Euphrosynoplax dincao, Tavares & Santana, 2021

Tavares, Marcos & Santana, William, 2021, First record and a new species of Euphrosynoplax (Crustacea: Pseudorhombilidae) from the southwestern Atlantic, Papéis Avulsos de Zoologia (Pap. Avulsos Zool., S. Paulo) 61, pp. 1-7 : 1-7

publication ID 10.11606/1807-0205/2021.61.66

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Euphrosynoplax dincao

sp. nov.

Euphrosynoplax dincao View in CoL sp. nov.

( Figs. 1 View Figure 1 A-E; 2A, B; 3A, D, F)

Type material: Brazil: holotype male, cl 48.5 mm, cw 54 mm ( MZUSP 25998), F/ V “Daniela Moura I”, stn 21, 27°45′07.2″S / 47°47′13.2″W, off the coast of Florianópolis, Santa Catarina, 19.iv.2008, bot- tom tangle net, 123 m. 1 ovigerous female paratype cl 22.8 mm, cw 31 mm ( MZUSP 41475), same data as holotype.

Comparative material: Euphrosynoplax clausa : USA: holotype male, cl 24 mm, cw 33 mm ( USNM 65938), Gulf of Mexico, Florida Keys, Dry Tortugas, south of Loggerhead Key, Tortugas Expedition Carnegie Laboratory, 24°40′12.0″N / 81°34′48.0″W,W.L.Schmitt coll. 07.viii. 1931, 91 m. 1 female ( USNM 250197), Gulf of Mexico, R / V “Success”, stn 23, from 29°44′55″N / 87°11′53″W to 29°48′58″N / 87°02′35″W, F. Hubbard coll. 19.iv.1989. Euphrosynoplax campechiensis : USA: 1 male ( USNM 298320), northern part of Gulf of Mexico, R / V “ Oregon II”, Cruise 210, stn 74, summer 1994. Caribbean Sea: 1 male ( USNM 267608), between Saint Kitts and Nevis, R / V “ Oregon II”, stn 10843, 17°06′00.0″N /62°316′48.0″W, U.S. Fish and Wildlife Service coll. 08.xii. 1969, 589 m. 1 female ( MZUSP 29592), Guadeloupe, Mission ORSTOM-IRPM-SMCB, stn C32, west coast of Basse Terre, 16°21.34′N / 61°49.14′W, G. Leblond and J. Poupin coll. iv. 1993, 350 m [J. Poupin don.].

Description of the holotype: Carapace ( Fig. 1 View Figure 1 A-C; 2A, B) distinctly wider than long, maximal width at third anterolateral tooth, coarsely granular near anterolateral margins and frontal region, finely granulated posteriorly, central parts of carapace scarcely granulated. Carapace regions well marked.Ventrally, granulation neatly more distinct on suborbital, subhepatic, pterygostomial and branchiostegal regions. Pterygostomian region granular near dehiscense line and near mxp3. Branchiostegal region granular,pubescent. Fronto-orbital width little less than half of maximal width of carapace; frontal margin V-shape clefted medially; frontal margin coarsely crenulated; region behind frontal margin coarsely tuberculated.Supraorbital margin coarsely crenulated, interrupted by 2 distinct notches. Inner supraorbital tooth separated from front by wide,smooth,shallow gap; tooth broad triangular, coarsely tuberculated, blunt. Outer supraorbital tooth lobe-like, coarsely tuberculated. Suborbital margin lined with large tubercles, mesially with triangular, coarsely tuberculated tooth directed toward front, laterally with rounded lobe, V-shape notch between suborbital lateral lobe and outer orbital tooth. Anterolateral margin projecting in 4 coarsely tubercular teeth (outer orbital excluded), increasing in size posteriorly from first to third tooth. First tooth straight,blunt; second largest, broad triangular, blunt, slightly curved forward; third curved forward;fourth spiniform.Gap between anterolateral teeth2-3 distinctly wider than between teeth 1-2, 3-4. Posterolateral margin well defined,rather straight behind last anterolateral tooth, distinctly longer than anterolateral margin. Limit between epistome, endostome well defined, forming pronounced, sinuous lip, interrupted by 2 V-shaped notches, one at each side of shallow mesial notch.

Ocular peduncle ( Fig. 1C View Figure 1 ) coarsely granular dorsally, freely movable, thick, fully retractable into large orbital cavity; cornea occupying little less than one-third of whole eye, brownish, ommatidia well recognizable.

Antennules prominent; basal article thickest laterally, with transverse row of coarse granules; second article smooth, elongate, subcylindrical, articulated to basal article at mesial end of antennular fossa; third article nearly equal in length to second, swollen distally, tapered to proximal articulation with second article, terminally with long stiff setae.

Antennal article 2+3 immovable, filling orbital gap between strong, acute, inner orbital tooth and front; articles 4, 5 freely movable, subcylindrical. Thoracic sternum densely,evenly granular; lateral margins of sternites 2 to 4 coarsely granular. Sterno-pleonal cavity remarkably deep at level of sternites 4 to 6, pilose,smooth anteriorly, lateral margins granular. Pleonal locking system functional, thoracic sternal button small, directed forward, placed about mid-length between thoracic sternal sutures 4/5 and 5/6.

Third maxillipeds (exopod included) ( Fig. 1B, C View Figure 1 ) densely, evenly granular, granules larger near margins; palp finely granular.

