taxonID	type	description	language	source
E16737583844FFA2B4DEFAA8FEA0E885.taxon	description	FOSSIL GENERA. — Goniocypoda Woodward, 1867 (type species by monotypy: G. edwardsi Woodward, 1867); Palaeopinnixa Via, 1966 (type species by original designation: P. rathbunae Schweitzer, Feldmann Tucker & Berglund, 2000; originally Pinnixa eocenica Rathbun, 1926, see Schweitzer et al. 2000).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583844FFA2B4DEFAA8FEA0E885.taxon	discussion	REMARKS Hexapodid crabs were often regarded as having sternal male genital openings (Barnard 1950: 283, key; Balss 1957: 1658). The family was assigned either to the Thoracotremata (or Catometopa) (Guinot 1978 provisionally; Schram 1986; Schweitzer et al. 2000; von Sternberg & Cumberlidge 2001) or to the Heterotremata (Guinot 1979; Saint Laurent 1989; Guinot & Richer de Forges 1997; Guinot & Bouchard 1998; Martin & Davis 2001), the latter implying a true coxal condition of the male openings. Hexapodids are considered as highly modified and specialized. Many species are known to live in annelid tubes or on hydroids. Tesch (1918: 238) commented that their commensalistic mode of life “ has brought about not only the cylindrical shape of the body, but also the disappearance of the posterior legs, which, by the fact that they are inserted at a higher level than the preceding pairs, perhaps would rather impair the animal’s moving up and down in the tubes of Annelids and Hydrozoa ”. The P 5 were presumed to be absent in all Hexapodidae, except in Paeduma. Thus, the corresponding sternite 8 was supposedly also lacking. Sternite 8 was seen as a triangular piece remaining visible dorsally (Barnard 1950: 300, fig. 56 g, k, under “ sternite 5 ”). A line dividing it into two parts has been observed in Hexapus stebbingi Barnard, 1947 (Gordon 1971: figs 1, 2). The hypothesis that a portion of the reduced sternite 8 may have an appendicular origin was formulated by Guinot (1979: 115, fig. 32). In fact, sternite 8 is present, although markedly reduced and concealed under the abdomen, with only a very small exposed portion. P 5 vestigial coxae were clearly indicated, but not figured, by Saint Laurent (1989: 154, footnote). Such a vestigial coxa was confirmed by several dissections of Hexaplax megalops Doflein, 1904 by Guinot, Tavares & Castro (unpublished data), and it is supposedly characteristic to all Hexapodidae. The presence of a vestigial P 5 coxa, from which the penis emerges, has necessitated a new interpretation of the hexapodids, which are no longer hexapods in term of anatomy (at least the males) but are clearly true decapods. Male Hexapodidae actually have five pairs of legs, with an extremely reduced P 5 which lacks all its articles except for the vestigial coxa, which is concealed under the abdomen. Genera within the Hexapodidae are essentially distinguished by the shape of the eyes and mxp 3, the shape and degree of fusion of the male abdomen, the development of sternal grooves on the thoracic sternum, the frequent presence of a stridulating apparatus (in the family at least two different shapes of one of its two components), and the structure of the G 1. Some characters, such as the G 1, show such a wide range of variation that subfamilies could be considered. In addition to the dorsal location and reduction of sternite 8 and the partial loss of P 5 in males, the Hexapodidae show other characteristics that are not found in most other Eubrachyura Saint Laurent, 1980: loss of the exopodite of pleopods of somite 2 in females, persistence of structures for the abdominal maintaining in adult females, and female abdomen not markedly sexually dimorphic. Guinot & Quenette (2005: 334, fig. 29 b) discussed the possible relationships of the Hexapodidae with other eubrachyuran families characterized by reduced P 5, in particular the Retroplumidae Gill, 1894, females of which show the same features (loss of the exopodite of pleopods of somite 2 in females, persistence of structures for the abdominal maintaining in adult females) as the Hexapodidae.