Goneplacoidea, MacLeay, 1838

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 : 111-118

Superfamily Goneplacoidea

Family Acidopsidae . The male gonopore is coxal. Acidops cessacii shows a typical coxal condition. A large, thick, muscular penis emerges from the large gonopore located above the P5 coxo-sternal condyle and lies in a shallow depression on sternite 8 at the suture 7/8 level (A. Milne-Edwards & Bouvier 1900: 78); the abdominal somite 3, transversally elongated, covers the penis.

Acidops Stimpson, 1871 , monotypic, was assigned to Pilumnidae ( Balss 1921) , Xanthidae (Rathbun 1930) , Rhizopinae Stimpson, 1858 ( Balss 1957; Melo 1996), Goneplacidae ( Tesch 1917, as Epimelus A. Milne-Edwards, 1878; Monod 1956; Guinot & Ribeiro 1962; Ng 1987a; Manning & Chace 1990; see also Barreto et al. 1993; Tavares & Mendonça 2004), Chasmocarcininae Serène, 1964 ( Ng 2002), to its own family and superfamily ( Števčić 2005: 36, as Acidopidae [sic], Acidopoidea [sic]), and to Acidopsidae in the Goneplacoidea ( Ng, Guinot & Davie 2008; De Grave et al. 2009: 32; Castro et al. 2010: table 1).

As the diagnosis in Števčić (2005) is incomplete, some comments on the morphology of the Acidopsidae are in order. Instead of being a derived heterotreme as implied by its previous assignment to Chasmocarcinidae , the Acidopsidae shows the following plesiomorphic characters: male gonopore coxal, with a trend towards coxosternal condition; thoracic sternum narrow and elongated; sternite 3 only slightly enlarged transversally; sternal sutures 4/5–7/8 complete, equidistant, nearly horizontal, suture 2/3 also complete, 3/4 extremely short, only lateral; sternite 8 reduced, with only a small portion dorsally visible; presence of a long median line, reaching sternite 4; six abdominal somites, 3–5 fused but only ankylosed and with sutures still distinct, even medially (A. Milne- Edwards & Bouvier 1900: pl. 15, fig. 8; Ng 2002: 212; Castro et al. 2010: table 1), and somites 1 and 2 in a dorsal position; G1 with long protopodite; G2 long, as long as the G1, with long flagellum ( Guinot & Ribeiro 1962: figs. 27, 28); homochely and homodonty. Consequently, Acidops is a basal heterotreme, but with the anterior sternites 1–3 not extended in the form of a developed triangle.

Parapilumnus Kossmann, 1877 , with its type species P. cristimanus (see Ng & Chen 2004) and the related species P. oryctos Ng, 2002 , also shows a trend towards coxo-sternal conditon, with the thick penis in a slight depression ( Ng 2002: 212, 219, fig. 8d). Parapilumnus shares with Acidops most of its plesiomorphic characters, including a straight, stout G1 and an elongated G2 ( Ng 2002: fig. 8E–H, for Parapilumnus ). Both genera share a vulva mostly covered by an operculum. Some characters are, however distinctive, including the male abdomen with fused abdominal somites 3–5 and relatively narrow abdominal somite 3 in Parapilumnus (somites 3–5 ankylosed and abdominal somite 3 transversally elongated in Acidops ), as well as the location of the press-button for abdominal locking (slightly far from suture 5/ 6 in Acidops , practically above suture 5/ 6 in P. oryctos , see Ng 2002: fig. 8B).

The taxonomic history of Parapilumnus is complicated (see review by Ng 2002). Rathbun (1930a) regarded it as a synonym of Pilumnus Leach, 1816 . Its type species P. cristimanus (see Ng & Richer de Forges 2007) was transferred to Globopilumnus Balss, 1933 ( Balss 1933) , but subsequently excluded from it ( Guinot-Dumortier 1961). Parapilumnus was eventually referred to the Chasmocarcininae ( Ng 2002) , then placed in its own family and superfamily, Parapilumnidae and Parapilumnoidea Števčić, 2005 ( Števčić 2005), and more recently included in Acidopsidae ( Ng, Guinot & Davie 2008; Castro et al. 2010). Parapilumnidae Števčić, 2005 , is a junior synonym of Acidopsidae Števčić, 2005 .

