Euryplax polita Smith, 1870

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 50-53

publication ID	https://doi.org/ 10.11646/zootaxa.2375.1.1
persistent identifier	https://treatment.plazi.org/id/03F487A8-396D-4210-7D8C-FA99F630FC9F
treatment provided by	Felipe
scientific name	Euryplax polita Smith, 1870
status

Treatment

Euryplax polita Smith, 1870 View in CoL

( Fig. 18C, D View FIGURE 18 )

Euryplax politus Smith, 1870: 163 View in CoL [Pacific coast of Panamá].

Euryplax polita View in CoL — Rathbun 1918: 34 [in key], 36. — Glassel 1934: 301 [in list; Gulf of California]. — Guinot 1969b: 512 [discussion], pl. 2, fig. 1 [holotype]; 1971: 1080 [in list]; 1984: pl. 1, fig. E [holotype]. — del Solar 1970: 44 [ Perú]. — del Solar et al. 1970: 27 [ Perú]. — Garth 1960: 118 [in list]; 1961: 135, 136 [in list], 154 [Pacific coast of Mexico]; 1992: 3, 6 [in list] [Pacific coast of Mexico]. — Hendrickx 1992: 8 [in list]; 1993a: 314 [in list]; 1993b: 10 [in list]; 1994: 110 [in list]; 1995: 139 [in list]; 1996: 616, 617 [in list] [Pacific coast of Mexico]. — Ng et al. 2008: 78 [in list].

Type material. Male holotype ( YPM 660 About YPM ; Guinot 1969b: fig. 1) .

Type locality. Pacific coast of Panamá, unknown location .

Material examined. Mexico (?) SIPCO IIB 1, V.V.P., 29.08.1981: 1 male, 9.8 mm × 16.4 mm, 1 female, 9.7 mm × 15.4 mm ( MNHN-B24040 ) .

Mexico. Isabel I., Sinaloa, Velero, stn. 747–37, 18– 33 m, 2.04.1937: 1 male, 4.7 mm × 7.0 mm ( LACM) ; stn. 870–38, 18– 27 m, 8.03.1938: 2 males, 1 pre-adult female ( LACM) ; stn. 974–39, 27– 46 m, 9.05.1939: 1 male, cl 8.6 mm [remainder of carapace damaged] ( LACM) .

Revillagigedo Is., Socorro I., Braithwaite Bay, Velero, stn. 131–34, 3.01.1934: 1 pre-adult female ( LACM).

Petlatán Bay, Velero, stn. 264–34, 14 m, 3.03.1934: 2 pre-adult females, 5.4 mm × 7.9 mm, 5.5 mm × 8.2 mm ( LACM).

Chacahua Bay , Velero, stn. 765–38, 9– 18 m, 9.01.1938: 1 male ( LACM); stn. 767–38, 73– 91 m, 9.01.1938: 1 male, 4.9 mm × 7.4 mm ( LACM) .

Tangola-Tangola Bay , Velero, stn. 259–34, 8– 11 m, 28.02.1934: 1 male, 5.7 mm × 9.1 mm ( LACM) .

Tangola-Tangola Bay , Eastern Pacific Zaca Expedition, stn. 196, D–6, D–8, no. 37,592, 16– 13 m, 9.12.1937: 1 male, 5.4 mm × 8.2 mm, 1 female, 5.7 mm × 8.9 mm ( LACM) ; stn. 196, D–13, no. 37,620, 18 m, 12.12.1937: 1 male, 8.7 mm × 14.7 mm ( LACM) ; stn. 196, D–17, 42 m, 13.12.1937: 1 pre-adult female, 4.3 mm × 6.0 mm ( LACM) .

Guatemala. Off San José Light , Velero, stn. 931–39, 42 m, 23.03.1939: 3 pre-adult females ( LACM) .

Panamá. Taboga I., Velero, stn. 960–39, 1– 3 m, 2.05.1939: 1 male, 7.1 mm × 11.2 mm ( LACM) .

Piña Bay, Velero, stn. 438–35, 46 m, 29.01.1935: 1 pre-adult female ( LACM).

Ecuador. La Libertad, Velero, stn. 209–34, 4– 6 m, 9.02.1934: 1 female, 5.8 mm × 8.8 mm, 1 ovigerous female, 5.6 mm × 8.3 mm ( LACM) .

Perú. Caleta La Cruz , Tumbes, no. B–117, E. M. del Solar coll., 15 m, sand, 18.03.1970: 1 male, 18.9 mm × 33.8 mm ( LACM) .

Sechura Bay , Velero, stn.845–38, 17 m, 15.02.1938: 1 female, 6.6 mm × 10.5 mm ( LACM) .

