Published March 31, 2026
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TABLE 1. — Morphological differences between Cardisomatidae n in Formal establishment of Gecarcinoidea H. Milne Edwards, 1837 n. stat. (Crustacea, Decapoda, Brachyura), with recognition of two families, Cardisomatidae n. fam. and Gecarcinidae restrict., and new insights on Epigrapsidae Watabe, 2007
Authors/Creators
- 1. Institut de Systématique, Évolution, Biodiversité (ISYEB), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, case postale 53, 57 rue Cuvier, F- 75231 Paris cedex 05 (France)
- 2. Direction générale déléguée aux Collections, Muséum national d'Histoire naturelle, case postale 53, 57 rue Cuvier, F- 75231 Paris cedex 05 (France)
Description
TABLE 1. — Morphological differences between Cardisomatidae n. fam. and Gecarcinidae restrict.
| Morphological characters | Cardisomatidae n. fam. | Gecarcinidae restrict. |
|---|---|---|
| Carapace | moderately swollen or marquedly swollen | very swollen to strongly swollen |
| Lateral striae | if present, faint, and more often absent | distinct, numerous |
| Fronto-orbital border | more than half width of carapace | half or less than half width of carapace |
| Front | relatively wide, not much deflexed | relatively narrow, strongly deflexed |
| Orbits | developed, transversally elongated | small and deep, more or less oblique or sometimes very small and englobed in carapace (Gecarcinus ruricola) |
| Eyestalks | elongated, completely filling orbits (Cardisoma, Tuerkayana) or not (Discoplax) | short, more or less curved |
| Proepistome | more or less prominently and dome-shaped, variously sized, exposed | very small, not completely covered by subfrontal plate, therefore visible (Gecarcinus), or completely covered by subfrontal plate, therefore hardly discernible (Hartnollius, Gecarcoidea, Johngarthia) |
| Buccal frame | elongate-subquadrate, well delineated laterally with wide, thick, straight anterior margin | shorter, quadrate, subcircular or rhomboid, not delineated laterally |
| Epistome: anterior margin | as two concave edges joining medially | linear |
| Mxp3 | long | shorter |
| Mxp3 palp | normal, with three mobile articles externally visible | with first article fused to merus internal surface and with two mobile distal articles either concealed, not visible (Gecarcinus), or more or less visible (other genera) |
| Mxp3 exopod | exposed, slender, with concealed flagellum | conspicuously reduced to more or less narrow plate, completely concealed; flagellum lost |
| Pterygostomial area | setose | glabrous |
| Sterno-pleonal cavity | deep, with developed lateral slopes | less deep, shallow |
| Ridge (when pleon is well applied) | marked (Cardisoma, Tuerkayana) or faint (Discoplax), running along telson and also extending along distal part of pleonal somite 6 | marked, only running along telson |
| Pleonal locking structures in males | obscure or absent, non-functional | an oblique prominence, marked (Gecarcoidea, Gecarcinus) to very marked (Johngarthia) in middle of sternite 5. A button more or less close to suture 4/5 (Hartnollius). Apparatus non-functional |
| Male gonopore | sternal but emerging very close to P5 coxo-sternal condyle and membrane lining arthrodial cavity | distant from to P5 coxo-sternal condyle, widely sternal |
| Penis | penis emerging just at origin of suture 7/8, above P5 coxo-sternal condyle (except in Discoplax) | penis emerging rather far from P5 coxo-sternal condyle, at level of suture 7/8, thus in a more sternal position |
| Female pleon | relatively narrow, oval, and, thanks to dense fringe of setae on margins, completely filling thoracic sternum except for episternites; telson small and narrow, reaching more or less sternite 3 and mxp3, leaving only a reduced lateral portion exposed | much wider, discoid, leaving laterally and especially anteriorly a sternal portion exposed, in addtion to the episternites; telson in the shape of a large triangle |
| Male and female pleons G1 | bordered by thick fringe of setae along margins long, slender, tip reaching sternal suture 4/5 or not quite reaching it | bordered by narrow fringe of setae along margins short, thick; calcified part reaching about middle part of sternite 6 (Gecarcinus, Hartnollius), slightly behind (Gecarcoidea, Johngarthia) |
| Vulvae | vulvae on sternite 6 just below suture 5/6; sternal cover salient, developed (Cardisoma), smaller (Tuerkayana), or flat (Discoplax) | protruding, obliquely directed, normally occluded by rigid calcified immobile operculum |
| Setal tufts | no tufts of hydrophilic setae along first pleonal somites; setae on posterior margin of sternite 7 | setal tufts of hydrophilic setae along first pleonal somites; setae on posterior margin of sternite 7, slightly on P5 coxae |
| Stridulatory apparatus | absent, except in Discoplax with suborbital ridge acting as pars stridens; plectrum on inner margin of cheliped merus | only signalled in Hartnollius laterali s: subhepatic and pterygostomial striae as pars stridens; inner surface of palm of chelae used as plectrum; perhaps also functional in other genera of Gecarcinidae, but not documented |
Notes
Published as part of Paula, Danièle Guinot & Moreno, Paula A. Rodríguez, 2026, Formal establishment of Gecarcinoidea H. Milne Edwards, 1837 n. stat. (Crustacea, Decapoda, Brachyura), with recognition of two families, Cardisomatidae n. fam. and Gecarcinidae restrict., and new insights on Epigrapsidae Watabe, 2007, pp. 219 in Zoosystema 48 (8) on page 219, DOI: 10.5252/zoosystema2026v48a8, http://zenodo.org/record/19501195
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