Family Chasmocarcinidae . The male gonopore is coxal, located just above the P5 coxo-sternal condyle. The sternite 8 is invaginated into a channel, a penial groove (“genital groove” or “penial channel” of some authors) in which the long penis (proximal portion excepted) is concealed being enclosed within the invagination formed by sternite 8 posterior to suture 7/8, instead of along the sternal suture 7/8 ( Fig. 24 ); sternite 7 is prolonged posteriorly forming a long episternite 7 bordering the anterior half of sternite 8 ( Fig. 8I–K ; see Modalities of penis protection: Protection by invagination of the penis into sternite 8). The terminal papilla emerges from sternite 8, thus representing a coxo-sternal condition. As the line of invagination is clearly visible, close and parallel to thoracic sternal suture 7/8, the wide sternite 8 seems to be subdivided transversally into two parts, giving the false impression of a double or supplementary plate inserted between sternites 7 and 8. This double plate has been called “intercalated plate”, “interplate”, “supplemental sternal plate”, “supplementary plate”, “supplementary accessory plate”, “genital covering plate”, “coxo-sternal plate”, “penian channel”, or “invaginated channel” ( Rathbun 1914; Felder & Rabalais 1986: figs. 2d, 5d; Guinot 1986: pl. 2, figs. C, D; Davie 1988: fig. 1F; Tavares 1992a: figs. 1A, 2C–D; Blow & Bailey 1992: 175, pl. 1, figs. 1b, 5, 7, pl. 2, fig. 7; Davie & Guinot 1996: figs. 3G, 7; Coelho Filho & Coelho 1998: 804, 809, 812, figs. 4a, 7a, b; Schweitzer & Feldmann 2001a: 338, 339; Karasawa & Kato 2003a, b; Števčić 2005: 107, 108; Castro et al. 2010: table 1). The “supplementary plate” is nothing but the invaginated sternite 8 for penis protection. The sternite 8 of chasmocarcinid females is evidently not invaginated and shows as a normal, single plate.

In Chasmocarcinus typicus , the penis is typically completely enclosed by sternite 8. In a few individuals, however, the margins of the penial groove do not join completely, so the penis is partially visible ( Blow & Bailey 1992: pl. 1, fig. 1b). In C. cylindricus , the penial groove is only partially closed, so that the distal half of the penis is exposed. An “open suture in sternite 8, such that the penis is visible” was mentioned in Hephthopelta sp. ( Davie & Guinot 1996: 285), whereas the penial groove is completely closed in our material of Hephthopelta bruuni . According to Komai et al. (2012: 141, 148, fig. 7D) the supplementary sternal plate of some species of Hephthopelta Alcock, 1899 , such as H. cf. lugubris Alcock, 1899 , is “actually not a well-defined plate and is partially mobile” and the penis is strongly calcified. The supplementary plate of Camatopsis rubida illustrated by Hsueh & Huang (2002: fig. 1D) and Komai et al. (2012: 148, fig. 6C) occupies “all the way across the thoracic sternum”.

In Raoulia Ng, 1987 ( Ng 1987a: 93) , the penis, which lies in a long groove between sternites 7 and 8 and has its exposed dorsal surface sclerotised, is slightly mobile (P.K.L. Ng, pers. comm. 2012; see also Komai et al. 2012: 141). The placement of Raoulia in the Chasmocarcinidae was considered doubtful by Ng, Guinot & Davie (2008: 76, note 1) because there is no “supplementary plate”, as shown by Barnard (1955: fig. 16, as Typhlocarcinodes piroculatus ). Thus, Raoulia is tentatively excluded here from Chasmocarcinidae . Števčić (2005: 71) assigned Raoulia to its own superfamily without mentioning the male genital region as did previous authors such as Tesch (1918b: 231, incorrectly as T. piroculatus Rathbun, 1911 ), Serène (1964a: 237, incorrectly as T. piroculatus ), and Ng (1987a) for R. limosa Ng, 1987 . Typhlocarcinodes Alcock, 1900 , assigned with reservation to Chasmocarcinidae by Ng, Guinot & Davie (2008: 76), should clearly show a “supplementary plate” to remain included in the family. Microtopsis takedai Komai, Ng & Yamada, 2012 , recently assigned to Chasmocarcinidae , shows a penis “lying in a channel between sternites 7 and 8, completely covered by supplementary sternal plate between sternites 7 and 8, plate reaching halfway across exposed part of thoracic sternum” (Komai et al. 2012: 141, 151, fig. 2E, F).

The Chasmocarcinidae is treated here as a family whose members share two putative synapomorphies: (1) male sternite 8 deeply invaginated, forming a channel for the protection of the penis, thus giving the impression that the sternite is divided in two; (2) the carapace-thoracic sternum interlocking mechanism formed by thoracic sternite 8 and thoracic pleurite 8. The carapace is interlocked in a large, deep, transversal gutter between sternite 8 and pleurite 8, which is posteriorly raised ( Fig. 24C ). Large vulvae are characteristic of the family, as well in the cavernicolous Trogloplax and the freshwater Australocarcinus Davie, 1988 (with direct development) as well as in the marine species of Chasmocarcinus and the monotypic Camatopsis (see Female sternal gonopores, or vulvae above). The sperm of the freshwater Australocarcinus riparius ( Jamieson & Guinot 1996: 289) showed no clear affinity with those of any other Heterotremata, although confirming its heterotreme affiliation.

