Inachoididae, , Hymenosomatoidea, and Dorippoidea, 1851

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 : 226-232

Affinities between Inachoididae and Inachidae

One of the main characteristics of the Inachoididae is the latero-external exposure of the posterior pleurites ( Drach & Guinot 1982, 1983) so that the arthrodial cavities of pereopods become placed on the same plane as the carapace, leading to the suppression of the branchiostegite, as in Dorippoidea . This feature that could be regarded as exclusive to Inachoididae is also found in Inachidae . Some pleurites are exposed in Inachidae but to a lesser extent as in Inachoididae , and, moreover, remain detached from the carapace edge, which rests on a shallow groove at the surface of only pleurites 7 and 8 without constituting a “setting gutter” as in Inachoididae . In Inachus sclerite 8 continues as a narrow plate by partially encircling the P5 arthrodial cavity just to its articulation by the coxo-sternal condyle on sternite 8. The exposed pleural sclerites, which are always narrow and vary in shape and size from sternites 6 to 8 ( I. angolensis ) to only sternites 7 and 8 ( I. phalangium ), and the first abdominal somite do not seem to be part of the carapace in Inachidae . A similar disposition occurs in Achaeus . Capartiella also shows this typical inachid groudplan ( Fig. 49A ) with, however, some peculiar characters (see below).

In Cyrtomaia Miers, 1885 (type species: Cyrtomaia murrayi Miers, 1886 , subsequent designation by Guinot & Richer de Forges 1982), pleurites 5–7 extend somewhat beyond the carapace as triangular sclerites at the P2–P4 coxae levels; pleurite 5 only extends as a single, pointed sclerite posterior to the P2 coxa. The pointed portions of the exposed pleural sclerites 5 and 6 on each side of the corresponding coxae (P2, P3) result from the markedly concave margins of the calcified distal parts of these pleurites, of which only the extremity of each side extends beyond the carapace edge. Only the posterior portion of pleurite 5 is exposed, thus only one sclerite is visible at the P2 level. Pleurite 8 is only exposed by the small sclerite bearing the P5 coxo-pleural condyle, which fits into a deep gynglyme; the sclerite that partially encircles the P5 arthrodial cavity is narrower than in Inachus . Only a faint gutter receives the carapace edge in Cyrtomaia .

The Inachidae , at least Inachus (represented by its type species I. phalangium and its strictly closely allied genera), thus differs from Inachoididae ( Fig. 47G ) by having a variable number of pleurites with exposed lateroexternal parts that are free and only form small sclerites, instead of more developed plates appearing as “fused” to the carapace; the first abdominal somite also does not form a part of the carapace in Inachidae . The thoracic sternum is considerably widened in both Inachoididae and Inachidae . Sutures 4/5–7/8 are, however, more laterally confined in Inachidae (exemplified here by Inachus ) ( Fig. 50A, B ), where the press-button lies in the unfused median part of the sternal plate. Additionally, and in contrast to Inachoididae , the inachid thoracic sternum is not connected to the carapace between P1 and P2 nor connected to the exposed pleurites 5–8 between the posterior pereopods, sternal extensions being absent in the Inachidae (at least in the examined genera). The sternal pattern of Inachidae (studied here in Inachus ) is peculiar because the median line is not evident at first glance, but it is, however, recognisable in males as a thin sulcus at the sternites 5–7 level, and prolonged by a flat median strip at the sternite 8 level. A raised median plate is accordingly present along sternites 5–7 that are prolonged by a thickened portion on sternite 8. The median line and median plate are absent in inachid females ( Fig. 47C ). The pattern of median line and median plate differs in Inachoididae , which presents at least two distinct patterns in males, with a median line along sternites 6–8 (e.g., Anasimus ) or with a thick bridge at the level of sternite 8 (e.g., Leurocyclus ) ( Guinot 2012).

