Machaerus atlanticus ( Miers, 1881 )

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 77-78

Machaerus atlanticus ( Miers, 1881)

( Figs. 29A–D ; 32A, B )

Pilumnoplax sulcatifrons var. atlantica Miers, 1881: 259 , 375 [in list; Senegal]; 1886: 226 [in list].

Pilumnoplax atlantica — Monod 1956: 340 [in key], 341, figs. 442—449 [ Senegal, Guinea, Sierra Leone]. — Forest & Guinot 1966: 85 [ Guinea, Ghana, Nigeria]. — Crosnier 1969: 531 [Congo-RC]. — Guinot 1969b: 517, 518 [discussion] [ Senegal]; 1969c: 688; 1971: 1081 [in list]. — d’Udekem d’Acoz 1999: 242 [in list] [references].

“ Pilumnoplax ” atlantica — Guinot 1969b: 507, 508 [discussion], figs. 36, 53.

[ Pilumnoplax ] atlantica — Guinot 1971: 1081 [in list].

Machaerus atlanticus — Manning & Holthuis 1981: 162 [references] [ Ivory Coast, Ghana]. — Ng et al. 2008: 78 [in list].

not Pilumnoplax atlantica — Balss 1922b: 76 [ Liberia, Ivory Coast, Equatorial Guinea]. — Monod 1933: 533, fig. 19A, 20, 21E [ Mauritania]. — Capart 1951: 166, fig. 63 [ Gabon, Cabinda, Congo-RC]. [= Machaerus oxyacanthus ( Monod, 1956) ]

Type material. Unknown status (not MNHN) .

Type locality. Senegal, Gorée I.

Material examined. Mauritania. M. Monod coll., 1923, id. as Pilumnoplax atlantica by M. Monod: 1 male ( MNHN-B10237 ) .

Senegal. Gorée I., Marche-Marchand coll., 09.01.1951: 1 ovigerous female, 6.0 mm × 8.2 mm (MNHN- B10239). – Joal, 10–11 m, 20.02.1953: 1 male 8.2 mm × 10.9 mm ( MNHN-B10240 ); 4 m, 19.02.1953: 2 males, 6.5 mm × 8.9 mm, 6.5 mm × 9.0 mm ( MNHN-B 10238 ) .

Guinea. Calypso , stn. 7, 18 m, 17.05.1956: 2 males, 2 pre-adult females ( MNHN-B10233 ) .

Diagnosis. Anterolateral teeth, outer orbital teeth about same size, shape, second tooth only slightly longer than the first, third ( Fig. 29A, B ).

Remarks. Machaerus atlanticus appears to be sympatric with its only known congener, M. oxyacanthus . Both species can be easily differentiated from each other by the morphology of the anterolateral teeth. All three anterolateral teeth and the outer orbital teeth are about the same size and shape in M. atlanticus , with the second tooth only slightly longer than the first and third ( Fig. 29A, B ). The anterolateral teeth of M. oxyacanthus are acute, different from the triangular outer orbital teeth, and the second anterolateral teeth much longer and more elevated than the first ( Fig. 30A, B ). Monod (1956: 345) provided some colour notes of a freshly preserved specimen, and there are some apparent differences between its colour pattern and that of M. atlanticus (see Manning & Holthuis 1981: 163).

Distribution. Atlantic coast of Africa from Senegal to Congo (RC). Depth: 4–100 m ( Manning & Holthuis 1981).

Figures

FIGURE 29. Machaerus atlanticus (Miers, 1881); A, B, male (6.5 mm × 8.9 mm) (MNHN-B 10238), Senegal, Joal; C, D, ovigerous female (6.0 mm × 8.2 mm) (MNHN-B10239), Senegal. Gorée I. A, C, overall views; B, anterior portion of male thoracic sternum and abdomen; D, female thoracic sternum and vulvae. Abbreviations: s4–s6 = thoracic sternites 4 to 6, respectively; v = vulva.

FIGURE 30. Machaerus oxyacanthus (Monod, 1956); male (19.0 mm × 30.3 mm) (MNHN-B10242), Sierra Leone. A, overall view; B, frontal view showing orbits and antennae; C, third maxillipeds; D, outer surface of left chela; E, male thoracic sternum and abdomen; F, male sterno-abdominal cavity, G1, and penis; G, posterior portion of male thoracic sternum and abdomen. Abbreviations: a1–a3 = male abdominal somites 1, 2, 3, respectively; cx5 = coxa of fifth pereopod (P5); es7 = episternite 7; G1 = first male pleopod; G2 = second male pleopod; g = male gonopore; p = penis; s4–s8 = thoracic sternites 4 to 8, respectively.

FIGURE 32. A, B, Machaerus atlanticus (Miers, 1881) (after Guinot 1969b: figs. 36, 53, as “Pilumnoplax” atlantica); C–F, Machaerus oxyacanthus (Monod, 1956) (after Guinot 1969b: figs. 38, 54a, 54b, 55, as “Pilumnoplax” oxyacantha); G–K, Nancyplax vossi Lemaitre, García-Gómez, von Sternberg & Campos, 2001 (after Lemaitre et al. 2001: figs. 5b–e). A, C, posterior portion of male thoracic sternum, abdomen, and gonopore; B, D, E, H, I, G1; F, J, K, G2. Abbreviation: a1–a3 = male abdominal somites 1, 2, 3, respectively; g = male gonopore.