The Chasmocarcinidae , included in Goneplacoidea ( Ng, Guinot & Davie 2008: 75, 76; De Grave et al. 2009: 32; Schweitzer et al. 2010: 133; Castro et al. 2010: table 1), currently comprises three subfamilies: Chasmocarcininae ( Camatopsis , Chasmocarcinops Alcock, 1900 , Chasmocarcinus , Hephthopelta Alcock, 1899 , and some fossil genera such as † Falconoplax Van Straelen, 1933 , and † Collinsius Karasawa, 1993 ); Megaesthesiinae Števčić, 2005 ( Megaesthesius Rathbun, 1909 ) as previously suggested by Serène (1964b: 186; see also Crosnier 1975); and Trogloplacinae Guinot, 1986 ( Trogloplax , Australocarcinus Davie, 1988 ). The suprafamilial rank Chasmocarcinoidea Serène, 1964, proposed by Števčić (2005: 106), is not retained here, as in Castro et al. (2010), despite the two apomorphies mentioned above.

Acidops , Parapilumnus , Scalopidia Stimpson, 1858 , and Speocarcinus , previously included in or regarded as close to Chasmocarcinidae ( Serène 1964b; Davie & Guinot 1996; Karasawa & Kato 2003a, 2003b; Ng 2002), do not show the putative synapomorphies recognised herein for Chasmocarcinidae (see Superfamily Goneplacoidea : Family Acidopsidae , Family Scalopidiidae ; Superfamily Xanthoidea : Family Pseudorhombilidae , Subfamily Speocarcininae ).

A penial groove resembling the chasmocarcinid channel has been observed in some fossil species of Chasmocarcinu s, in † Collinsius Karasawa, 1993 , and † Falconoplax Van Straelen, 1933 ( Tavares 1992a; Blow & Bailey 1992; Schweitzer & Feldmann 2001a). The inclusion of extinct genera in Chasmocarcinidae was based on a set of characters of the carapace, abdomen, cephalic and thoracic appendages ( Feldmann & Zinsmeister 1984; Schweitzer & Feldmann 2001a; Karasawa 1997; Karasawa & Fudouji 2000; Collins in Collins et al. 2003; Karasawa & Kato 2003a, b; Schweitzer & Karasawa 2004).

† Falconoplax was previously considered a goneplacid ( Van Straelen 1933: 11; Feldmann & Schweitzer 2004: 16), a tymoline ( Glaessner 1969: R492), or a dorippid derived from † Sodakus ( Vega et al. 1995: 246) . Bailey & Blow (1987: 74) and Blow & Bailey (1992: 175) even synonymised † Falconoplax with Chasmocarcinus within the Goneplacidae , a synonymy not accepted by Schweitzer & Feldmann (2001a: 339), who reinstated † Falconoplax . The peculiar configuration of the penial region at the sternite 8 level, commented by Glaessner & Secretan (1987), led Tavares (1992a) to transfer † Falconoplax from Cyclodorippidae to Chasmocarcinidae . Inclusion of † Falconoplax in Chasmocarcinidae was followed by all subsequent authors ( Schweitzer & Feldmann 2001a: 338; Karasawa & Kato 2003a: 151; 2003b: 143, table 8; Schweitzer et al. 2004: 103; Feldmann & Schweitzer 2004: 16, fig. 3A; De Grave et al. 2009: 32; Schweitzer et al. 2010: 133). Indeed, the type species † Falconoplax kugleri Van Straelen, 1933 ( Van Straelen 1933: 11, fig. 6), represented by a great number of type series specimens from the Upper Eocene of Venezuela including some males with a complete ventral surface, shows a “supplementary plate”. In contrast to the closed groove of the other chasmocarcinids, the penial groove is wide, opened in † F. kugleri ( Glaessner & Secretan 1987: 11, pl. 2, figs. 13c; Tavares 1992a: figs. 1A, 2C, D), supposedly leaving the penis largely exposed. Our examination of a male paratype of † F. kugleri (MNHN.F.R53027), with an exceptionally well-preserved sternite 8 confirms this special condition, perhaps explained by the fact that the specimen is an internal mould. A similar pattern has been figured by Blow & Bailey (1992: pl. 1, fig. 7, as † Chasmocarcinus kugleri ) in the internal mould of another male paratype deposited in the Naturhistorisches Museum, Basel. Schweitzer & Feldmann (2001a: 339) hypothesised, however, that † Falconoplax could be an ancestral state of the chasmocarcinid organisation, with an incompletely invaginated sternite 8 for penis protection. The presence of supplemental plate could not be observed in four specimens from the Lower Miocene of Venezuela only represented by dorsal carapaces that were assigned to † F. kugleri by Feldmann & Schweitzer (2004: 16). The fossil record of † F. kugleri in Venezuela is quoted by Aguilera et al. (2010: 112). The thoracic sternum of † F. bicarinella Collins & Morris, 1976 ( Collins & Morris 1976: pl. 18, fig. 7), from the Eocene of Barbados, only represented by carapaces, is unknown.