It is surprising to notice that the exposure of the posterior pleurites, which has been overlooked by most carcinologists, is present in a large number of American inachid genera, for example in Podochela Stimpson, 1860 (type species by subsequent designation by Miers, 1879: Podochela grossipes Stimpson, 1860 ), Coryrhynchus Kingsley, 1879 (type species by subsequent designation by Miers, 1879: Podonema riisei Stimpson, 1860 ), and Ericerodes Rathbun, 1897 (type species by monotypy: Ericerus latimanus Rathbun, 1894 ) ( Ng, Guinot & Davie 2008 updated). In his revision of Podochela , restricted to only some species, the other taxa being assigned to the above-mentioned genera, Coelho (2006), no more that previous authors such as A. Milne-Edwards (1873–1880), Rathbun (1925), Garth (1958), seems to have not observed the character that is yet obviously visible. The expansion of the posterior pleurites beyond the carapace’s margin is particularly notable and easily discernable in several species figured by A. Milne-Edwards (1873–1880), such as P. macrodera Stimpson, 1860 (A. Milne- Edwards 1873 –1880: pl. 34, fig. 3), Coryrhynchus riisei (A. Milne-Edwards 1873–1880: pl. 34, fig. 1, as Podochela Reisei ), and Ericerodes gracilipes ( Stimpson, 1871) (A. Milne-Edwards 1873–1880: pl. 35, fig. 1, as Podochela gracilipes ).

The nomen Podochelinae Neumann, 1878 ( Neumann 1878) has been rehabilitated ( Guinot 2012) to accommodate the above-mentioned American inachid genera characterised by a narrow carapace; a wide thoracic sternum (Coehlo 2006: figs. 7, 10, 14), sometimes in the form of raised plates that are separated by deep depressions (A. Milne-Edwards 1873–1880: pl. 34, fig. 1a, pl. 36, fig. 3d); a quadrate first abdominal somite ( Hendrickx 1987: fig. 1A, B; Coehlo 2006: figs. 8, 11, 12, 15, 16, 19); P1 insertion points close to each other (Coehlo 2006: figs. 7, 10, 14); and a narrow junction of the thoracic sternum with the pterygostome. Podochelines, called “neck crabs” or “frilly-neck crabs”, have small bodies and long legs, recurved setae on the rostrum, carapace and legs that are used for decoration ( Wicksten 2008). The inclusion in Podochelinae of Metoporhaphis Stimpson, 1860 (type species by monotypy: Leptopodia calcarata Say, 1818 ) and Erileptus Rathbun, 1893 (type species by monotypy: E. spinosus Rathbun, 1893 ) requires confirmation. Ericerodes hemphilii (Lockington, 1877) and Erileptus spinosus Rathbun, 1893 (Wicskten 2012: fig. 49G, H) show clearly exposed pleurites, as well as Podochela lobifrons Rathbun, 1893 (Wicskten 2012: fig. 50A). Metoporhaphis calcarata (Say, 1818) , known as the “false arrow crab”, shows a particular defensive behaviour referred to as “stockade” ( Wicksten 2011: fig. 50A) (see below).

Other small-size American inachids, e.g., Anomalopus Stimpson, 1871 (type species by monotypy: Anomalopus furcillatus Stimpson, 1871 ) and Eucinetops Stimpson, 1860 (type species by monotypy: Eucinetops lucasii Stimpson, 1860 ), which show a narrow, hardly visible exposure of pleurites, must be grouped in another subfamily, Anomalopodinae Stimpson, 1871 ( Stimpson 1871: 124) (a replacement nomen for Anomalopinae), a nomen not used by Rathbun (1925) and Garth (1958) but resurrected by Coelho (1999a: 58; 1999b: 153, 156), and recognised as an inachine tribe, Anomalopini [sic] Stimpson, 1871, by Števčić (2005: 95) (see Guinot 2012).