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	description	(Figs 1; 2)	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	materials_examined	TYPE SPECIES. — Amorphopus cylindraceus (Bell, 1859), by monotypy. Amorphopus Bell, 1859 is an invalid junior homonym of Amorphopus Audinet-Serville, 1838 (Insecta), therefore was replaced by Paeduma Rathbun, 1897 (p. 163), substitute name, from the Greek “ rudiment ” in allusion to the fifth pair of legs (Rathbun 1897: 163, footnote). Genus Paeduma: gender neuter according to Manning & Holthuis (1981), thus the type species is Paeduma cylindraceum (but gender masculine according to Huang et al. 2002, who are not followed in the present paper). EMENDED DIAGNOSIS (male holotype of P. cylindraceum). — Body thick, nearly cylindrical, narrowing anteriorly, markedly convex, transversely flattened. Dorsal surface with regions indistinct, grooves not marked except for extremely weak traces of cervical and branchiocardiac grooves. Lateral margin arcuate anteriorly, then divergent, posteriorly convergent. Front depressed, relatively narrow (6.4 times in carapace width), with distinct thickened ridge, more advanced laterally than in midline, with very weak, obtuse projection medially. Antennae with articles 2 + 3 covered by antennules. Epistome relatively developed. Orbits transverse, situated in straight line, not dorsally expanded, rimmed. Eyes movable, small, lying transversally, with cornea small, narrower than stalk. Buccal cavity with sides convergent anteriorly. Mxp 3 of “ normal ” type (i. e. operculiform), broad, nearly filling entire field. Endopod with broad ischion and merus; anteroexternal margin of merus oblique; propodus, carpus and dactylus slender; palp cylindrical; dactylus longer than propodus but extending only two-thirds of ischion, close to its border. Exopod wide, with long but concealed flagellum (not shown in Fig. 2 C). Thoracic sternum very wide. Sternites 1 - 2 forming a narrow, triangular piece extending between bases of mxp 3, clearly separated from sternite 3; sternite 3 distinct but not delimited by suture; sternite 4 much developed; sternites 5 - 7 similarly developed, high; sternite 8 not aligned with preceding sternites, strongly reduced, only visible dorsally as small, ornamented plate inserted between sternite 7 and abdominal somite 1. Episternites 4 - 5 similarly elongated, pointed; episternites 6 - 7 similarly rounded; episternite 7 forming projection overhanging posterolateral angle of carapace. Sutures 4 / 5 to 6 / 7 nearly parallel, equidistant. Sternal grooves or trenches absent. Sterno-abdominal cavity elongated, reaching sternite 3. Male abdomen very long, extending beyond bases of mxp 3, extremely narrow, specially at level of somite 6 and telson; strong constriction at level of abdominal somite 6 opposite to middle part of thoracic sternite 5. Somites 1, 2 free, approximately similar in size; somites 3 - 5 fused, forming distally-truncated triangle; somite 6 as extremely long, linear, undivided piece; its proximal part markedly constricted; telson elongated, rounded at tip. Gonopods concealed under abdomen, shape unknown (dry condition of specimen). G 1 supposedly relatively slender (because of narrowness of abdomen), not recurved posteriorly or doubled recurved into a 8 - shaped figure; G 2 probably small. Chelipeds markedly unequal in male, robust, thick; large cheliped with palm nearly as long as wide, gap between fingers; fingers armed with blunt teeth; small cheliped with closer fingers. Dactyli on each side with striae on inner surface. P 2 - P 4 short, rather similar in size, shape. P 5 not visible on the outside, reduced to a vestigial coxa in males, absent in females. Stridulating apparatus of two striated parts. Pterygostomian region with an oblique row of rather thick, short, spaced sticks (about 14), progressively diminishing in size to show externally as rounded granules; dactylus provided with numerous thin, long, closed striae on whole length of inner surface (except for apex).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	description	GEOGRAPHICAL DISTRIBUTION. — Galápagos Islands (Garth 1946, 1991; Hickman & Zimmerman 2000) or possibly Pacific coast of South America.