Rhynchoplax messor Stimpson 1858
Creators: name: Poore, Gary C. B.
name: Guinot, Danièle
name: Komai, Tomoyuki
name: Naruse, Tohru
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Hymenosomatidae
Rhynchoplax
Rhynchoplax messor

description: Rhynchoplax messor Stimpson, 1858
(Fig. 3)
Rhynchoplax messor — Stimpson, 1858: 109.— Stimpson 1907: 148. — Tesch 1918: 18. — Sakai 1934: 289, fig. 5a. — Sakai 1935: 70, fig. 27. — Sakai 1938: 197 –198, fig. 1, pl. 20 fig. 2. — Sakai 1965: 63, fig. 9, pl. 25 fig. 2. –– Sakai 1976: 147 –148, textfig. 76c (English text), pl. 46 fig. 2, 92 (Japanese text). –– Miyake 1983: 192, pl. 64 fig. 6.
Halicarcinus messor— Lucas 1980: 163, fig. 9A. — Dai & Yang 1991: 116 –117, fig. 59. — Kim 1992: 257. –– Ng et al. 1999: 88– 89, fig. 4.
Not Rhynchoplax messor — Yokoya 1928: 761 –762, fig. 1 [= Stimpsoplax setirostris (Stimpson, 1858)].
Material examined. Japan. Chiba Prefecture, Ubara, Katsuura, intertidal, 3 June 1996, coll. E. Nishi, CBM-ZC 3507 (1 male, 4.8 mm). Hasama, Tateyama, intertidal, 22 July 2001, coll. T. Komai, CBM-ZC 6024 (1 ovigerous female, 4.3 mm). [Shizuoka Prefecture], S[h]imoda, AM P.10497 (3 males, largest 3.3 mm; 3 females, largest 3.0 mm, 1 ovigerous female, 3.0 mm). Wakayama Prefecture. Kushimoto, Shionomisaki, Naminoura, 9 m, 16 May 1978, SCUBA diving, coll. S. Yamaguchi, CBM-ZC 4163 (1 ovigerous female, 4.0 mm).
Diagnosis. Carapace 1.1 times as wide as long; subhepatic region inflated, forming low elevation visible in dorsal view, with 2 conspicuous tubercles inferior to subhepatic elevation (not visible in dorsal view); anterolateral margin with minute tubercles (sometimes greatly reduced); epibranchial spine present, sharp; dorsum with gastrocardiac groove, cardiac median ridge. Male rostrum about 0.3 as long as carapace, spatulate with slightly convex lateral margins, with pair of small but sharp supraocular spines proximally; apex without long setae. Female rostrum narrower, tapered, length similar to that of male. Supraocular eave poorly developed; postocular margin with small acute spine. Supraocular spines small, at base of rostrum just mesial to base of eyestalk. Eyestalks compact, with small protuberance on anterior surface ventrally. Maxilliped 3 merus rounded distolaterally. Cheliped in male at most twice carapace length, with fairly swollen propodus, fixed finger with denticulate cutting edge; dactylus with simple proximal tooth, excavate in middle third; gape obscured by dense mat of setae; carpus short, cup-like; merus widened distally, with blunt dorsodistal tubercle. Pereopods 2–5 meri each with prominent dorsodistal tubercle; pereopod 2 dactylus weakly arcuate, not falcate, dactyli of pereopods 3–5 falcate. Male gonopore with prominent penial process. Gonopod 1 with swollen base, almost straight section, strongly curved tip terminating in fine apex. Gonopod 2 small, strongly flattened, terminating in short, non-tapered, terminally truncate tube-like process; lateral margin expanded into angular lobe, mesial margin gently concave.
Distribution. East Asian endemic: Japan, Korea and China, intertidal to 9 m.
Remarks. This species has been mentioned in literature often and the dorsal habitus illustrated several times. Sakai (1934, 1935, 1976) and Lucas (1980) figured the gonopod 1. Sakai (1938) figured the dactylus of pereopod 4 and the male pleomeres 3 and 4 erroneously as free. Sakai (1965: fig. 9) figured the maxilliped 3 and the male pleon, and again stated that ‘the male abdomen is composed of six distinct segments.’ Ng et al. (1999) illustrated variation of the male rostrum. Re-examination of material from the type locality and elsewhere confirmed characters in earlier figures.
description: Published as part of Poore, Gary C. B., Guinot, Danièle, Komai, Tomoyuki & Naruse, Tohru, 2016, Reappraisal of species attributed to Halicarcinus White, 1846 (Crustacea: Decapoda: Brachyura: Hymenosomatidae) with diagnosis of four new genera and one new species from New Ireland, Papua New Guinea, pp. 480-514 in Zootaxa 4093 (4) on pages 491-493, DOI: 10.11646/zootaxa.4093.4.2, http://zenodo.org/record/258478