† Bicarinocarcinus collinsi Glaessner & Secretan, 1987 (p. 6, pl. 1, figs. 2–4), from the Eocene of Pakistan (Sulaiman Range), is known by an entire carapace, a fragment of carapace, and the cephalothorax of a male with a well-preserved thoracic sternum, all deposited in the MNHN. Unfortunately, the sternum is sharply broken just at the limit between the sternites 7 and 8, so the presence of a penial groove is questionable.

† Collinsius simplex Karasawa, 1993 ( Karasawa 1993: 73, pl. 21, fig. 8; 1997: 61, pl. 23, figs. 8, 10; Karasawa & Kato 2003a: 151; 2003b: 143), from the Oligocene, shows a “supplementary plate” with a closed channel as in Chasmocarcinus , which justifies its placement in Chasmocarcinidae . It is noteworthy that these fossils already display a coxo-sternal condition. A similar condition, with a “supplementary plate”, should be present in other fossil chasmocarcinids.

† Chasmocarcinu s robertsi Blow & Bailey, 1992 , shows sternite 8 of in males with “a broad, shallow transverse depression”, interpreted as “genital groove and covering plate”, thus closed ( Blow & Bailey 1992: 178, pl. 1, fig. 5, pl. 2, fig. 7), which resembles a double plate. The vulva of the female is circular and large ( Blow & Bailey 1992: 172, pl. 2, fig. 5), extending across most of sternite 6 as in living members of Chasmocarcinus (see Female sternal gonopores, or vulvae; Castro et al. 2010: table 1).

Family Conleyidae . The male gonopore is coxal in the monotypic Conleyidae . The penis, moderately long and partially protected by laterally expanded episternite 7, shows a trend to a coxo-sternal condition ( Ng & Manuel-Santos 2007: 44, fig. 13F; see also P.K.L. Ng & N.K. Ng 2003; De Grave et al. 2009: 33; Castro et al. 2010: table 1).

Family Euryplacidae . The male gonopore is coxal. The penis shows a clear coxo-sternal disposition. The often long and proximally thick penis exits through a large gonopore that opens immediately above the P5 coxosternal condyle. The exposed portion of the penis is protected in various degrees by a concavity along the outer posterior margin of sternite 7. Episternite 7 variably extends sometimes to just above the gonopore, leaving the penis exposed and free when the coxa rotates during P5 movement. The penis is variously exposed in all genera: Eucrate (Guinot 1969b: fig. 35; Hsueh & Huang 2002: figs. 16E, 17D; Castro & Ng 2010a: fig. 11E), Frevillea A. Milne-Edwards, 1880 ( Castro & Ng 2010a: 51), Henicoplax Castro & Ng, 2010 ( Castro & Ng 2010a: fig. 25E), Heteroplax Stimpson, 1858 ( Castro & Ng 2010a: 71), Machaerus Leach, 1818 (Guinot 1969b: figs. 36, 38 as “ Pilumnoplax ”; Castro & Ng 2010a: figs. 30F, 32C), Nancyplax Lemaitre, García-Gómez, von Sternberg & Campos, 2001 ( Castro & Ng 2010a: fig. 31F), Platyozius Borradaile, 1902 ( Castro & Ng 2010a: fig. 35F), Psopheticoides Sakai, 1969 ( Castro & Ng 2010a: 89), Systroplax Castro & Ng, 2010 ( Castro & Ng 2010a: 91), Trissoplax Castro & Ng, 2010 ( Castro & Ng 2010a: fig. 41F), Trizocarcinus Rathbun, 1914 (Guinot 1969b: fig. 37; Ng & Castro 2007: fig. 3B; Castro & Ng 2010a: fig. 44F), Villoplax Castro & Ng, 2010 ( Castro & Ng 2010a: 112), and X enocrate Ng & Castro, 2007 ( Ng & Castro 2007: fig. 3B). The penis is protected and mostly concealed by the overlapping of episternite 7 with sternite 8 in Euryplax (Guinot 1969b: fig. 39; Castro et al. 2010: fig. 9C, D, table 1; Castro & Ng 2010a: figs. 16E, 17G). The region immediately around the penis in euryplacids is covered by a conspicuously elongated abdominal somite 3 that fits around episternite 7. Thoracic sternite 8 is thus completely covered ( Castro & Ng 2010a: fig. 6F) but a small portion remains visible in some species belonging to six genera (Castro et al. 2010: fig. 9B; Castro & Ng 2010a: figs. 16F, 30G, 44G, table 1).