Diagnosis. Outer orbital angle typically (but not always) expanded anteriorly, broad ( Fig. 18C View FIGURE 18 ). Dorsal surface of cheliped merus without depression near anterior margin.

Remarks. Differences between E. polita and its close congener, E. nitida , are given in the Remarks section of the latter.

Distribution. Tropical Eastern Pacific region, from the Gulf of California to Perú. Depth: shallow subtidal to 91 m.

Genus Frevillea A. Milne-Edwards, 1880

Frevillea A. Milne-Edwards, 1880b: 15 View in CoL . — A. Milne-Edwards & Bouvier 1923: 335 [diagnosis]. — Guinot 1969b: 513

[discussion], 520; 1971: 1080 [list of species]. — Abele & Kim 1986: 591 [in key]. — Ng & Castro 2007: 44 [in list]. — Ng et al. 2008: 78 [in list]. — De Grave et al. 2009: 33 [in list]. Freyvillea [sic] — Alcock 1900: 292 [in list]. Goneplax View in CoL — Rathbun 1918: 16 [in key], 25 (part); Manning & Holthuis 1981: 164 (part). Fravillea [sic] — Karasawa & Kato 2003a: 151 [in list]; 2003b: 139 [in list].

Diagnosis. Carapace ( Figs. 18E, F View FIGURE 18 ; 19A View FIGURE 19 ) quadrate, slightly wider than long, dorsal surface smooth without clear indication of regions; anterolateral borders straight, nearly parallel to each other; front wide, slightly bilobed with small median prominence or straight. One acute anterolateral tooth posterior to slender, acute, outwardly oriented outer orbital tooth; long, sinuous median lobe on thin suborbital border, triangular inner suborbital tooth ( Fig. 19B, C View FIGURE 19 ). Orbits long, longer than front; eye peduncles long, nearly as long as front, longer than corneas; corneas reniform, dorsoventrally flattened ( Figs. 18E, F View FIGURE 18 ; 19A, B View FIGURE 19 ). Basal antennal article does not fill orbital hiatus ( Fig. 19B View FIGURE 19 ; Guinot 1969b: fig. 40), made immobile by small process at inner edge of suborbital border. Anteroexternal margin of third maxilliped merus auriculiform ( Fig. 19C View FIGURE 19 ). Cheliped fingers ( Fig. 19E View FIGURE 19 ) moderately slender, shorter than propodus, light in colour; carpus with tooth on inner margin; dense tomentum on posterior margin of propodus and anterior margin of carpus ( Figs. 18E, F View FIGURE 18 ; 19A View FIGURE 19 ). Dorsal margins of ambulatory legs (P2–P5) meri, carpi, propodi unarmed, dactyli slender, smooth, setose. P5 ( Figs. 18E, F View FIGURE 18 ; 19A View FIGURE 19 ) propodus subcylindrical, fringed with long setae; dactylus long, slender. Thoracic sternum ( Fig. 19F, H View FIGURE 19 ) wide; thoracic suture 2/3 complete, slightly convex ( Fig. 19H View FIGURE 19 ); 3/4 deep, short, interrupted; 4/5, 6/7, 7/8 interrupted, 5/6 complete ( Fig. 19F, H View FIGURE 19 ); median groove on thoracic sternites 7, 8 ( Fig. 19F View FIGURE 19 ). Sterno-abdominal cavity of male deep, reaching anterior margin of sternite 4 ( Fig. 19F View FIGURE 19 ). Press-button of male abdominal-locking mechanism as large tubercle near thoracic suture 4/5 (presence in pre-adult females unknown). Male abdomen ( Fig. 19D View FIGURE 19 ) moderately wide, triangular (not T-shaped), proportionally narrow telson; somite 3 transversely longer than somites 4–6, reaching inner margins of P5 coxae, fitting under episternite 7; no portion of thoracic 8 exposed by closed abdomen, somite 2 transversely as long as somite 3 ( Fig. 19G View FIGURE 19 ; Guinot 1969b: fig. 33). G1 long, slender, slightly sinuous, acuminate apex, with relatively large denticles ( Figs. 19F View FIGURE 19 ; 20D, E View FIGURE 20 ); G2 less than one-third of G1, straight, apex with 2 unequal processes ( Fig. 20F View FIGURE 20 ). Male genital opening (gonopore) coxal; coxo-sternal disposition of long penis with broad proximal portion, protected by concave posterior portion of thoracic sternite 7 ( Fig. 19F View FIGURE 19 ). Vulva rounded, extending across most of median portion of sternite 6 close to median axis of thorax ( Fig. 19H View FIGURE 19 ); thick, slightly elevated posterior margin, covered by soft membrane, sternal vulvar cover absent.

