Dynomenidae Ortmann, 1892

Guinot, Danièle, 2008, A re-evaluation of the Dynomenidae Ortmann, 1892 (Crustacea, Decapoda, Brachyura, Podotremata), with the recognition of four subfamilies, Zootaxa 1850, pp. 1-26 : 4-5

Family Dynomenidae Ortmann, 1892

Dynomenidae Ortmann, 1892: 541 ; Alcock 1900: 127, 133; 1901: 34; Rathbun 1937: 51; Glaessner 1960: 46, fig. 22; 1969: R487; 1980: 190, fig. 22; Wright & Wright 1950: 26, fig. 13; Wright & Collins 1972: 48; Jamieson et al. 1993: 311 –322, fig. 3; 1995: 274; Guinot 1978: 231; 1993a: 1226; 1995: 186; Guinot et al. 1994: fig. 7; 1998: 78, 92, 93, fig. 8; Guinot & Bouchard 1998: 629, 674, 681; Collins et al. 1995: 177; Ng 1998: 1065; McLay 1999: 427 –569; 2001b: 809; McLay & Ng 2004: 1 –24; McLay & Ng 2005: 15; Martin & Davis 2001: 74; Davie 2002: 167; Schweitzer et al. 2003: 18; Schweitzer & Feldmann 2005: 21, 22, tables 1, 4; Guinot & Tavares 2001: 525, 529, 531; 2003: 112, 115, 120; Guinot & Quenette 2005: 282; Poore 2004: 308; Števċiċ 2005: 18; De Angeli & Garassino 2006: 29; Beschin et al. 2007: 20; Ng et al. 2008: 37.

Dynomeninae A. Milne-Edwards & Bouvier 1902 pro parte: 22.

Remarks. McLay’s (1999) diagnosis of the family is accurate in most points. However, some aspects need modification or elaboration, and new characters described in this study should be added. For instance, the abdomen, instead of being “folded loosely under the thorax” ( McLay 1999: 468), is actually firmly held in Acanthodromia by coxal structures on mxp3 and P1–P3. In Acanthodromia , the abdominal somites are not “freely movable” ( McLay 1999: 536), but there is fusion of somites 3–6. Admittedly, it is difficult to determine the degree of abdominal fusion. Although traces of sutures are still visible in places, they are concealed by numerous spines. In any case, somites are functionally ankylosed in the specimens examined so far. To this effect, I follow Ng et al. (2008: 14) in that “we here regard fusion as segments which are immobile and cannot articulate with each other, regardless of whether the sutures are visible” at varying degrees.

Some characters are redefined and added.