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	discussion	REMARKS Bell’s Amorphopus (= Paeduma) was established without indicating locality and without figures, which may explain why Paeduma cylindraceum was never reported since its description. The P 5 was considered a “ mere rudiment, in the form of a minute tubercle inserted in a little notch at the base of the first joint of the fourth pair, and scarcely discernible by the naked eye ” (Bell 1859: 28). Bell did not believe that a leg could vanish completely in a decapod. De Haan (1835: 35, under Hexapus sexpes Fabricius, 1798) correctly remarked: “ Nullum indicium quinti paris, neque sub abdomine ulli reconditi ” (= “ no sign of a fifth pair, or is any hidden under the pleon ”). Stebbing (1910: 315) corrected Bell’s statement “ six pairs of legs beside the claws ” to “ three pairs of legs ”. Two of Bell’s statements need comment. 1) The location of the P 5 rudiment showing as a tubercule at the base of the P 4 does not correspond to the normal place of the coxa of an appendage (always articulated on the sternite). This location, which might be interpreted as the result of the displacement of the P 5 in the reduction processus of sternite 8, does not match with the interpretation of an hexapodid P 5 vestigial coxa that is concealed under the abdomen (Saint Laurent 1989; Guinot, Tavares & Castro unpublished data). 2) A similar “ tubercle ” was seen by Bell (1859: 29) at the base of the P 4 in dorsal view of Hexapus sexpes (Fabricius, 1798) figured by De Haan (1835: pl. D, pl. 11, fig. 6). The small figure of De Haan (1835: pl. 11, fig. 6) does not allow to be sure of the presence of such a tubercle, but the presence in H. sexpes of a structure similar to that of P. cylindraceum is confirmed here. Bell’s “ mere rudiment ” on the P 4 coxa of P. cylindraceum (Figs 1 A; 2 D) actually corresponds to the external portion of the apodeme of the P 4 coxa, i. e. the apodemal platelet. It is exposed in a notch of the proximal border of the P 4 coxa, and shows externally as a calcified strip extending through the arthrodial cavity as usual. The apodemal platelet is clearly visible in the dry holotype of P. cylindraceum, as well as in a number of hexapodids (for instance in Hexapus sexpes). The supposed P 5 rudiment seen by Bell (1859) definitely is not a vestige of P 5, but corresponds to a portion of the P 4. Actually, apodemal platelets are present on P 2 - P 4 coxae in all the hexapodid genera that were examined, although this could not be confirmed in the holotype of P. cylindraceum because of its dry condition. The apodemal platelets are also visible ventrally on the basis-ischion of P 2 - P 4 in the P. cylindraceum ’ s holotype as well as in other hexapodids. Such apodemal (coxal and ischio-basal) platelets are present to a variable extent on P 2 to P 5 in other eubrachyuran families. It seems, however, that the coxal platelets are particularly well visible on the pereopods of the Hexapodidae, and on the P 4 in particular. Authors such as Huang et al. (2002) who have discussed other species of Paeduma, viz. P. orientalis, unfortunately have not provided enough information. As previously mentioned, Manning & Holthuis (1981) gave erroneous characters for Paeduma because they combined the characters briefly provided by Bell (1859) for P. cylindraceum, the type species, and those shown by the two other species of Paeduma, P. orientalis and P. chuenensis. The latter two are herein placed in Hexalaughlia n. gen. Manning & Holthuis (1981) indicated for Paeduma “ third and fourth and fourth [sic] and fifth male abdominal somites fused ” (p. 168, in the key) and “ third and fourth and fifth and sixth somites fused ” (p. 173, 175). We put another interpretation, hypothetically: abdominal somites 3 - 5 fused in Paeduma and in Hexalaughlia n. gen. Manning & Holthuis’ (1981) assertion that the gonopods of Paeduma are slender and recurved posteriorly is applicable to the gonopods of Hexalaughlia n. gen. The gonopods of Paeduma (P. cylindraceum) are unknown because of the dry condition of the A B holotype, but they are probably neither recurved posteriorly nor doubly recurved into an 8 - shaped figure as in Hexalaughlia n. gen. Bell’s (1859) description of P. cylindraceum does not mention pterygostomian stridulating striae, which explains why this character is missing in the generic diagnosis of Paeduma provided by Manning & Holthuis (1981: 173: “ pterygostomian region lacking oblique striae ”). Manning & Holthuis attributed to Paeduma two other species, P. orientalis and P. chuenensis, that lack a stridulating apparatus. In contrast, Manning & Holthuis (1981: 177) did characterize Stevea williamsi by the presence of stridulating pterygostomian striae, a condition confirmed herein.