Salmoneus rocas , Anker, Arthur, 2007

Anker, Arthur, 2007, New species and records of alpheid shrimps, genera Salmoneus Holthuis and Parabetaeus Coutière, from the tropical western Atlantic (Decapoda, Caridea), Zootaxa 1653, pp. 21-39: 29-30

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Salmoneus rocas

n. sp.

Salmoneus rocas  n. sp.

Fig. 4View FIGURE 4

Material examined: Holotype: ovig. female, MNRJAbout MNRJ 20216, Brazil, Atol das Rocas  , east of Laguna Interna, in calcareous alga, depth 1 m, coll. F.B. Pitombo and R. Barroso, 18 Oct 2000 [dissected].

Description: Carapace not setose, with numerous minute pits ( Fig. 4View FIGURE 4 a–d). Rostrum much longer than broad; slightly overreaching distal margin of second segment of antennular peduncle ( Fig. 4View FIGURE 4 a, b); lateral margins slightly convace proximally; ventral margin unarmed ( Fig. 4View FIGURE 4 b, c); rostral carina distinct, reaching beyond eyes posteriorly ( Fig. 4View FIGURE 4 a). Orbital spines large, acute, slightly mesially directed ( Fig. 4View FIGURE 4 a). Pterygostomial margin slightly protruding anteriorly, broadly rounded ( Fig. 4View FIGURE 4 b–d). Eyes covered in dorsal view, visible in lateral view ( Fig. 4View FIGURE 4 a–d). Antennule with stylocerite distinctly overreaching distal margin of second segment of antennular peduncle, with acute tip; second segment about 0.7 times as long as wide ( Fig. 4View FIGURE 4 a). Antenna with basicerite bearing subacute distoventral spine ( Fig. 4View FIGURE 4 b); scaphocerite ovate, distolateral spine small, subacute ( Fig. 4View FIGURE 4 a). Third maxilliped with rounded lateral plate; ultimate segment with tapering tip, without distinct spiniform setae ( Fig. 4View FIGURE 4 j). Chelipeds strongly asymmetrical in shape, unequal in size ( Fig. 4View FIGURE 4 k–m). Major cheliped ( Fig. 4View FIGURE 4 k, l) with unarmed ischium; merus not inflated distally, ventral surface somewhat depressed; carpus cupshaped, ventrally not depressed, distally with rounded lobes ( Fig. 4View FIGURE 4 k); chela mostly smooth, subcylindrical, not depressed ventrally, not flattened mesially, with deep groove proximoventrally ( Fig. 4View FIGURE 4 k); fingers subequal to palm, cutting edges serrated, with 11 subtriangular-rounded teeth, distal teeth larger ( Fig. 4View FIGURE 4 l). Minor cheliped ( Fig. 4View FIGURE 4 m) with ischium subequal to merus, both unarmed; carpus slightly shorter than merus; chela small, simple, with fingers subequal to palm. Second pereiopod Fig. 4View FIGURE 4 n) with unarmed ischium; carpus bearing five segments, first segment subequal to sum of other four segments. Third pereiopod ( Fig. 4View FIGURE 4 o, p) with ischium bearing one ventrolateral spiniform seta; merus about four times as long as wide; carpus distally with small ventral spiniform seta; propodus with four small ventral spiniform setae, including distal seta; dactylus simple, conical, moderately slender, less than half length of propodus. Fifth abdominal somite with subacute posteroventral angle ( Fig. 4View FIGURE 4 e). Sixth abdominal somite without distinct articulated plate, with acute posteroventral projection ( Fig. 4View FIGURE 4 e); preanal plate acutely produced towards telson ( Fig. 4View FIGURE 4 f). Second pleopod with appendix masculina shorter than appendix interna, furnished with slender spiniform setae on apex and along outer margin ( Fig. 4View FIGURE 4 h). Uropod with with sinuous diaersis and relatively stout distolateral spiniform seta ( Fig. 4View FIGURE 4 e). Telson about 1.7 times as long as wide proximally, tapering posteriorly, with two pairs of dorsal spines, inserted at about mid-length and 2 / 3 telson length, respectively ( Fig. 4View FIGURE 4 g); posterior margin with subtriangular median notch and two pairs of spiniform setae at posterolateral angles, mesial setae distinctly longer than lateral setae ( Fig. 4View FIGURE 4 g). Gill/exopod formula typical for genus (see under S. ortmanni  ).

Colour: Unknown.

Size: Holotype: CL 3.8 mm, TL 11.6 mm.

Etymology: The new species is named after the type locality, Atol das Rocas  off the northeastern coast of Brazil.

Ecology: The holotype was found in a crust of calcareous algae, in 1 m deep water.

Type locality: Atol das Rocas  , Brazil.

Distribution: Western Atlantic: presently known only from the type locality, Atol das Rocas  .

Remarks: The new species appears to be related to S. arubae ( Schmitt, 1936)  from the western Atlantic; S. teres Manning & Chace, 1990  , S. setosus Manning & Chace, 1990  , both from the western and central Atlantic (see below); and S. serratidigitus (Coutière, 1896)  from the Indo-Pacific. It can be separated from S. arubae  and S. teres  by the very different shape of the frontal margin of the carapace (cf. Schmitt, 1936: fig 2 a; Manning & Chace, 1990: fig. 10 b); from S. arubae  by the presence of a posteromedian notch on the telson (absent in S. arubae  ; cf. Schmitt, 1936: fig. 2g); from S. setosus  by the absence of conspicuous thickened setae on the carapace, abdomen and telson (a diagnostic feature of S. setosus  ; cf. Manning & Chace, 1990: fig. 9 a, b; see also Fig. 6View FIGURE 6 a, b); from S. serratidigitus  by the ischium of the third pereiopod bearing one spiniform seta (vs. two or three setae in S. serratidigitus  ), and the subtriangular median notch on the posterior margin of the telson (vs. U-shaped in S. serratidigitus  ; cf. Banner & Banner, 1981: fig. 8). The present evidence suggests that S. rocas  n. sp. is most closely related to S. serratidigitus  from the Indo-Pacific and may represent the S. serratidigitus  species complex in the western Atlantic.

The minute pits on the carapace are present in S. rocas  n. sp., but also in S. cf. arubae  (cf. Holthuis, 1990) and S. teres  (R. Lemaitre, pers. comm.; see also below), and may be an important taxonomic and phylogenetic character within the S. serratidigutus  species group ( Anker & Marin, 2006).


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