The absence in Inachidae ( Fig. 47C ) of the vertical pillars that connect the axial skeleton with the internal surface of the carapace in Inachoididae (a case unequalled in Brachyura ) ( Fig. 47G–I ) is an indication of the less specialised organisation of inachids. The inachoidid skeleton is more dorsoventrally flattened than that of Inachidae . Nevertheless, the groundplan, with a regularly compartmented axial skeleton, is plesiomorphically similar in Inachidae and Inachoididae . An examination of all inachid genera should demonstrate the reliability of the character state exposure of the pleurites.

The other characters shared by Inachidae and Inachoididae are numerous, and the affinities between the two families are not called into question here. The male abdomen consists of five free somites plus the pleotelson in Inachidae ( Figs. 49C, D , 50A ) as well as in Inachoididae ( Fig. 50C, D ). An anterior displacement of the vulva on the fused median part of the broad thoracic sternum is frequently observed in both families ( Fig. 48A, B ), sternite 6 being anteriorly projected so that the vulvar opening may be located anterior to suture 4/5.

In a re-evaluation of larval support for the monophyly of majoid families, Marques & Pohle (2003: 76, 77, fig. 2) found that the Inachidae + Inachoididae group ( Macrocheira excepted) formed a monophyletic clade in unconstrained analyses, with Leurocyclus nested as the “most basal” taxon, and that Inachidae ( Inachus , Achaeus , Macropodia ) was a highly derived group; no larval characters indicated, however, that Leurocyclus shared a common ancestor with other Inachoididae . According to Santana & Marques (2009: 55) all inachoidids with a completely described larval development [ Anasimus latus ( Sandifer & Van Engel 1972) , Pyromaia tuberculata (see Webber & Wear 1981; Terada 1983; Fransozo & Negreiros-Fransozo 1997; Luppi & Spivak 2003), Paradasygyius depressus Bell, 1835 ( Bell 1835: 88) (see Pohle & Marques 2000)] conform for the most part to the general pattern of Majoidea (two zoeal stages), although Leurocyclus differs from other inachoidids by several features and from all majoids by the setal formula of the distal article of the mxp2 endopodite in both zoeal stages. Discontinuities in the morphometric relationships in growth rates of carapace, abdomen and chelipeds have been detected in populations from Patagonia of the “knobbed spider crab” Leurocyclus tuberculosus ( Barón et al. 2009) . Changes have nevertheles been also observed in the size of pereopods 2 and 3 at morphological maturity (Guinot 1984), hence the existence of two morphotypes: small-sized individuals with narrow pereopods (morph referrable to L. gracilipes (A. Milne-Edwards & Bouvier, 1923)) and adults with stout pereopods (morph corresponding to L. tuberculosus ) (see Guinot 1984: figs. 3A–C, 4, pls. 1, 2). Despite a questionable geographic distribution (Guinot 1984; Boschi et al. 1992; Melo 1996; Spivak 1997; Braga et al. 2002; Vinuesa 2005; Boschi & Gavio 2005; Barón et al. 2009; Stauffer et al. 2011) and without information about the possible sympatry of the two morphotypes, a single species, L. tuberculosus , is currently recognised in Leurocyclus . Discontinuities relative to overall body size, proportion of the carapace, and relative stoutness of the pereopods in the oregoniid Hyas coarctatus Leach, 1815 , may be related to a distinctive allometric growth pattern and/or to the existence of distinct subspecies ( Pohle 1991; Honma & Muraoka 1992; Komai & Yakovlev 2000).

The statement by Drach & Guinot (1983: 42) that Inachoididae is at a more derived stage than Inachidae (“ les Inachoididae présentent un niveau d’évolution plus avancé que les Inachidae ”) must be understood in a new perspective. The Inachoididae , despite the absence of an early fossil record, is probably more ancient than Inachidae . The degree of cohesion of the inachoidid skeleton, regularly compartmented and connected to the carapace by pillars, is indicative of a long evolutionary history that explains the highly specialised skeleton. Despite larval data not providing synapomorphies for Inachoididae , thus not supporting its separation from Inachidae ( Pohle & Marques 2000; Marques & Pohle 1998, 2003), Inachoididae is nevertheless recognised on the basis of the morphology of the adults (see above). In a molecular study on Majoidea where Inachidae and Inachoididae (apart from Stenorhynchus ) were not sequenced, Hultgren et al. (2009: 448, figs. 1, 2) concluded that these two families were “crucial to further resolve branching patterns at the base of the majoid tree”.