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	materials_examined	MATERIAL EXAMINED. — Holotype, ♂ 15.3 × 23.5 mm, dry and in good condition, with Bell’s handwritten labels: “ Amorphopus ” (placed above specimen) and “ Am: cylindraceus male sign. Gallapagos [sic] Mr Cuming ” (placed below specimen). Registration number: OUMNH 15693 (S. De Grave pers. comm.).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	description	DESCRIPTION OF DRY MALE HOLOTYPE Granules absent on dorsal surface of carapace, present only on lateral borders, more developed at level of P 4; with numerous pits except medially. Large cheliped with palm much inflated; outer surface covered by coarse, rounded granules, more numerous on inferior half near superior border; proximal superior border of dactylus coarsely granulated, prehensile margin armed with two distinct blunt teeth; fixed finger curved, granulated, prehensile margin armed with strong proximal tooth and less distinct teeth; marked gap between fingers. Small cheliped much reduced; no marked gap between pointed fingers; outer surface of palm covered by coarse, blunt granules, closer on inferior half near superior border; dactylus with superior bor- der coarsely granulated except distally, prehensile margin armed with several triangular teeth; fixed finger with two rows of strong granules, prehensile margin armed with several triangular teeth. Thoracic sternum ornamented with marked granules along border of sterno-abdominal cavity and sutures; surface punctate. Sutures 4 / 5 to 6 / 7 equidistant; sternites 1 - 2 advanced between mxp 3; sternite 3 distinct but not demarcated by suture; sternite 4 well developed, with latero-anterior projections; sternites 5 to 7 inflated, of about same size. Sternite 7 tilted, its posterolateral corner (episternite 7) forming a marked projection which fits with a notch on border of carapace (interlocking mechanism carapace / sternum). Sternite 8 present but extremely reduced and concealed under carapace, except for small plate exposed dorsally, calcified, ornamented. Pereopods 2 - 4 with margins of meri ornamented with salient, blunt granules. Setae on surfaces of P 2 and P 3 meri, on surfaces of P 2 - P 4 carpi and propodi; longer setae on margins of distal articles. P 4 coxa with a markedly discernible apodemal platelet; ischio-basis with a ventral apodemal platelet. P 5 vestigial coxa concealed under abdomen.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	discussion	REMARKS The particular spelling of Galápagos, with a double “ l ”, i. e. “ Gallapagos ”, is consistent on labels of Bell’s dry collection (see DiMauro 1982: 158: a fact which “ does help substantiate that it is Bell’s collection ”), and was similarly used by H. Milne Edwards (1838: 12). It should be stressed that the Galápagos origin of this unique specimen must be taken with caution because of a possible exchange of labels between material collected by Cuming in the Galápagos and along the South American mainland coast. Several species collected by Cuming and reported by Bell “ have been turned up along the mainland coast of south America from Santa Elena Bay, Ecuador, to the Bay of Panama, localities also visited by Cuming ” (Garth 1946: 343; see also Garth 1958: 71; DiMauro 1982: 156).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	materials_examined	TYPE SPECIES. — Hexapus williamsi Glassell, 1938, by original designation. SPECIES INCLUDED. — One extant species, S. williamsi. For the status of the fossil species Stevea cesarii Beschin, Busulini, De Angeli & Tessier, 1994, from the Eocene of Italy, see Fossil Hexapodidae.