Orbits either elongate, deep, obliquely arranged or shorter, shallower, more transversal. Frontal margin variously projecting. Posterior margin of carapace rather concave. Mxp3 more or less opercular; basis and ischium of endopod fused but suture distinct, either complete or not. Narrow shield formed by sternites 1 and 2 or 1–3; following thoracic sternites either completely included between coxae of pereopods or with narrow lateral portion intercalated between abdomen and pereopods; sternum forms a plate that regularly declines posteriorly; sternite 8 tilted, located in another plane than preceding ones. Anterior sternites 1, 2 small, fused into a narrow shield, either pentagonal, onion-shaped or, more rarely, triangular; stacking up of anterior sternites may be recognised by location of gynglymes for articulation of mxp1–mxp3 along thick margin of shield ( Figure 4A ). Sternite 3 either clearly distinct, visible (plesiomorphy), or represented at base of shield by short band, of about same width as sternite 4 in its anterior part (apomorphy); suture 3/4 indicated by change of level, straight or convex, or marked by denticulate crest. Sternites 4–7 (except episternites) fused into undivided plate, with parallel margins, medially forming flat area, varying from moderately wide to wide. Sternal sutures 4/5–6/7 hardly visible, hidden by borders of sterno-coxal depressions; suture 4/ 5 may be medially replaced by convex line; suture 7/8 present, even in males, relatively short in both sexes. Sterno-abdominal depression deep, completely covered by male abdomen over entire length and width, or shallow, not well defined, always with medial flat floor. Deep sterno-coxal depressions present at level of P2–P4 ( Figures 2 A, B, 4A). Male abdomen either long, narrow, completely accommodated in sterno-abdominal depression, or shorter, relatively broad even in males, flexible; telson reaching base of mxp3 or level of mid-sternite 4; lateral margins of abdomen (uropod margin included) may be slightly modified ( Acanthodromiinae n. subfam., Paradynomeninae n. subfam.), and not modified in the two other subfamilies. Abdomen with somites 1–6 free or with somites 3–6 fused in both sexes (at least in Acanthodromia margarita ), sutures still partially visible. Abdominal holding either firm in both sexes and involving coxae of mxp3 and P1–P3 ( Acanthodromiinae n. subfam.), or less so but still fairly tight ( Paradynomeninae n. subfam.), or loose and performed by a structure which is either coxal (Metaynomeninae n. subfam.) or sternal ( Dynomeninae ). Sexual dimorphism of abdominal somite 6 correlated with sexual dimorphism of uropod. Vestigial pleopods present on male somites 3–5, biramous (two rami either equal or, more often, unequal, exopodite being longer than endopodite); exceptionally ( Dynomene praedator A. Milne-Edwards, 1879 ), pleopods 3–5 uniramous; thus pleopodal formula complete ( Figure 3 B). Uropods as dorsal plates ( Figure 5 ), varying from small, slightly mobile to well developed, immobile (even at so great extent that penultimate abdominal somite excluded from reaching abdominal lateral margin), usually not prominent in males (slightly prominent in Paradynomeninae n. subfam.), may be sexually dimorphic (larger in females). Apertures of spermathecae ending well apart from each other, slightly behind female gonopore on P3 coxa. Chelipeds usually equal, may be unequal at least in males, and homomorphic, slightly dimorphic sexually (however with marked growth and modifications in large males of Dynomene praedator ). P5 strongly reduced, not movable, directed obliquely between posterolateral margin of carapace and P4; basis-ischium free or fused to merus; subchelate mechanism involving dactylus opposed to distal extension of propodus, sexually dimorphic, more developed, more spinous in females. P5 coxa modified in males, extended in long projection enclosing most of penis ( Figure 4 C–F). Endophragmal skeleton with junction between phragmae formed by fusion; skeletal parts variously layered (cf. Secretan 2002). Gills (cf. McLay 1999) usually 19 (including 6 podobranchs) + 7 epipods, with basically phyllobranchiate structure, but plates very variable in shape and number of epibranchial lobes.

Figures

FIGURE 2. Acanthodromia A. Milne-Edwards, 1880 (Acanthodromiinae n. subfam.). A – C, Acanthodromia erinacea A. Milne-Edwards, 1880, ovigerous female, 14.7 x 12 mm, west of Puerto Rico (USNM 124263). A, thoracic sternum; B, ventral surface without abdomen; C, abdomen. D, Acanthodromia margarita (Alcock, 1899), male, 11.6 x 12.8 mm, Balicasag Island, Panglao, Bohol, Visayas, Philippines, McLay & Ng det. (MNHN-B 28812) [The abdominal sutures are erroneously too much pronouced in these figures since there is a fusion of abdominal somites 3 – 6]. cx 1 – cx 5, coxae of P 1 – P 5; d 5 – d 6, sterno-coxal depressions 5 and 6; g, female gonopore; 2 – 6, sternites 2 – 6 (1 and 2 fused into shield; 3, individualised thoracic sternite 3; 3 / 4, limit between thoracic sternites 3 and 4; 4 / 5 – 5 / 6, thoracic sternal sutures 4 / 5 – 5 / 6 (indistinct); 7 / 8, distinct thoracic sternal suture 7 / 8. Scale bars: 2.5 mm.