Guinot & Richer de Forges (1997: 489, fig. 15D, E, G) brought attention in this context to the West-African majoid Capartiella , monotypic with C. longipes ( Capart, 1951) ( Capart 1951: 62, fig. 19, pl. 1, fig. 1, pl. 2, figs. 21, 22, as? Achaeus ; Monod 1956: 537, fig. 746; Rossignol 1962: 122; Forest & Guinot 1966: 108, fig. 14; Crosnier 1967: 340; all as Physachaeus ? longipes ; Manning & Holthuis 1981: 277, fig. 69; Henriksen 2009: 55, fig. 23). Capartiella Manning & Holthuis, 1981 , is considered an inachid ( Manning & Holthuis 1981: 265, 277: Ng, Guinot & Davie 2008: 110). It shows a lateral exposure of pleurites 5–8 that are calcified like the carapace ( Fig. 49A ). The original drawing of C. longipes in Capart (1951: fig. 19) (with a clear exposure of several pleural sclerites) that was reproduced by Monod (1956) and Manning & Holthuis (1981) does not reflect the triangular shape of the carapace ( Fig. 49A ). These exposed pleural sclerites are detached from the carapace, which simply lies above them, instead of being “fused” with the lateral carapace edge as in the typical inachoidid condition; the first abdominal somite of Capartiella also does not seem to be part of the carapace, thus does not correspond to an inachoidid condition. Capartiella is particularly interesting because its pleotelson bears on each side a small, partially moveable flap having a ventral socket that fits into an acute sternal prominence: they represent a press-button system for abdominal locking ( Fig. 49B–D ). These traits, not previously singled out, were briefly discussed by Guinot & Richer de Forges (1997), who suspected a similarity with the intercalated platelets of the basal Hymenosomatoidea ( Fig. 29C–E ). One can now assume the homology of this flap ( Fig. 49C, D ) with a vestigial uropod, although its shape is not so typical as in Odiomarinae . Retention of such an ancestral structure in Capartiella attests its basal position in the Inachidae , which is one of the most basal majoid families. The retention of a true uropod in Hymenosomatoidea and of a moveable flap in Inachidae is probably inherited from a close common ancestor rather than indicative of convergence. The male and female abdomens of Captartiella consist of five somites plus pleotelson as in Inachidae , Inachoididae , and Odiomarinae . Other characters of Capartiella , including a triangular carapace ( Fig. 49A ), long eyestalks, absence of a sternum/pterygostome junction, and a sternum/pleurites junction, are shared with the other Inachidae . The G1 of C. longipes (see Forest & Guinot 1966: fig. 14) is, however, distinctive, being straight and with the lobed, inner distal part of each G1 close to each other.

The Indo-West Pacific Physachaeus Alcock, 1895 (type species: P. ctenurus Alcock, 1895 ; see Alcock & Anderson 1896: pl. 18, fig. 1; Doflein 1904: pl. 42; Griffin & Tranter 1986: fig. 8c), to which Capartiella longipes was initially referred to, appears not to show exposed lateral pleurites or moveable uropodal flaps. The status of Physachaeus needs to be re-examined.

The sockets of the press-button mechanism of most Inachidae externally show as salient, laterally expanded prominences, as in Oregoniidae (see below). They are not limited by sutures but may be indicative of the original uropods transformed into sockets ( Fig. 50A, B ), these being more dorsally marked than in Inachoididae ( Fig. 50C– F ) and Majidae ( Fig. 50G ).