The final emergence of the penis in Euryplacidae , as in Euryplax nitida and E. polita , is somewhat displaced onto the sternum, and its description can be difficult as when the coxo-sternal condition needs to be explained. Davie (2002: 198), for example, described the euryplacid condition as “clearly sternal with penis free but lying in more or less well-developed groove; becoming sternal with penis sheathed and/or protected proximally by a covered groove; or sternal, with penis lying in closed canal”. Stimpson (1859: 60), in his description of Euryplax nitida , correctly described the “verges of the male arising from the coxae of the posterior feet […] to the abdominal appendages through canals in the sternum”. The location of the male gonopore was not mentioned in Karasawa & Kato’s (2003b: 137) diagnosis of Euryplacinae Stimpson, 1871 , but it is given as coxal for Goneplacidae , which included Euryplacinae . Karasawa & Schweitzer (2006: 28) did not specify the condition, but Eucrate and Heteroplax are listed as lacking a penial groove. Števčić (2005: 71) stated that in euryplacids the “sexual openings [are] usually coxal to sometimes coxo-sternal”. The coxo-sternal condition of Euryplax as well as of the remaining Euryplacidae was clearly demonstrated by Castro et al. (2010: fig. 9C, D) and Castro & Ng (2010a: figs. 16E, 17G).

The Euryplacidae , traditionally placed as a subfamily of Goneplacidae sensu lato, is now considered to be an independent family within Goneplacoidea ( Karasawa & Schweitzer 2006: 57; Castro 2007: 613, 617; Ng & Castro 2007: 43; Ng, Guinot & Davie 2008: 78; De Grave et al. 2009: 33; Schweitzer et al. 2010: 133; Castro et al. 2010: table 1; Castro & Ng 2010a: 5), instead of constituting a separate superfamily ( Števčić 2005: 71).

Family Goneplacidae . The male gonopore is coxal, with a varying trend towards a coxo-sternal disposition. The Goneplacidae was revised by Castro (2007), who emended the diagnosis and restricted the family to 17 genera (see also De Grave et al. 2009: 33; Schweitzer et al. 2010: 134; Castro et al. 2010; Castro & Ng 2010b: 51).

The penis of Goneplacidae has been referred to as coxal to coxo-sternal ( Guinot 1969a, b, c; Števčić 2005: 63; Castro et al. 2010: table 1), coxo-sternal ( Castro 2007: 616; Ng & Manuel-Santos 2007: 45), coxal ( Karasawa & Kato 2003b: 137), and sternal or “sterno-coxal” ( Davie 2002: 190). Such different nomenclature shows the difficulty in interpreting and naming the transformation series observed among the Goneplacidae . Karasawa & Schweitzer (2006: 30) did not mention the position of the male gonopore in Goneplacidae , but referred to the absence of a penial groove in Carcinoplax .

The male gonopore opens immediately above the coxo-sternal condyle of the P5 coxa in Carcinoplax (see Guinot 1969a: figs. 61, 62, 65; 1989: figs. 2, 3; Ng & Manuel-Santos 2007: fig. 13D; Castro 2009: 952), Goneplacoides Castro, 2007 ( Komatsu & Takeda 2003: fig. 3a, as “ Goneplax ” marivenae ; Ng & Manuel-Santos 2007: fig. 7F, as Goneplax new species; fig. 13C, as “ Goneplax ” marivenae ), Goneplax Leach, 1814 ( Bouvier 1940: fig. 176; Guinot 1969a: figs. 63, 64, 67; Guinot & Castro 2007: fig. 3B), Ommatocarcinus White, 1852 ( Fig. 8G ), Paragoneplax Castro, 2007 , Psopheticus Wood-Mason, 1892 ( Guinot 1990: fig. 25), Pycnoplax (see Guinot 1969a: fig. 60, as Carcinoplax ; Castro 2012: 95, 99, 102), and Pedroplax Ng & Komai, 2011 ( Ng & Komai 2011: fig. 2E; see also Davie 2012a). The penis is soft, straight, and of moderate length. The gonopore and the proximal portion of the penis are protected by a variously expanded episternite 7 ( Guinot 1989: figs. 2, 3, Carcinoplax longimanus and C. monodi ; Hsueh & Huang 2002: fig. 10B, Carcinoplax purpurea Rathbun, 1914 ). The posterior margin of episternite 7 may completely cover the gonopore or it may cover at least only its anterior margin. The posterior portion or the entirety of the gonopore can be exposed when the coxa rotates with the movements of the P5. The relatively short, exposed distal portion of the penis is protected by the closed abdomen, its wide somite 3 typically reaching the episternite 7 and leaving varying portions of thoracic sternite 8 exposed, visible dorsally (e.g., Guinot 1989: figs. 2, 3; Guinot & Castro 2007: fig. 3B; Ng & Manuel-Santos 2007: fig. 10C), sometimes fitting under episternite 7 (e.g., Castro 2007: figs. 4B, 6B). Another variation is that in at least the adult of some species (e.g., Goneplax clevai , Ommatocarcinus macgillivrayi ), the proximal portion of the penis is left exposed because it is not covered by the closed abdomen.