Chelipeds heterochelous ( Fig. 1D, E View Figure 1 ), left P1 strongest. Merus of major P1 trigonal, dorsal margin with row of spiny tubercles; lateral and ventral surfaces evenly covered with minute granules, and few scattered larger tubercles. Carpus with strong, blunt spine on inner margin; surfaces coarsely tubercular, tubercles of different sizes, spiny. Propodus stout, surfaces minutely granular. Fingers massive, gently curved inward, closing terminally only; cutting edges bluntly dentate, teeth of different sizes. Minor cheliped similar to major cheliped except for its less sout propodus and slender fingers.

Ambulatory legs ( Fig. 1A, B View Figure 1 ), pubescent, rather, massive, similar to each other. Meri of P2-P5 spinulous dorsally and ventrally, granular laterally and mesially. Carpi of P2-P5 coarsely granular dorsally, otherwise smooth. Propodi of P2-P4 with scattered granular proximally; P5 propodus scattered granular dorsally. Dactyli of P2-P5 corneous-tipped, dorsal, ventral, lateral and mesial sides each with 2 longitudinal rows of long setae.

Pleon of 4 pleonites and telson.Pleonites 1-2 markedly shorts, coarsely granular, pubescent. Pleonite 1 slightly broader than pleonite 2. Pleonites 3-5 fused together; third coarsely granular proximally only, expanded laterally, covering penis. Pleonites 4-6 and telson rather smooth. Pleonal suture 3/4 faint, still recognizable laterally; sutures 4/5 and 5/6 indistinct. Pleonite 6 expanded anterolaterally. Telson semicircular.

G1 ( Fig. 3A, D View Figure 3 ) curved towards inside sterno-pleonal cavity, slightly overreaching thoracic sternal suture 4/5; distal end with V-shaped, large lobe on sternal side. G2 ( Fig. 3F View Figure 3 ) very short, about 1/4 of the length of G1, strongly curved, tapering distally, ending in acute tip.

Female paratype resembling male, although much smaller. Pleon of 6 free, narrow pleonites and telson. Pleonites 1 to 5 of about same width and length; sixth pleonite almost twice as long previous pleonites. The paratype female carried numerous small eggs.

Etymology: We take great pleasure in naming this new species after our esteemed colleague and friend Fernando D’Incao (1947-2016), carcinologist and oceanographer at Universidade Federal do Rio Grande, Brazil. The specific name is used as a name in apposition.

Remarks: Euphrosynoplax consists so far of two species, both currently known from the Gulf of Mexico, namely E. clausa and E. campechiensis ( Guinot, 1969; Vázquez-Bader & Gracia, 1991; Felder et al., 2009). Euphrosynoplax campechiensis is herein recorded for the first time from the Caribbean Sea (Guadeloupe and between Saint Kitts and Nevis- see above under material examined).

Euphrosynoplax dincao sp. nov. ( Fig. 1 View Figure 1 A-E; 2A, B; 3A, D, F) can be easily distinguished from the above two species in that the distal end of the male P5 merus falls short of the last (fourth) anterolateral carapace tooth or reaches to the base of the tooth at most, whereas in the northern counterparts the distal end of the male P5 merus extends almost to the tip of the last anterolateral carapace tooth ( Fig. 2 View Figure2 A-F). The three species also differ in the shape of the mesial lobe and development of the apical lobe of the G1 ( Fig. 3 View Figure 3 A-E).

The new species is morphologically closer to E. campechiensis ( Fig. 2C, D View Figure2 ; 3B, E View Figure 3 ; 4 View Figure 4 A-D) of which it further differs in having the anterolateral teeth and anterolateral, pterygostomial and branchiostegal regions much more densely and coarsely tuberculated; the carapace front prominently protruded in ventral view (vs front distinctly less protruded in ventral view in E. campechiensis ); and the area behind the supraorbital margin distinctly granular, devoid of tiny pubescence (vs area behind the supraorbital margin devoid of granules and with tiny pubescence in E. campechiensis ).

Euphrosynoplax dincao sp. nov. additionally stands apart from E. clausa ( Fig. 2 View Figure2 E-F; 3C; 5A-D) in having the carapace and appendages unevenly tubercular with tubercles of different sizes (vs carapace and appendages more evenly and finely granular); carapace regions well marked (vs carapace regions faintly marked in E. clausa ); last (fourth) anterolateral tooth large and more laterally directed (vs last carapace tooth much smaller and more forward directed in E. clausa ); orbits, almost completely filled by the ocular peduncle, orbital cavity smooth (vs orbits distinctly larger than the ocular peduncle, upper region inside the orbital cavity granular in E. clausa ); and the frontal margin, bilobed, V-shaped incised, each lobe with a lateral prominence (vs frontal margin much less prominent, U-shaped incised, each lobe only gently prominent laterally in E. clausa ).

The north-south disjunct distribution pattern of Euphrosynoplax is highly comparable to those of other moderately deep-water decapods, such as Eumunida , Neopilumnoplax , Robertsella , Speocarcinus and Trichopeltarion (Brandão et al., 2010, 2012; Tavares & Melo 2005, 2010; Tavares & Gouvea, 2013; Tavares & Lima 2019). Such distribution gaps may well be only the result of poor distributional information and detectability, as exemplified by the deep-water genus Chaceon , whose fragmented distribution of some of its southwestern Atlantic representatives has been slowly filled as a result of the intensification of deep-water commercial fishing and detection facilitated by the species’ large size ( Manning & Holthuis, 1989; Manning et al., 1989; Tavares & Pinheiro, 2011).


Museu de Zoologia da Universidade de Sao Paulo


Royal British Columbia Museum - Herbarium


Smithsonian Institution, National Museum of Natural History


Departamento de Geologia, Universidad de Chile

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