Type species. Frevillea barbata A. Milne-Edwards, 1880 View in CoL (by designation, Rathbun 1918: 25; gender feminine).

Remarks. Frevillea was sometimes confused with Goneplax Leach, 1814 (i.e. Rathbun 1918: 25), a genus that is clearly included in the Goneplacidae , even if both taxa share the general morphology of the dorsal surface of the carapace (see Guinot 1969b: 515; Castro 2007: 619).

The inclusion of Frevillea in the Euryplacidae is clear, even if the genus has some unusual features. Unique among euryplacid genera is a basal antennal article that does not fill the orbital hiatus ( Guinot 1969b: 515, fig. 40). The male abdomen of Frevillea , a Western Atlantic genus, is intermediate between the slender, T-shaped abdomen of Indo-West Pacific genera and the wide, triangular abdomen of three Western Atlantic and Tropical Eastern Pacific genera ( Fig. 1 View FIGURE 1 ). Such a moderately wide but clearly not triangular male abdomen ( Fig. 19D View FIGURE 19 ) is shared with Euryplax and Machaerus ( Fig. 1B View FIGURE 1 ). Unusual among euryplacids are the reniform eyes with the corneas dorsoventrally flattened ( Figs. 18E, F View FIGURE 18 ; 19A, B View FIGURE 19 ), a trait shared with the euryplacid Psopheticoides ( Fig. 36B View FIGURE 36 ).

The separation between the three described species of Frevillea , all of which are sympatric in at least part of their geographical distribution in the Western Atlantic, is ambiguous and as a result not always clear. Rathbun (1918: 25), in a key to the American species of Goneplax that included the three species of Frevillea , separated F. barbata from F. hirsuta and F. rosaea by having the sides of the carapace “strongly convergent posteriorly” in contrast to being “almost parallel” in the other two species. Such differences are not apparent in the material examined ( Figs. 18E, F View FIGURE 18 ; 19A View FIGURE 19 ) or in published illustrations and photographs ( Rathbun 1918: fig. 7 a; Guinot 1969b: fig. 3; Williams 1984: fig. 344 for F. hirsuta , and A. Milne-Edwards & Bouvier 1923: pl. 6, fig. 1; Rathbun 1918: pl. 4, fig. 1 Guinot 1969b: fig. 2 for F. barbata ). A. Milne-Edwards & Bouvier (1923: 337), in the detailed descriptions of F. barbata and F. rosaea , which were briefly described but not illustrated by A. Milne-Edwards (1880b), refer to the differences between the two species as very slight (differences très légères). Only one character separates them, the presence in F. rosaea of a “tuberculiform swelling” (un petit renflement tuberculiforme) between the outer orbital tooth and the anterolateral tooth on each side of the carapace. Such a feature, which was the only character used in Rathbun’s key to separate between the two species, is apparent as a short tooth in the figure in A. Milne-Edwards & Bouvier (1923: pl. 6, fig. 1) but it was not found in the male holotype (MNHN-B8733).

Characteristic of F. hirsuta is the variously long and dense tomentum on the anterior portion of the cheliped propodus and the anterior margin of cheliped carpus ( Rathbun 1918: fig. 7; Guinot, 1969b: pl. 2, fig. 3; Williams 1984: fig. 344), a character present in the type material ( Fig. 18E, F View FIGURE 18 ). Long tufts of tomentum are also present on the inner margin of the carpus. A tomentum is also present, although presumably shorter, in F. barbata (A. Milne-Edwards & Bouvier 1923: pl. 6, fig. 2; Rathbun 1918: pl. 4, fig. 1, 3). The length of the tomentum, and even its presence, is a variable character among many species of euryplacids so the use of this to separate species is questionable. The collection of additional material, particularly of F.rosaea , should clarify the status of all three putative species of Frevillea . As such, no diagnoses are given below for each of the three species of Frevillea given the ambiguous character of their supposed diagnostic characters.

A fourth species, described as F. tridentata A. Milne-Edwards, 1880 , is now included, as Trapezioplax tridentata , in the Pseudorhombilidae Alcock, 1900 (see Guinot 1969b: 514; Ng et al. 2008: 192). The dorsal surface of this species is almost identical to that of Frevillea (as well as of Goneplax and other genera of Goneplacidae ) but its abdomen and gonopods clearly indicate that it is a pseudorhombilid and not a euryplacid.

Species included.

Frevillea barbata A. Milne-Edwards, 1880

Frevillea hirsuta ( Borradaile, 1916)

Frevillea rosaea A. Milne-Edwards, 1880

The genus is restricted to the Western Atlantic region.