The Inachidae is a basal family within the Majoidea . The simple, straight or weakly curved G1, with terminal or subterminal aperture ( Türkay 1976: figs. 33–35; Griffin & Tranter 1986: 3), and the unprotected eyestalks indicate a plesiomorphic state. The Upper Cretaceous (Cenomanian) record of the † Priscinachidae , a family close to Inachidae (see Breton 2009: 519, 521), demonstrates the early occurrence of spider crabs. Larval characters support the monophyly of the family, except at least for Macrocheira that was regarded as the “most basal” genus of all Majoidea (see Clark & Webber 1991; Marques & Pohle 1998, 2003).

Some remarks on Oregoniidae and other Majoidea are in order. The Oregoniidae shows a pleural pattern analogous to that of the Inachidae , but with notable differences. In Hyas coarctatus pleurites 6 and 7 extend beyond the carapace, the narrow exposed portions only showing as bluntly triangular sclerites between the pereopods. Pleurites 5–7 are exposed in Oregonia gracilis , the exposed portions forming sclerites larger than in H. coarctatus . In Chionoecetes the posteriorly expanded carapace covers the dorsal surface except for very small pleural portions, which are more visible in young individuals. As in Inachidae , the oregoniid genera are characterised by exposed sclerites and a first abdominal somite that do not appear “fused” to the carapace. In contrast to Inachidae , Inachoididae and Odiomarinae , the abdomen of Oregoniidae consists of 6 free somites plus the telson in both sexes (no pleotelson).

The Oregoniidae is generally considered the closest to the ancestral stock of extant Majoidea ( Rice 1980; Clark & Webber 1991; Marques & Pohle 1998; Ng, Guinot & Davie 2008; Hultgren & Stachowicz 2008b). Oregonia gracilis and O. bifurca Rathbun, 1902 , show on abdominal somite 6, at the location of the sockets, externally salient, elongated plates that are obviously homologous to uropods in the process of being incorporated into the abdomen ( Rathbun 1925: figs. 20, 21); such a pattern is not present in O. kurilensis (Kobjakova, 1962) (see Komai & Yakovlev 2000: fig. 4G). In Hyas coarctatus the socket practically extends along the whole length of abdominal somite 6, with a deep anterior part fitting a strong press-button. Such an elongated socket is unusual in Eubrachyura, where the socket generally occupies only a portion of the somite, as in the palicid socket ( Fig. 50H ) that is posteriorly located, a condition rarely found in eubrachyurans. Marked inflated portions of abdominal somite 6, corresponding to deep sockets, occur in Inachidae ( Fig. 50A, B ; see above).

Larval characters support the monophyly of Oregoniidae , Macrocheira being basal to this family ( Marques & Pohle 1998, 2003; see also Clark & Webber 1991). Macrocheira should be excluded from Inachidae .

It is beyond the scope of this research to study the pleural disposition in all Majoidea , the group of Brachyura with the most species ( Ng, Guinot & Davie 2008). Only a few observations are included here, which must be verified in related taxa in order to eventually establish synapomorphies. In Majidae Majinae, here exemplified by Maja , pleurites 6 and 7 slightly extend beyond the carapace by showing as triangular sclerites at the P3, P4 coxae levels; pleurite 5 only extends as a single triangular sclerite posterior to the P2 coxa; the small pleurite 8 is covered by the carapace, with only the P5 pleuro-coxal sternal exposed. As in Cyrtomaia (see above) the pointed shape of the exposed pleural sclerite on each side of the coxa depends on the markedly concave margins of the external part of the pleurite, of which only the angular extremity extends beyond the carapace edge. In Maja , however, the carapace does not lie inside a gutter, and pleurite 8 does not encircle the P5 arthrodial cavity. Maja is characterised by sternal extensions that connect sternites 4–7 to the corresponding pleurites 4–7, these extensions being very narrow and deeply recessed between the pereopods.