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	description	DESCRIPTION See Manning & Holthuis (1981: 168, 177), in amending the features concerning the male abdomen which, instead of “ second through sixth somites fused ”, shows weak but distinct sutures.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	discussion	REMARKS The genus Stevea was established by Manning & Holthuis (1981) to separate from Hexapus De Haan, 1835 emend. (type species: Cancer sexpes Fabricius, 1798; genus established in 1833 but without nominal species) the American species H. williamsi Glassell, 1938 (p. 445, pl. 35, figs 1 - 4). Stevea williamsi appears to be known with certainty from the male holotype only, 5.8 × 8.6 mm, from San José, Guatemala (SDSNH No. 3940; ex Cat. No 1158). The female 9.4 × 14.4 mm, from the Gulf of Tehuantepec, west coast of Mexico (USNM 170897), identified to H. williamsi, may well prove to belong to Paeduma, a direct comparison with the holotype of H. williamsi being necessary. Glassell (1938: 445, pl. 35, fig. 4) illustrated the male abdomen of S. williamsi as having several weak sutures; however, this does not correspond exactly to his text: “ Only the 1 st and 7 th segment [telson] are articulated; the five interior segments are coalesced ”. This is probably why Manning & Holthuis (1981) indicated for Stevea “ male abdomen with three somites, second through sixth fused ”. Examination of the male holotype and photographs by L. L. Lovell (Fig. 3 B, C) indicate that Glassell’s sketch, showing several abdominal sutures, is correct. The abdominal somites of the holotype (which are wider than in Paeduma) are separated by several weak but visible sutures so that in Stevea abdominal somites seem to be distinct, although all not articulated. There is no constriction. In these respects S. williamsi appears to be distinct from P. cylindraceum where, hypothetically, the abdominal somites 3 - 5 are completely fused and where there is a marked constriction at the level of somite 6, leaving an empty space on each side (Fig. 2 B, E). The first gonopods of the male holotype of S. williamsi are essentially straight, with only a slight distal curvature (L. L. Lovell pers. comm.). Because of the dry condition of the holotype of P. cylindraceum, it is not possible to compare the gonopods to those of Stevea. In S. williamsi the meri of P 2 - P 4 show rows of tubercles, those on P 2 being more numerous (L. L. Lovell pers. comm.). A stridulating apparatus similar to that of Paeduma (Fig. 2 A, B) is mentioned in Manning & Holthuis’ (1981: 177) diagnosis of Stevea. According to Glassell (1938: 445, pl. 35, fig. 2), in S. williamsi there is “ a tubercle on the inner distal face [of the palm of the cheliped] which engages with the stridulations of the epimera ”. Actually, in both sexes of Stevea, the symmetrical rows of thick and spaced pterygostomian stridulating striae are more likely rubbed by very thin and closed striae located on the inner part of the dactylus of both chelipeds, as in P. cylindraceum. In the female of S. williamsi (USNM 170897) the exposed portion of sternite 8 is small, as in the male of P. cylindraceum (Fig. 2 B, E). Despite some similar features, P. cylindraceum and S. williamsi are distinct. The question of the specific versus generic level of these differences, which concern mainly the male abdomen and the gonopods, is beyond the scope of this study, and should be addressed in a revision of the family Hexapodidae. Two genera, Paeduma and Stevea, are thus so far known from the Pacific coast of South America. See below for the fossil record of Stevea.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	materials_examined	MATERIAL EXAMINED. — Holotype, ♂ 5.8 × 8.6 mm, San José, Guatemala (SDSNH No. 3940; ex Cat. No. 1158; examined and photographed by L. L. Lovell and W. A. Newman; with reservation, ♀ 9.4 × 14.4 mm, Gulf of Tehuantepec, west coast of Mexico (USNM 170897).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E16737583842FFAFB6E5FC75FC7AEE49.taxon	description	DESCRIPTION See Glassell (1938) and above.