Frevillea rosaea A. Milne-Edwards, 1880

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 56-59

Frevillea rosaea A. Milne-Edwards, 1880

Frevillea rosaea A. Milne-Edwards 1880b: 15 [ St. Vincent]. — A. Milne-Edwards & Bouvier 1923: 337, pl. 6, fig. 1 [diagnosis; St. Vincent]. — Chace 1940: 47 [ Cuba]. — Guinot 1969b: 513; 1971: 1080 [in list]. — Soto 1985: 483; 1986: 3, 4, 33; 1991: 627 [Florida]. — McLaughlin et al. 2005: 257 [in list]. — Ng et al. 2008: 78 [in list].

Goneplax rosaea — Rathbun 1918: 25 [in key], 27.

Type material. Female lectotype, 15.7 mm × 22.7 mm, 1 male paralectotype, 10.1 mm × 16.3 mm, 1 preadult female paralectotype, 5.0 mm × 7.9 mm ( MNHN-B10152 ) .

Type locality. West Indies , off St. Vincent, 13°06.75’N, 61°06.9’W, 158 m.

Material examined. West Indies. U.S. C.S.S. Blake, stn. 232: female lectotype, 15.7 mm × 22.7 mm, 1 male paralectotype, 10.1 mm × 16.3 mm, 1 pre-adult female paralectotype, 5.0 mm × 7.9 mm (MNHN- B10152 ) .

Diagnosis. See Remarks for Frevillea .

Remarks. The known type material of F. rosaea consists of three specimens, one male, one female, and one pre-adult female (MNHN-B10152). Labels indicate “type” and “juv. cotypes” without any indication as to which specimen is the actual holotype. No additional information is given in the description (A. Milne- Edwards 1880b: 15), and as such, all the specimens must be regarded as syntypes. A subsequent publication with a more detailed account of the species (A. Milne-Edwards & Bouvier 1923: 337) refers to a female as the “type” (le type chargé d’oeufs) and the specimen illustrated is similarly referred to as type femelle (A. Milne- Edwards & Bouvier 1923: 337). Rathbun (1918: 27) referred to the “female holotype in Paris Mus. (After A. Milne Edwards.)”. The action by A. Milne-Edwards & Bouvier (1923) is equivalent to the selection of a lectotype for the species. A. Milne-Edwards & Bouvier also referred to the three other specimens.. These specimens are all paralectotypes. The whereabouts of the presumed fourth specimen is unknown. It is not found in the collections of the Museum of Comparative Zoology (MCZ), Harvard University, where part of the type material of F. barbata is deposited (see above) as both species were described from the same Blake material collected by L. Agassiz.

The female specimen (15.7 mm × 22.7 mm) is here regarded as the lectotype and a damaged male without gonopods (10.1 mm × 16.3 mm) and the pre-adult female (5.0 mm × 7.9 mm) as paralectotypes. All three specimens are part of the same lot catalogued as MNHN-B10152.

Distribution. Western Atlantic from Florida and the West Indies. Depth: 159–476 m ( Soto 1986).

Genus Henicoplax n. gen.

Heteroplax — Miers 1879: 39 [discussion] (part). — Balss 1922a: 136 (part). — Sakai 1939: 555 [in key], 560 (part); 1976: 531 (part). — Guinot 1969b: 511 (part); 1971: 1080 [in list] (part). — Serène & Lohavanijaya 1973: 71 [discussion] (part). — Karasawa & Kato 2003b: 130 [in list] (part). — Ng et al. 2008: 78 [discussion] (part). — De Grave et al. 2009: 33 [in list] (part).

Otmaroplax Števčić 2005: 134 [nomen nudum] (part).