In the Pisidae Dana, 1851 , exemplified here by Pisa Leach, 1814 , small exposed pleural sclerites are visible at the P2–P4 coxae levels. As in Majinae, there are narrow and deep sterno-pleural extensions 4–7. In another pisid, Phalangipus Latreille, 1828 , there are minute, exposed pleural sclerites between the P2 and P3 and the P3 and P4 coxae, and a more clearly developed one between the P4 and P5 coxae. The extension that connects sternite 7 to pleurite 7 is obvious in Phalangipus , being on the surface at the same plane as sternite 7 instead of being recessed as in Pisa .

An extensive examination should yield homologies for providing valid and new diagnostic characters and for a better understanding of the groundplan of the brachyuran superfamilies and families. The interlocking of the carapace with the thorax, as well as the general architecture of the body, remains poorly known in Brachyura . A typically basal podotreme trait is a carapace with a markedly concave posterior border ( Fig. 51C, E, F ), but the interlocking of the carapace with the abdomen has not been properly studied in Eubrachyura.

Figures

FIGURE 29. Male gonopore (A, B) and dorsal platelets of the abdomen (C–E) in Hymenosomatidae. A, Cancrocaeca xenomorpha Ng, 1991, male 3.9 × 4.6 mm, paratype, Indonesia, Sulawesi (MNHN-B24450); B, Odiomaris pilosus (A. Milne- Edwards, 1873) (Odiomarinae), male 20.0 × 22.6 mm, New Caledonia (MNHN-B26146); C–E, same data as B: abdomen in dorsal and ventral views; notice on pleotelson (somite 6 fused to telson) the vestigial uropod as intercalated, dorsal platelet, with socket situated beneath, and uropod (D) with electron microscope (all after Guinot & Richer de Forges 1997: figs. 5B–D, 9A, B). a.c., sterno-abdominal cavity; cx5, P5 coxa; g, gonopore; G1, first gonopod; p, uropod as dorsal platelet; pt, pleotelson; s, socket; 6–8, thoracic sternites 6–8; 6/7, 7/8, thoracic sternal sutures 6/7, 7/8. Scale bar: 100µm (E).

FIGURE 47. Skeletons of Dorippidae (A, B), Inachidae (C), Hymenosomatidae (D–F), and Inachoididae (G–I). A, B. Medorippe lanata (Linnaeus, 1767), Mediterranean Sea, dorsal view. A, male, after removal of carapace; B, female, after removal of pleurites; C, Inachus dorsettensis (Pennant, 1777), female, Mediterranean Sea (MNHN): sagittal section. D–F, Odiomaris pilosus (A. Milne-Edwards, 1873), New Caledonia (MNHN): D, dorsal view after partial removal of carapace; E, axial skeleton, dorsoventral view after removal of pleurites; F, axial skeleton, sagittal section. G, H, Paulita tuberculata (Lemos de Castro, 1949); G, male 23.0 × 23.0 mm, French Guiana (MNHN-B19511): exposed pleurites 5–8 visible after removal of carapace; H, female: axial skeleton, sagittal section. I, Leurocyclus tuberculosus (H. Milne Edwards & Lucas, 1842), Brazil (MNHN): sagittal section. a, abdomen with pleopods; a1, first abdominal somite; c, carapace; cx5, P5 coxa; e, endopleurite; e.p., exposed pleurite; e5–e8, exposed pleurites 5–8; g, setting gutter of carapace; h, hymenosomian rim; j, junction plate; m, median plate; p, pleurite; pi, pillar; pl, pleopod; s, sella turcica; st, thoracic sternum; t, endosternite; v, location of vulva; y, eye; 3/4–6/7, endosternites 3/4–6/7; 4–8, pleurites 4–8. C, F, H, I: skeletons prepared by S. Secretan.