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384FFFABB531FA29FE3FE8A5.taxon	description	(Fig. 4)	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384FFFABB531FA29FE3FE8A5.taxon	materials_examined	TYPE SPECIES. — Thaumastoplax orientalis Rathbun, 1909, by present designation. OTHER SPECIES INCLUDED. — Thaumastoplax chuenensis Rathbun, 1909.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384FFFABB531FA29FE3FE8A5.taxon	etymology	ETYMOLOGY. — It is a pleasure to dedicate this new genus to Dr Patsy A. McLaughlin, in recognition of her considerable contribution to scientific knowledge. Gender: feminine. GEOGRAPHIC DISTRIBUTION. — Western Pacific.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384FFFABB531FA29FE3FE8A5.taxon	description	DESCRIPTION Carapace wider than long, longitudinally convex, transversely flat. Dorsal surface with regions indistinct, except for a faint H-shaped median depression; gastric region may be sharply outlined. Lateral margin anteriorly arcuated, then straight (not diverging), sometimes marked by raised line. Antennae not covered by antennules. Front slightly deflected, thin. Epistome reduced. Orbits oval, in common straight line, not dorsally expanded, rimmed. Eyes movable, small, transversal, with small cornea. Buccal cavity much broader than long, anteriorly arcuated, sides anteriorly divergent. Mxp 3 somewhat pediform, slender, inclined, gaping, leaving mxp 2 only partly visible. Endopod with short, mesially expanded ischion; merus narrow, inclined; carpus short; propodus as long as broad, considerably dilated and with mesial expansion distally; dactylus lanceolated, with very long setae entering sternoabdominal cavity. A wide hiatus between palp and ischium, partly filled by fringes of setae. Exopod without flagellum. Pterygostomian region without row of stridulatory striae. Thoracic sternum wide. Sternites 1 - 2 forming wide, triangular piece extending between bases of mxp 3, prolonging into sternite 3 without marked delimitation; sternite 4 much developed; sternites 5 - 7 similarly developed, high; sternite 8 reduced, visible dorsally only as minute plate inserted between sternite 7 and abdominal somite 1, most part hidden under carapace. Episternites 4 - 5 similarly elongated, pointed; episternites 6 - 7 similarly rounded, episternite 7 forming projection overhanging the posterolateral angle of carapace (interlocking apparatus). Sutures 4 / 5, 5 / 6 and 6 / 7 nearly equidistantly parallel. Sternal grooves or trenches absent in both sexes. Sternoabdominal cavity elongated, reaching sternite 3. Male abdomen very long, extending beyond bases of mxp 3, moderately narrow, specially at level of somite 6 and telson; no marked constriction at level of somite 6. Somites 1, 2 free, of about the same size, not much elongated transversally; somites 3 - 5 fused in undivided piece, anteriorly narrowing; somite 6 as relatively long plate; telson relatively short, bluntly triangular. Abdomen not maintained by prominences of press-button type [to be verified], appearing maintained between oblique slopes of deep sterno-abdominal cavity. Gonopods concealed under abdomen, slender, recurved posteriorly, apex apparently naked. Chelipeds equal in male, short; palm of large cheliped higher than long, may be ornamented with granules. P 2 - P 4 markedly unequal, with P 3 granulous, very developed, longer, thicker (in particular the merus) than subequal, smooth P 2, P 4; all articles fringed with long, thick setae. No stridulating apparatus.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384FFFABB531FA29FE3FE8A5.taxon	discussion	REMARKS The recent discovery of the holotype of P. cylindraceum (Bell, 1859), type species of the American genus Paeduma, has allowed its comparison with two other species described from Thailand and referred to Paeduma by Manning & Holthuis (1981: 173). As a result, a new genus, Hexalaughlia n. gen., is established for those two species: H. chuenensis (Rathbun, 1909) n. comb., and H. orientalis (Rathbun, 1909) n. comb. Hexalaughlia n. gen. may be distinguished from Paeduma by the following characters: mxp 3 pediform, slender, endopod recurved, with dilated ischium and propodus, and exopod without flagellum (Fig. 4 A) (mxp 3 operculiform, endopod with narrow propod, exopod with flagellum in Paeduma, Fig. 2 C); stridulating striae lacking (row of oblique striae in Paeduma, Fig. 2 A, C); thoracic sternum with sternites 1 - 3 forming a triangular piece, without marked delimitation (Fig. 4 B) (a narrow triangle in Paeduma, Fig. 2 B); male abdomen markedly wider in Hexalaughlia n. gen. than in Paeduma (where it appears somewhat linear); somite 6 moderately long, without constriction in Hexalaughlia n. gen. (Fig. 4 B-D) (somite 6 as very long, narrow, basally constricted plate in Paeduma, A Figs 1 B; 2 B); telson rather short, bluntly triangular in Hexalaughlia n. gen. (elongated and rounded at tip in Paeduma); chelipeds equal in Hexalaughlia n. gen. (strong heterochely in Paeduma); P 2 - P 4 markedly unequal, with P 3 stout, much larger than P 2 and P 4, ornamentated with strong granules in Hexalaughlia n. gen. (P 2 - P 4 subequal, nearly similar in size and shape, and weak ornamentation in Paeduma, Fig. 1). Contrary to Manning & Holthuis’ (1981) assertion, Paeduma does not resemble Thaumastoplax. In contrast, Hexalaughlia n. gen. is close to Thaumastoplax by its pediform and recurved mxp 3 (Fig. 4 A), the absence of a flagellum on mxp 3 exopod, absence of stridulating pterygostomian striae, and unequal P 2 - P 4. Hexalaughlia n. gen., however, differs from Thaumastoplax by the narrower carapace; the relative size of the ambulatory legs, the P 2 and P 4 being subequal and P 3 much stouter (P 2 slender, P 3 very stout and P 4 thicker than P 1 in Thaumastoplax); G 1 recurved posteriorly and 8 - shaped (slender, only sinuous, with apex directed anteriorly in Thaumastoplax).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384BFFABB500FD36FC03EF87.taxon	discussion	REMARKS	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384BFFABB6D7FC55FC1AE940.taxon	description	(Fig. 4)	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384BFFABB6D7FC55FC1AE940.taxon	materials_examined	MATERIAL EXAMINED (specific identification with reservation). — Japan. From Kobe, Tomaga Shima Lt., Albatross, stn 4964, 65 m, 34 ° 05 ’ 30 ’’ N, 134 ° 56 ’ 40 ’’ E, 27. VIII. 1906, Thaumastoplax orientalis, ♂ 5.5 × 8 mm (USNM 46392).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384BFFABB6D7FC55FC1AE940.taxon	discussion	REMARKS It was not possible to examine the type material of Thaumastoplax orientalis from Thailand. The Albatross Japanese specimen bears a label from R. B. Manning indicating that it represents a new species. Mannning & Holthuis (1981: 174) add that this genus also includes “ … a species from Japan, identified by earlier workers with T. [Thaumastoplax] orientalis, which we believe represents a new species, the description of which is in preparation ”. The first occurence outside Thailand was by Sakai (1934). There are several other Japanese records (see Sakai 1976; Takeda 1982), although that material should be examined to see if it actually represents H. orientalis n. comb.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384BFFA9B48FFB6BFC2AEA1C.taxon	description	A key of extant and fossil Hexapodidae and similar genera, including both Paeduma and Stevea, was provided by Schweitzer & Feldmann (2001: 337, 344, 345; see also Schweitzer 2005: 289). The distinctive characters of Stevea given by Schweitzer & Feldmann (2001: 337) were according to the erroneous diagnosis of Manning & Holthuis (1981), as previously explained. Most references to Paeduma in the literature (except for the mention of the type species, P. cylindraceum) correspond to Hexalaughlia n. gen.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384BFFA9B48FFB6BFC2AEA1C.taxon	description	The nearly complete loss of P 5 is a problem in recognizing fossil hexapodids because the legs, in particular P 5, are often lost during fossilisation. Among the criteria that could be used are the shape of sternites 5 - 7 (well developed, equal and subrectangular) and the strong reduction of sternite 8, and perhaps even without visible trace. Several fossil crabs truly lacking P 5 (instead of lost during fossilisation) have been attributed to the Hexapodidae. The first verified occurence for this condition was for the Paleocene Goniocypoda rajasthanica Glaessner & Rao, 1960. More recently, G. tessieri Rémy & Tessier, 