The coxo-sternal disposition is more evident with the development of a groove that provides additional protection to a longer penis. In Hadroplax sinuatifrons the proximal portion of the penis, after exiting from the gonopore, is enclosed in a partially opened groove formed by a keel-like thickening on the anterior margin of thoracic sternite 8, and overhung by a relatively short episternite 7. The penis is also sheltered in a groove in Notonyx kumi Naruse & Maenosono, 2009 ( Naruse & Maenosono 2009: 184), as well as in N. nitidus . In Singhaplax wolffi , the penis is fully protected by running below suture 7/8, which essentially functions as a long, closed groove. In Microgoneplax Castro, 2007 , and Singhaplax dichotoma , S. platypoda , S. rhamphe , and S. styrax , the gonopore region on the P5 coxa and the penis are protected by a wider episternite 7, which overhangs over sternite 8. In all species of Microgoneplax and Singhaplax , the abdomen does not extend close to the P5 coxae and therefore does not cover the gonopore region. The only exception is S. platypoda , where the particularly wide abdomen reaches the gonopore region ( Castro 2007: fig. 36A). The abdomen is very broad in S. danielae Takeda & Komatsu, 2010 , and M. guinotae Takeda & Komatsu, 2010 ( Takeda & Komatsu 2010: figs. 2B, 5B, respectively); the disposition of the penis is not known. A short junction of sternites 7 and 8 occurs in Pedroplax ( Ng & Komai 2011: figs. 2E, 3G; Davie 2012a: 110).

Neommatocarcinus huttoni markedly departs from the typical pattern of Goneplacidae in having a penis with a sclerotised proximal portion and located in a groove ( Takeda & Miyake 1969: fig. 6a, b), which is unique for the Goneplacidae . This is one of the characters diagnostic of the Neommatocarcinidae Števčić, 2011 ( Števčić 2011) .

The assignment of Bathyplax typhla to Goneplacoidea is questionable (see Castro 2007: 619): Xanthidae ( Manning & Holthuis 1989; Tavares 1996b); monotypic Bathyplacinae Števčić, 2005, in Geryonidae within Goneplacoidea ( Števčić 2005: 66) ; and Bathyplacinae in Goneplacidae ( Ng, Guinot & Davie 2008: 80) . The wide and rather long penis, which emerges from the large coxal gonopore, is situated immediately above the P5 coxosternal condyle. A small proximal portion of the soft penis lies in a short groove and remains exposed, but its remaining portion is protected by the closed abdomen, wide somite 3 of which reaching the episternite 7. Sternite 7 extends onto the P5 coxa but it is not in contact with sternite 8, a large portion of which is exposed dorsally as an oblique plate (Guinot 1969c: fig. 96; Tavares 1996b: fig. 1E, F).

Family Litocheiridae . Litocheira bispinosa , the type species and perhaps the only species of the genus ( Ng, Guinot & Davie 2008: 83; see also Tesch 1918b; Gordon 1931; Guinot 1969a, b, 1971a), shows a coxal gonopore, just above the coxo-sternal condyle, partially surrounded by expanded episternite 7 and an outer prolongation of sternite 8. The penis is basally thick and continues as a long, soft tube, which lies in a concavity posterior to suture 7/8, and is covered by large abdominal somite 3 ( Fig. 25G ).