Diagnosis. Carapace ( Figs. 21A; 22A; 23A; 25A; 26A, C) hexagonal, transversely rectangular, wider than long, convex; anterolateral borders short, nearly straight; dorsal surface smooth without clear indication of regions, transverse depression (postorbital ridge; Fig. 25A) below each orbit extending from anterolateral tooth, becoming progressively shallower before disappearing at level of eye (absent in H. trachydactylus n. sp.); front wide, straight, median notch absent or barely visible, truncate margin. One triangular, short anterolateral tooth posterior to much larger, triangular, anteriorly-oriented outer orbital tooth. Orbits long, longer or almost as long as front (e.g. Figs. 22A, C; 23A, C), sinuous, thin, entire (notches absent) supraorbital border; thin, weakly granular, entire (notches absent), sinuous suborbital border with broad median lobe; inner suborbital tooth absent (e.g. Figs. 21E; 22C; 23C; 26E). Eye peduncles long, more than half of frontal width, much longer than large, slightly elongated corneas (e.g. Figs. 21A, 22C, 23C). Basal antennal article slightly mobile without disto-lateral process, orbital hiatus is closed excluding antennal flagellum from orbit ( Figs. 22C, 23C). Anteroexternal margin of third maxilliped merus auriculiform or angular. Cheliped fingers moderately stout, very short granules on dorsal margin of dactylus, slightly longer than slender propodus, light coloured; setation varying from short, simple, setae on anterior margin of carpus, propodus to dense tomentum on dactylus, propodus, carpus, merus ( H. eriochir n. sp.; Fig. 21B). Dorsal margins of ambulatory legs (P2–P5) meri, carpi, propodi unarmed, dactyli slender, smooth, setose; P5 propodus long, subcylindrical, fringed with setae; dactylus, long, slender, fringed with setae ( Fig. 27A, B). Thoracic sternum ( Figs. 21D, F; 22E; 23D; 25G; 26F) wide; thoracic suture 2/3 complete, convex ( Figs. 21B; 23B; 26F); 3/4 deep, short, interrupted; 4/5, 6/7, 7/8 interrupted, 5/6 complete ( Figs. 21D, F; 23D; 25G; 26F); median groove on thoracic sternites 7, 8. Sternoabdominal cavity of male deep, only reaching median portion of sternite 4, anterior extremity rounded ( Figs. 21D; 22B; 25B; 26B). Press-button of male abdominal-locking mechanism as small tubercle near thoracic suture 4/5 ( Fig. 21D). Male abdomen narrow, slender, transversely narrow telson, lateral margins of somites 4–6 abruptly narrowing from somite 3 to narrow telson ( Figs. 21C; 22D; 25B); somite 3 reaching inner margins of P5 coxae ( Figs. 21C; 22D; 25C, D), sometimes locking under thoracic sternite 7 ( Fig. 25D), no portion or small portion ( Figs. 22D; 25D) on each side of thoracic sternite 8 left exposed by closed abdomen, somite 2 transversely almost as long as somite 3 (except H. eriochir n. sp., where somite 2 transversely shorter than somite 3 leaving large portion on each side of thoracic sternite 8 left exposed by closed abdomen; Fig. 21C). G1 long, slender, slightly sinuous ( Fig. 22E), acuminate apex (transversely cut in H. nitida and H. pilimeles n. sp. [ Fig. 24G–J], slightly transverse in H. maldivensis [ Fig. 24D, E]), with relatively few, small denticles ( Figs. 24A, B, D, E, G–J; 27C, D); G2 less than one-third of G1, straight, apex with 2 unequal processes: one long, tip obtuse or acute; second much shorter, tip obtuse or acute ( Figs. 24C, F, K; 27E). Male genital opening (gonopore) coxal; coxo-sternal disposition of long penis, protected by concave posterior portion of thoracic sternite 7 ( Figs. 21D; 22E; 25E). Vulva small, ovoid, slightly elongated, extending transversely across anterior portion of sternite 6 close to median axis of thorax, sternal vulvar cover absent ( Figs. 21F; 23D; 25G; 26F).

Type species. Heteroplax nitida Miers, 1879 (by present designation, gender feminine).

Etymology. From henikos, Greek for “single”, in reference to the single anterolateral tooth diagnostic of the genus, and plax, Greek for “plate” or “tablet”, which is derived from the generic name Heteroplax to denote that the type species of the new genus was formerly included in Heteroplax sensu lato.

Remarks. The revision of the genus Heteroplax Stimpson, 1858 , with H. transversa as its type species, necessitates the assignment of several species that were long confused with H. transversa to other genera that do not share the same type of carapace and other characters of Heteroplax . One of these genera is Henicoplax n. gen., established here to receive Goneplax maldivensis Rathbun, 1902 , and H. nitida Miers, 1879 , plus three new species, all Indo-West Pacific in distribution. Diagnostic of the new genus is the presence on each side of the carapace of only one small and triangular anterolateral tooth (but not large and acute as in Frevillea or Nancyplax ), which are similar in shape to the outer orbital teeth. Also unique is the conspicuous transverse depression, or postorbital ridge, found in four of its five species ( H. eriochir n. sp., H. maldivensis , H. nitida , and H. pilimeles n. sp.; see Table 3) and that extends just below the orbits from each anterolateral tooth. In contrast to the ridge of Platyozius Borradaile, 1902 ( Fig. 34E), it does not extend along the entire width of the carapace ( Fig. 25A). Table 1 contrasts the new genus with other euryplacid genera.

All five species of Henicoplax n. gen. are small in size and apparently restricted to soft sediments in relatively shallow water. A small ovigerous female from the Andaman Sea coast of Thailand that was examined (3.3 mm × 4.9 mm; Thai-Danish Expedition, stn. 1020–9, 09°28’N, 97°57’E, 42 m, 12.01.1966, ZMUC CRU- 10072) and identified as Heteroplax nitidas [sic] by Serène & Soh (1976: 23) may represent an undescribed sixth species of Henicoplax n. gen. A postorbital ridge was present but the anterolateral tooth was acute and the orbits and eye peduncles were proportionally shorter than in H. nitida or its congeners. Although we have not examined the specimen, the importance of the morphology of the G1 for identifying members of this genus means that it is best to wait until males become available.

Species included.

Henicoplax eriochir n. sp.

Henicoplax maldivensis ( Rathbun, 1902)

Henicoplax nitida ( Miers, 1879)

Henicoplax pilimeles n. sp.

Henicoplax trachydactylus n. sp.

The genus is restricted to the Indo-West Pacific region.