Pilumnoidea, Samouelle, 1819

GUINOT, DANIÈLE, TAVARES, MARCOS & CASTRO, PETER, 2013, Significance of the sexual openings and supplementary structures on the phylogeny of brachyuran crabs (Crustacea, Decapoda, Brachyura), with new nomina for higher-ranked podotreme taxa, Zootaxa 3665 (1), pp. 1-414 : 133-134

Superfamily Pilumnoidea

The male gonopore is coxal. The penis condition can be either coxal (plesiomorphic condition) or coxo-sternal (derived condition in Rhizopidae ).

The Eumedonidae and Rhizopidae are treated here as full families in contrast to Ng, Guinot & Davie (2008: 138, 143) (see Coxo-sternal condition). The pilumnoid penis emerges either from the extremity of the P5 coxosternal condyle or from its anterior margin, sometimes at the limit between the condyle and the coxa itself as in Actumnus ( Guinot 1979a: fig. 49) and Rhizopidae ( Fig. 8J ) (see Modalities of penis protection: Condylar protection). These modalities of condylar protection could be regarded as synapomorphies for the Pilumnoidea .

Family Eumedonidae . The male gonopore is coxal. The penis emerges as a wide, short, and soft papilla from a large gonopore located at the extremity (approximately) of the P5 coxo-sternal condyle (e.g., Eumedonus brevirhynchus , Echinoecus pentagonus ) on its anterior margin (e.g., Harrovia longipes , Ceratocarcinus longimanus ), the condylar margin posteriorly articulating on sternite 8 (see Modalities of penis protection: Condylar protection).

Family Galenidae . The male gonopore is coxal in Galenidae Alcock, 1898 . In Halimede De Haan, 1835 (Halimedinae Alcock, 1898), the penis emerges from the extremity of the coxo-sternal condyle ( Guinot 1979a: figs. 24C, 50A; see also Guinot 1969d; Tesch 1918b; Takeda & Miyake 1969; Serène 1971; Takeda 1972; Türkay 1978, 1983c; Davie 2002; Poupin 2010). In Galene a thick, long penis also emerges from the extremity of the P5 coxo-sternal condyle, which is wedged between episternite 7 and an extension of sternite 8; a fold at the base of the condyle articulates with the small gynglyme of sternite 8 ( Guinot 1979a: fig. 50B; Tavares 1992a: fig. 1D).

Family Pilumnidae . The male gonopore is coxal. In Pilumnus ( Fig. 8E ; Duvernoy 1853: 152, pl. 3/4, fig. 15), Vellumnus labyrinthicus (Miers 1884) (Ng 2010: fig. 19B), and Pilumnopeus A. Milne-Edwards, 1867 ( Bouvier 1940: fig. 166C), the penis emerges close to the extremity of the P5 coxo-sternal condyle or at its extremity. The condyle articulates on sternite 8 by the more basal portion of its inner margin, which appears bilobed thanks to a distinct notch at the edge. A similar pattern characterises all pilumnids.

Family Rhizopidae . The Rhizopidae displays an exclusively coxo-sternal condition, the posterior sternites being always broad. In Rhizopa gracilipes ( Fig. 8I ) the penis, which emerges from the anterior margin of the P5 coxo-sternal condyle at the limit of the condyle with the coxa (see Modalities of penis protection: Condylar protection), is sheltered in a long gutter on sternite 8 (as in Fig. 14 ) and ends into a long soft papilla at the point where sternites 7 and 8 separate from each other. The disposition is the same in the few other rhizopids examined, but in Cryptolutea granulosa (McGilchrist, 1905) and in some species of Typhlocarcinops Rathbun, 1909 , sternites 7 and 8 may not be completely joined so the penis is partially exposed, with the same arrangement as that shown in Fig. 8J . We agree with Ng (1987a: 105) who wrote in a revision of Rhizopinae (at that time consisting of 20 genera and 74 species): “The Rhizopinae still cannot be properly defined, and important characters like the position of the male genital openings are still unknown for many taxa”. The penial configuration thus needs to be reviewed in all rhizopid genera and species.

The status of the fossil Rhizopidae ( Feldmann et al. 2005: 442) remains uncertain, the recovery of a ventral surface being probably insufficient (as it is for living forms), the best character for the identification of these pilumnoid crabs with broad posterior sternites being the shape of the G1 (recurved) and G2 (sigmoid).

Figures

FIGURE 8. Coxal gonopore in heterotreme families, including families with coxo-sternal condition (D, G, I–K). A, Corystes cassivelaunus (Pennant, 1777) (Corystidae), male 33.0 × 26.0 mm, Bay of Biscay, (MNHN-B27912); B, Thia scutellata (Fabricius, 1793) (Thiidae Thiinae), male 17.7 × 19.0 mm, Mediterranean Sea (MNHN-B416); C, Xantho hydrophilus (Herbst, 1790) (Xanthidae Xanthinae), male 20.5 × 33.0 mm, France, Concarneau; D, Goneplax rhomboides (Linnaeus, 1758) (Goneplacidae Goneplacinae), male 12.0 × 21.0 mm, Tunisia (MNHN-B10159); E, Pilumnus hirtellus (Linnaeus, 1761) (Pilumnidae Pilumninae), male, Mediterranean Sea (MNHN); F, Menippe mercenaria (Say, 1818) (Menippidae), male, Florida (MNHN-B9500); G, Ommatocarcinus macgillivrayi White, 1851 (Goneplacidae Goneplacinae), male 27.7 × 73.6, Australia, New South Wales (MNHN-B10216); H, Bythograea thermydron Williams, 1980 (Bythograeidae), male 33.0 × 60.0 mm, paratype, Galapagos Rift (MNHN-B6468); I, Rhizopa gracilipes Stimpson, 1858 (Pilumnoidea Rhizopidae), male 6.3 × 8.8 mm, Thailand (MNHN-B24500); J, Malacoplax californiensis (Lockington, 1877) (Panopeidae), male 10.0 × 14.0 mm, Gulf of California (MNHN-B10212); K, Prionoplax spinicarpus H. Milne Edwards, 1852 (Panopeidae), male 14.8 × 22.2 mm, holotype, [? China: erroneous origin] (MNHN-B10347). In E, F, penis emerging from P5 coxo-sternal condyle. a1, a3, abdominal somites 1, 3; c, coxo-sternal condyle; cx5, P5 coxa; e7, episternite 7; g, gonopore; m.l., median line; p, penis; 7, 8, thoracic sternites 7, 8; 6/7, 7/8, thoracic sternal sutures 6/7, 7/8.

FIGURE 14. Derived coxo-sternal condition showing penis sheltered in gutter and location of “supplementary” suture 7/8 at complete dorsal junction of sternites 7 and 8 (both separated here to expose penis), “true” suture 7/8 situated below. Prionoplax ciliata Smith, 1870 (Panopeidae Eucratopsinae), male 13.4 × 20.3 mm, Panamá (MNHN-B24490). cx4, cx5, P4, P5 coxae; g, gutter; p, penis; pa, papilla; 7, 8, thoracic sternites 7, 8; 6/7, 7/8, thoracic sternal sutures 6/7, 7/8. Scale bar: 2 mm.