The location of the male gonopore was a source of confusion, being considered either sternal ( Balss 1933: 44) or coxal ( Türkay 1975b: fig. 27). Litocheira was misinterpreted as a primitive catometope (sternal gonopore) by Türkay (1983a: 101, 102), perhaps because of the existence of the penial groove. The genus was traditionally assigned to Goneplacidae ( Tesch 1918b: 163; Balss 1933: 43; 1956: 1656), and restricted to its type species without familial assignment, the remaining species being transferred to the Pilumnidae (Guinot 1969c: 697; 1971a: 1078). Litocheira , with one related genus, Georgeoplax Türkay, 1983 , was once again included in Goneplacidae ( Türkay 1975b: 124) as a basal representative but later assigned to Chasmocarcininae ( Davie 2002: 196) . It is the onomatophore (type genus) of a separate family, Litocheiridae Kinahan, 1856 , raised to Litocheiroidea by Števčić (2005: 61) (see Low et al. 2012c for correct authority). Ng, Guinot & Davie (2008: 83, fig. 71) provisionally placed the taxon as a family within Goneplacoidea , and Castro et al. (2010: fig. 9E, table 1) recognised its goneplacoid status (see also De Grave et al. 2009: 33; Schweitzer et al. 2010: 136).

Litocheira clearly does not share any of the synapomorphies of Chasmocarcinidae and therefore should not be included in this family. Despite their grapsoid facies, Litocheira and Georgeoplax are neither grapsids nor plagusiids, and do not belong to a thoracotreme family (sternal male gonopores). The coxal gonopores of Litocheira are evidence of a heterotreme condition. In contrast to Goneplacidae , the Litocheiridae has male abdominal somites 1, 2 dorsally placed, somites 1–3 of the same width, a heart-shaped telson ( Fig. 25E ), a stout, twisted, setiferous G1 (observed as “grapsoid” by Türkay 1975b), both G1 and G2 with long protopodites, a simple, long, and straight G2 ( Fig. 25A–D ), a narrow and longitudinally expanded thoracic sternite 7 ( Fig. 25G ), and an arched and wide front.

Additonal features of Litocheiridae include a broad male abdomen ( Fig. 25E ), with all somites free (instead of somites 3–5 fused according to Davie 2002: 196); flexion of the male abdomen in the middle of somite 3; abdominal somite 6 with deep sockets for the abdominal-locking mechanism; thoracic sternite 8 with a very small portion visible dorsally, instead of completely concealed according to Števčić (2005: 61); thoracic sternal suture 3/4 conspicuous, deep; sutures 4/5 and 5/6 interrupted; suture 6/7 complete; suture 7/8 interrupted (Castro et al. 2010: fig. 9E), instead of complete according to Števčić (2005: 61); median line along sternites 7 and 8; large vulva with two sclerotised prominences and closed by a membrane ( Fig. 25F ; Castro et al. 2010: fig. 9E); G2 long, and straight, consisting of a simple flagellum ( Fig. 25D ), in contrast to the short and sigmoid pilumnoid G2 characteristic of a number of species previously attributed to Litocheira as in Tesch (1918b; see Guinot 1969c).

Family Mathildellidae . The male gonopore is coxal. The wide penis, which exits from a large gonopore situated on the coxa (and not on the condyle, see Condylar protection), ends in a narrow papilla, lies in a very shallow, hardly visible depression on sternite 8, and is only protected by the transversely broad abdominal somite 3; episternite 7 is not expanded ( Guinot & Richer de Forges 1981a: figs. 4, 5C, E; Ng & Manuel-Santos 2007: fig. 13E; Castro et al. 2010: table 1).

The Mathildellidae , considered to be a portunoid family by Karasawa & Schweitzer (2006: 41, 61) and Karasawa, Schweitzer & Feldmann (2008: 94, 96), was recognised as a goneplacoid family by Takeda & Watabe (2004), Ng & Manuel-Santos (2007), Castro (2007), Ng, Guinot & Davie (2008), De Grave et al. (2009: 33), Schweitzer et al. (2010: 136), and Castro et al. (2010).

Family Progeryonidae . The male gonopore is coxal, being large and opening just anterior to coxo-sternal condyle of P5 coxa. The penis, which is moderately long, originates “directly from base of coxa of P5” ( Castro & Ng 2008: 54) as in Progeryon vaubani and P. mararae ( Guinot & Richer de Forges 1981a: fig. 3A, D), P. mus ( Castro & Ng 2008: fig. 7G), and Rhadinoplax microphthlamus ( Castro & Ng 2008: figs. 3, 4G). Episternite 7 is moderately expanded but does not cover the penis (see Castro et al. 2010: table 1). In the monotypic Paragalene Kossmann 1878 , the penis protrudes from the coxal gonopore and shows as a broad, soft proximal expansion with a short distal extension ( Ng, Guinot & Davie 2008: 84; Castro & Ng 2008: 63, 67, fig. 7H).

The Progeryonidae was included in Goneplacoidea by Ng & Manuel-Santos (2007: table 1), Ng, Guinot & Davie (2008: 84), Castro & Ng (2008: 54), and De Grave et al. (2009: 33).