FIGURE 3. Metadynomeninae n. subfam. (A, B) and Dynomeninae Ortmann (C, D), views of thoracic sternum and abdomen (A, C, D) and ventral surface of abdomen (B). A, Metadynomene tanensis (Yokoya, 1933), male 12, 5 x 13, 5 mm, New Caledonia, SMIB 2 (MNHN-B 25583): abdominal holding by P 2 coxa; B, Metadynomene crosnieri McLay, 1999, holotype, male, 23.2 x 22.7 mm, western Indian Ocean, îles Glorieuses, Benthedi Exp. (MNHN-B 22510): biramous vestigial pleopods 3 – 5; detail at right; C, Dynomene hispida (Latreille, in Milbert 1812), male 6.9 x 8.8 mm, New Caledonia (MNHN-B 22091): abdominal holding mechanism by sternal structure; D, Hirsutodynomene spinosa (Rathbun, 1911), male, 14.3 x 16.4 mm, western Indian Ocean, îles Glorieuses (MNHN-B 6899): abdominal holding mechanism by sternal structure (see Bouchard 2000: fig. 24 A). a 3 – a 6, abdominal somites 3 – 6; cx 1 – cx 4, coxae of P 1 – P 4; e 4 – e 6, episternites 4 – 6; pl 3 – pl 5, vestigial pleopods on abdominal somites 3 – 5; pr, coxal projection; s, shield; t, telson; u, uropod; 4, sternite 4. Scale bars: 1 mm.

FIGURE 5. Uropods in the four dynomenid subfamilies (dorsal surface, unless mentioned otherwise). A – H, Dynomeninae Ortmann, 1892; I – L, Metadynomeninae n. subfam.; M – N, Paradynomeninae n. subfam.; O – P, Acanthodromiinae n. subfam. A – B, Dynomene hispida (Latreille, in Milbert 1812): A, male, New Caledonia (MNHN-B 22091); B, female (After McLay 1999: fig. 18 g). C, Dynomene pilumnoides Alcock, 1900, female (After McLay 1999: fig. 21 g). D, Dynomene praedator A. Milne-Edwards, 1879, male (After McLay 1999: fig. 19 g). E, Dynomene pugnatrix De Man, 1889, male (After McLay 1999: fig. 22 g). F, Dynomene filholi Bouvier, 1894, male (After McLay 1999: fig. 20 g). G, Hirsutodynomene spinosa (Rathbun, 1911), male (After McLay 1999: fig. 23 g). H, Hirsutodynomene ursula (Stimpson, 1860), female (After McLay 1999: fig. 24 g). I – J, Metadynomene tanensis (Yokoya, 1933): I, male, New Caledonia, dorsal surface (MNHN-B 25583); J, female, ventral surface (After McLay 1999: fig. 27 g). K – L, Metadynomene crosnieri McLay, 1999, male, holotype, western Indian Ocean, îles Glorieuses (MNHN-B 22510): dorsal (K) and ventral (L) surfaces; M – N, Paradynomene sp., New Caledonia (MNHN-B 24779); M, male: ventral surface; N, female: dorsal surface (After McLay 1999: fig. 32 g). O, Acanthodromia erinacea A. Milne-Edwards, 1880, female, Puerto Rico (USNM 124263); P, Acanthodromia margarita (Alcock, 1899), female (After McLay 1999: fig. 31 f).

FIGURE 4. A – B, Dynomene hispida (Latreille, in Milbert 1812), A, male, 8.8 x 11.5 mm, New Caledonia (MNHN- B 22091): A, thoracic sternum, two views (arrow indicates difference in level); B, female, 8.3 x 10 mm, New Caledonia (MNHN-B 22091): posterior view showing sutures 7 / 8 and spermathecal apertures. C – F, P 5 coxa, enclosing penis for its most part. C, Dynomene hispida (Latreille, in Milbert 1812), male, 8.8 x 11.5 mm, New Caledonia (MNHN-B 22091). D, Paradynomene sp., male, 11 mm width, New Caledonia (MNHN-B 24780); E, Hirsutodynomene ursula (Stimpson, 1860), male, 9.6 x 11.7 mm, Galápagos Is. (MNHN-B 27637); F, Metadynomene tanensis (Yokoya, 1933), male, 12.5 x 13.5 mm, New Caledonia, SMIB 2 (MNHN-B 25583). cx 1 – cx 4, coxae of P 1 – P 4; d 5 – d 7, sterno-coxal depressions on sternites 5, 6 and 7; e 4 – e 6, episternites 4 – 6; gmxp 1 – gmxp 3, gynglymes of mxp 1 – mxp 3; p, penis; pr, projection; s, spermatheca; 3 – 8, sternites 3 – 8; 4 / 5 – 6 / 7, thoracic sternal sutures 4 / 5 – 6 / 7 (indistinct); 7 / 8, distinct thoracic sternal suture 7 / 8. Scale bars: 1 mm (A, B, D); 0.5 mm (C, E, F).