1954, from the Maastrichtian, has been confirmed as another fossil member of the Hexapodidae (see Crane 1981; Crane & Quayle 1986; Schweitzer & Feldmann 2001; Feldmann & Schweitzer 2004; Schweitzer 2005). Morris & Collins (1991), who described Prepaeduma decapoda Morris & Collins, 1991 from the Pliocene, considered Prepaeduma to be an ancestor to Paeduma in which P 5 was not yet fully suppressed (Schweitzer et al. 2000: 55). Beschin et al. (1994) justifiably doubted the placement of Prepaeduma in the Hexapodidae. Finally Schweitzer & Feldmann (2001: 335, 339) clearly demonstrated that the type material of the Pliocene P. decapoda was a composite. The holotype (Morris & Collins 1991: fig. 56), without preserved pereopods, exhibits the seven sternites that are diagnostic of the Hexapodidae (in particular the well developped and similar sternites 5 - 7). Conversely, the paratype, which has a small but visible P 5 (Morris & Collins 1991: fig. 57), has been referred to Orthakrolophus bittneri (Morris & Collins, 1991), of the Chasmocarcininae Serène, 1964 (Collins et al. 2003: 218, pl. 7, fig. 2). Collins et al. (2003: 220, pl. 7, fig. 8) provided a revised description of the true Prepaeduma decapoda, and referred it to Hexapus. Hexapus decapodus is a true hexapodid, with well visible seven thoracic sternites only, and shows five or six long stridulating ridges on the pterygostomian regions, typical of Hexapus (e. g., H. sexpes). For a discussion of the fossil representatives of Thaumastoplax, see Imaizumi (1959) and Collins & Morris (1976, 1978).	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
E1673758384BFFA9B48FFB6BFC2AEA1C.taxon	discussion	REMARKS ON THE HEXAPODID STRIDULATING APPARATUS The stridulating apparatus consists in Paeduma of a prominent, narrow, and oblique row of rather thick striae on the pterygostomian region (Fig. 2 A, B), and thin striae on the inner surface of the dactyl of both chelipeds. The same kind of stridulating mechanism is present in Hexaplax Doflein, 1904 (Doflein 1904; Tesch 1918; see also Guinot-Dumortier & Dumortier 1960: 122, plectrum erroneously indicated on the propodus). The pars stridens and plectrum are well differentiated and consist of specialized striae, although in Hexaplax the distinction between these two structures lacks precision. In Stevea williamsi, thick and spaced pterygostomian striae are rubbed by thin and closed striae on the inner part of the dactylus of both chelipeds, as in P. cylindraceum. The fossil Stevea cesarii shows a similar stridulating pterygostomian row of striae. A slightly distinct stridulating mechanism exists in a few other Hexapodidae. In Hexapus sexpes for instance, there is an area with several oblique and elongated striae disposed near the anterolateral angles of the buccal cavity; they are rubbed by thin, closed striae on the inner surface of the dactyl of both chelipeds (A. Milne-Edwards 1873: 254, pl. 12, fig. 1 a; Tesch 1918: 240; Guinot-Dumortier & Dumortier 1960: 130, fig. 9; Manning & Holthuis 1981: fig. 32 b; Manning 1982: 159, fig. 1 d). Fossil Hexapus species probably show an area of oblique pterygostomian striae, as in Hexapu s pinfoldi Collins & Morris, 1978, from Eocene of Pakistan, with 14 oblique and postero-laterally directed pterygostomial striae, sometimes irregularly arranged (Glaessner & Secretan 1987: 8, pl. 1, figs 5 b, 6; Beschin et al. 1994: 194). A similar area exists in the extant Lambdophallus sexpes Alcock, 1900, but the striae seem to be fewer and thicker (Alcock 1900: 330; Alcock & McArdle 1903: pl. 62, fig. 1 a). Hexalaughlia orientalis n. comb. and H. chuenensis n. comb. lack a stridulatory apparatus. A stridulating apparatus was described as a prominent ridge in Goniocypoda edwardsi Woodward, 1867 and probably also in G. quaylei Crane, 1981, both from the Upper Eocene of Hampshire (Crane 1981: 6, 7, fig. 8 D). This is an additional character supporting assignment of Goniocypoda Woodward, 1867 to the Hexapodidae.	en	Guinot, Danièle (2006): Rediscovery of the holotype of Paeduma cylindraceum (Bell, 1859) and description of a new genus of Hexapodidae (Decapoda, Brachyura). Zoosystema 28 (2): 553-571, DOI: 10.5281/zenodo.5401414