Family Scalopidiidae . The male gonopore is coxal, the condition coxo-sternal in Scalopidia spinosipes , the only species in the family. The long penis, which runs along suture 7/8, is protected in a narrow channel formed by the incomplete juxtaposition of sternites 7 (expansion of episternite 7) and 8, and its unprotected dorsal portion is slightly sclerotised (Castro et al. 2010: fig. 9F). This is clearly a derived coxo-sternal condition. The channel between the incompletely juxtaposed sternites 7 and 8 in Scalopidia is not homologous to the chasmocarcinid “supplementary plate” resulting from a deep invagination of sternite 8.

Scalopidia was included in Goneplacidae by Huang (1994: 592) and in the goneplacid subfamily Chasmocarcininae by Ng et al. (2001: 34) and Hsueh & Huang (2002: 113). It is clear that Scalopidia , which is not a chasmocarcinid, deserves its own family. We disagree with Števčić (2005: 107) in excluding the Scalopidiidae from the Chasmocarcinoidea, and we refer it with more confidence to the Goneplacoidea (see Ng, Guinot & Davie 2008: 85; De Grave et al. 2009: 33; Castro et al. 2010: fig. 9F, table 1; Komai et al. 2012: 141).

Family Sotoplacidae . The male gonopore is coxal with an exit displaced in a sternal position in Sotoplax robertsi , the only species in the family. The long penis is protected by a closed canal formed by the joining of thoracic episternite 7 and sternite 8 ( Guinot 1984a: 92, figs. 2A, 3B; Almeida et al. 2008: fig. 2C; Castro et al. 2010: figs. 4, 5A, table 1; “p” in fig. 4, erroneously indicated as the penis, is actually the coxo-sternal condyle that covers it, the penis not being externally visible). Abdominal somite 3 is not conspicuously wider than other abdominal somites, therefore a very large portion of thoracic sternite 8 is visible dorsally. A derived coxo-sternal condition is evident. Sotoplax Guinot, 1984 , which is known from the male holotype of S. robertsi and new material from Brazil ( Almeida et al. 2008) and the Gulf of Mexico (Thoma et al. 2009), and tentatively included in Euryplacidae ( Ng, Guinot & Davie 2008: 78, 79), was recently elevated to the family rank (Castro et al. 2010).

Family Vultocinidae . The male gonopore is coxal. The short penis is only partially protected by a conspicuously elongated episternite 7 and the transversely wide abdominal somite 3 ( Ng & Manuel-Santos 2007: fig. 13A, B; Ng & Richer de Forges 2009: fig. 2A; Castro et al. 2010: table 1). A trend towards a coxo-sternal condition is observed in this monotypic family. The Vultocinidae , despite a somewhat pilumnoid appearance, is clearly a goneplacoid family ( De Grave et al. 2009: 33).

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 24. Coxo-sternal condition in Chasmocarcinidae. A, B, Trogloplax joliveti Guinot, 1986 (Trogloplacinae), male 20.0 × 27.0 mm, paratype, Papua New Guinea, New Britain (MNHN-B12794). A, thoracic sternum (abdomen removed); B, details of sternites 7 and 8, portion of penis (dotted line) enclosed in the “double plate”. C, Chasmocarcinus typicus Rathbun, 1898 (Chasmocarcininae), male 9.0 × 12.0 mm, Brazil (MNHN-B29900): penis (proximal portion dorsally visible) enclosed in invagination of sternite 8 after perforating P5 coxa, and emerging as papilla (left); P5 coxa removed to expose ejaculatory duct (right). c, coxo-sternal condyle; cx4, cx5, P4, P5 coxae; e.d., ejaculatory duct; e.p., exposed part of penis; g.i., gutter for carapace-thoracic sternum interlocking mechanism; l, invagination line of sternite 8; m.l., median line; p, penis; pa, papilla; p.p., proximal portion of penis; s.c., sterno-abdominal cavity; 4–8, sternites 4–8; 4/5–7/8, thoracic sternal sutures 4/5–7/8. Scale bar: 5 mm (C).

FIGURE 25. Litocheira bispinosa Kinahan, 1856 (Litocheiridae), male 8.2 × 10.0 mm, female 8.5 × 11.0 mm, Australia, Tasmania (MNHN-B17754). A–C, G1, two different views and apex; D, G2; E, male abdomen; F, female thoracic sternum, with large vulvae; G, penis lying in depression posterior to suture 7/8; notice expanded episternite 7. cx5, P5 coxa; p, penis; v, vulva. 4–8, thoracic sternites 4–8; 4/5–7/8, thoracic sternal sutures 4/5–7/8. Scale bars: 2 mm (A–C, G); 1 mm (D); 3 mm (E); 5 mm (F).