FIGURE 48. Location of vulvae. A–C, anterior displacement: A, Anasimus latus Rathbun, 1894 (Inachoididae), female 18.4 × 14.0 mm, French Guiana (MNHN-B17807); B, Capartiella longipes (Capart, 1951) (Inachidae), ovig. female 9.4 × 8.1 mm, Nigeria (MNHN-B19602). C, Halicarcinus planatus (Fabricius, 1775) (Hymenosomatidae), female 14.0 × 19 mm, South Pacific, Campbell I. (MNHN-B25960) (schematic); D, Hiroia krempfi Fize & Serène, 1956 (Cryptochiridae), female, Palau: vulvae not widely separated and sternal suture 7/8 complete (schematic, modified from Kropp 1990: fig. 6c); E, Pseudohapalocarcinus ransoni (Fize & Serène, 1956) (Cryptochiridae), female, Guam: vulvae located apart on broad thoracic sternite 6 (schematic, modified from Kropp 1990: fig. 12c). j, sternum/pterygostome junction; m.l., median line; v, vulva; 3–8, thoracic sternites 3–8; 4/5–7/8, interrupted thoracic sternal sutures 4/5–7/8; w, sternal wall.

FIGURE 49. Capartiella longipes (Capart, 1951) (Inachidae), male 8.2 × 6.5 mm, Dahomey (= Benin) (MNHN-B19590). A, carapace, dorsal view: notice exposed pleurites 5–8; B, ventral view; C, thoracic sternum, abdomen lifted, G1 lowered; D, detail of pleotelson with moveable flap supposedly homologous to vestigial uropod. a1, a5, abdominal somites 1, 5; b, pressbutton; c, carapace edge; cx1, P1 coxa; e5–e8, exposed pleurites 5–8; f, flap; G1, first gonopod; pt, pleotelson (somite 6 fused to telson); r, roof formed by thoracic sternite 8; 3–8, thoracic sternites 3–8.

FIGURE 50. A–G. Thoracic sternum (A, C, E, G) and ventral surface of abdomen (B, D, F) of Inachidae (A, B), Inachoididae (C–F), and Majidae (G). A, B, Inachus dorsettensis (Pennant, 1777), male 20.0 × 18.0 mm, France, Saint Martin de Ré (MNHN-B17337); C, D, Collodes leptocheles Rathbun, 1894, male 17.5 × 13.2 mm, Gulf of Mexico (MNHN-B14055); E, F, Pyromaia tuberculata (Lockington, 1877), male 17.0 × 12.2 mm, Baja California (MNHN-B9290); G, Prismatopus harmandi (Bouvier, 1906), male 46.0 × 24.5 mm, holotype, vicinity of Tokyo (MNHN-B22330). H. Palicus caronii (Roux, 1828), male 6.0 × 7.0 mm, eastern Atlantic (MNHN-B16335): ventral surface of abdomen with long socket on somite 6. b, press-button.

FIGURE 51. Articulation of abdominal somites, dorsal view. A, Nephrops norvegicus (Linnaeus, 1758) (Nephropidae), eastern Atlantic (MNHN); B, †Eocarcinus praecursor Withers, 1932 (†Eocarcinidae), Lower Jurassic, England, paratype (BM 23091); C, Dicranodromia sp. (Homolodromiidae), Philippines (MNHN-B28939); D, Ranina ranina (Linnaeus, 1758) (Raninidae), Madagascar (MNHN-B7662); E, Homola ranunculus Guinot & Richer de Forges, 1995 (Homolidae), New Caledonia (MNHN- B19871); F, Sternodromia spinirostris Miers, 1881 (Dromiidae), male, Congo (R.O.C.) (MNHN-B7863); G, Medorippe lanata (Linnaeus, 1767) (Dorippidae), male, West Africa (MNHN). a1–a3, abdominal somites 1–3; cx5, P5 coxa; m, articular membrane; p, abdominal pleura; t1–t3, abdominal tergites 1–3 with calcified anterior (a) and membranous posterior (P) parts; t, telson.