Ng 2010: 59 .

Type species. Indopinnixa sipunculana Manning & Morton, 1987 .

Emended diagnosis. Carapace much wider than long, transversely elliptical; integument firm; front narrow, with shallow median groove; dorsal surface generally glabrous, sparsely punctate, regions poorly defined, sometimes with blunt or clearly demarcated transverse ridge across cardiac region, ridge not extending entirely across carapace; orbit broadly ovate, with wide inner hiatus partly occupied by basal article of antennal peduncle. Eyestalks very short, completely filling orbits. Antennular peduncles folded into wide fossae, separated by shallow median septum, under front. Maxilliped 3 with ischium and merus completely fused (= ischiomerus), narrow, subtrapezoidal; palp (carpus + propodus + dactylus) as long as or longer than ischiomerus; propodus and dactylus flattened, tongue-shaped; dactylus articulated to middle portion of flexor margin of propodus, far overreaching rounded distal margin of propodus. Chelipeds compressed, setose; palm with a longitudinal line of granules and setae along midline of outer surface; fingers slender, dactylus upper margin typically with row of long setae. Ambulatory pereopods (pereopods 2–5) relative lengths P4> P3 ≥ P2> P5; pereopod 4 heavy, merus particularly stout, marginally granulate or dentate. Male pleon constricted, with at least somites 5 and 6 functionally fused (sutures between somites may be discernible); no gonopodal plate developed on inner side; telson much wider than long, wider than pleomere 6. Female pleon consisting of six free somites, not concealing lateral parts of thoracic sternum. Male gonopod 1 tapering distally, but shape and setation of distal part variable according to species.

Composition. Seven species (all from the Indo-West Pacific): Indopinnixa haematosticta ( Sakai, 1934) n. comb., I. kasijani Rahayu & Ng, 2010 , I. moosai Rahayu & Ng, 2010 , I. mortoni Davie, 1992 , I. oryza Naruse & Maenosono, 2012 , I. shellorum Ng, 2014 and I. sipunculana (type species).

Remarks. The monophyly of Pinnixa has been questioned (e.g., Rahayu & Ng 2010; Naruse & Maenosono 2012; Palacios Theil et al. 2016), and recently, Palacios Theil & Felder (2020) partially revised American species assigned to Pinnixa and allied genera based on molecular phylogenetic analysis in combination with morphological studies. As a result, Pinnixa was restricted to its type species P. cylindrica (Say, 1818) , and the other 20 species reexamined were reassigned to Glassella Campos & Wicksten, 1997 , Scleroplax Rathbun, 1894 and the three newly established genera, Rathbunixa Palacios Theil & Felder, 2020 , Sayixa Palacios Theil & Felder, 2020 and Tubicolixa Palacios Theil & Felder, 2020 . The generic placement of the seven Asian species ( Pinnixa balanoglossana Sakai, 1934 , P. banzu Komai, Nishi & Taru, 2014 , P. haematosticta Sakai, 1934 , P. lata Komatsu & Takeda, 2009 , P. penultipedalis Stimpson, 1858 , P. rathbuni Sakai, 1934 , and P. tumida Stimpson, 1858 ), however, were not addressed.

Manning & Morton (1987) distinguished Indopinnixa from Pinnixa s.l. primarily by the fusion of the male pleomeres 5 and 6, rather than all pleomeres been freely articulated in Pinnixa s.l. However, Naruse & Maenosono (2012) argued that species assigned to Pinnixa at the time exhibit various degree of fusion of the male pleomeres. The molecular phylogenetic analyses by Palacios Theil & Felder (2020) placed a clade including Indopinnixa kumejima and I. moosai in sister relation to a clade including some species of Pinnixa s.l. [ P. abbotti Glassell, 1935 , P. arenicola Rathbun, 1922 , P. floridana Rathbun, 1918 Glassella costaricana ( Wicksten, 1982) , Laminapinnixa miamiensis McDermott, 2014 , and Laminapinnixa faxoni ( Rathbun, 1918) ]. On the basis of the inferred phylogenetic pattern, Laminapinnixa McDermott, 2014 was synonymised with Glassella Campos & Wicksten, 1997 in spite of the considerable difference in the structure of the maxilliped 3; while Indopinnixa and Glassella were maintained as distinct genera for the time being. From the morphological perspective, species assigned to Indopinnixa and Glassella share the following features: at least pleomeres 4–6 are functionally fused, although sutures are sometimes evident on the outer surface; the telson does not taper, being wider than the narrowest portion of the pleomere 6; the maxilliped 3 dactylus is large and heavy, longer than the propodus; the external surface of the chela palm often bears longitudinal ridges or lines of granules on the midline; the pereopod 4 is very stout (cf. Manning & Morton 1987; Davie, 1992; Rahayu & Ng 2010; Naruse & Maenosono 2012; Ng 2014; Palacios Theil & Felder 2020; Felder & Palacios Theil 2020). Species assigned to Indopinnixa differ from those assigned to Glassella as diagnosed by Palacios Theil & Felder (2020) in the absence of a gonopodal plate developed on the inner side of the male pleon and the rather simple, generally tapering gonopod 1 (although the shape of the distal part is rather variable according to species). In species assigned to Glassella , all from the West Atlantic, including the Gulf of Mexico and the Caribbean Sea, the male pleon has a gonopodal plate or sheath extending between or against gonopods (cf. McDermott 2014; Palacios Theil & Felder 2020); and the male gonopod 1 is relatively stout, terminally forming sharp angle, spinose tip, or distally to laterally directed corneous filament. Differentiating characters among the genera of Pinnixinae Števčić, 2005 refer to Palacios Theil & Felder (2020).

Our studies show that Pinnixa haematosticta agrees closely with Indopinnixa , and is in fact, very similar morphologically to I. kumejima . Here the generic diagnosis of Indopinnixa is emended, and Pinnixa haematosticta is transferred to Indopinnixa .