Hartnollius, Paula & Rodríguez & Atzimba & Toledano-Carrasco, 2025

Paula, Danièle Guinot, Rodríguez, Paula A., Atzimba, Moreno I. & Toledano-Carrasco, Atzimba, 2025, The charismatic Gecarcinus ruricola (Linnaeus, 1758), type species of Gecarcinus Leach, 1814, with a neotype designation and genetic data, and new generic assignment, Hartnollius n. gen., for the three remaining species of the genus (Crustacea, Brachyura, Gecarcinidae), Zoosystema 47 (16), pp. 261-314 : 284-286

Genus Hartnollius n. gen.

( Figs 5 , 9 ; 10B, C, E, F ; 11B, C ; 12-16 ; 19 ; 20 ; Table 1 )

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RESTRICTED CHRESONYMY

All previous mentions of Gecarcinus species in the literature that do not refer to G. ruricola according to the diagnosis above should be designated as Hartnollius n. gen. The list below only contains the references related to Gecarcinus sensu lato (unless they concern G. ruricola ) and/or to one or other of the species reported to it, i.e., G. lateralis , G. quadratus and G. nobilii , which should henceforth be known as Hartnollius lateralis n. comb., H. nobilii n. comb. and H. quadratus n. comb.

The chresonymy presented below in the form of a list has been restricted in view of the numerous taxonomic articles published on Gecarcinidae and also those dealing with the numerous aspects of land crabs (ecological, behavioural, embryological, physiological, biological). We did not take into account the species of Gecarcinus attributed to Johngarthia before its establishment by Türkay (1970).

Gecarcinus – Stebbing 1893: 79, 80. — Türkay 1973: 84. — Hartnoll et al. 2006b: 198. — Tavares & Faria 2010. — Hartnoll 2015: 404. — Luque 2017: 153. — Schweitzer et al. 2023: 2.

Geocarcinus and Geocarcinus lateralis – Young 1900: 233, 238.

Gecarcinus and Gecarcinus lateralis – Rathbun 1901: 14; 1921: 79; 1924: 19; 1936: 388. — Bliss 1968: 357, 359, 360, et seq., figs 2, 6, 7, 9, 10, 12. — Guinot 1979: 123, 136 et seq. and p. 214. — Rodríguez 1980: 402, 403, fig. 110, pl. 68. — Britton et al. 1982: 207. — Powers & Bliss 1983: 272, 289 et seq. — Abele & Kim 1986: 61, 661, 663. — Türkay 1987: 145. — Adamczewska & Morris 2000: 708. — Hartnoll et al. 2006b: 203, 211; 2014: 531, 536, 537 and 535. — Guinot et al. 2013: 109, 254, 266.

Gecarcinus lateralis – Saussure 1858b: 24. — Desbonne, in Desbonne & Schramm 1867: 42. — Verrill 1908: 308. — Chace & Holthuis 1948: 26. — Chace 1956: 159. — Cabrera 1966: 173-187. — Bliss et al. 1978: 113-151, figs 6, 7-11, 14-31. — Savazzi 1985: 147-153, figs 1A, 2A, 3A, B, 4, 5A, B. — Abele & Kim 1986: 61, 661, 663. — Scelzo & Varela 1988. — García et al. 1998: 27, table 1. — Guinot & Bouchard 1998: 669. — Capistrán-Barradas et al. 2003: 323. — Carré 2005: 23. — Vaslet et al. 2013: 245, annex 3. — Yokoyama 2013: 114, fig. p. 115. — Questel 2014: 11; 2019: 25, 33, unnumbered figs. — Davie et al. 2015a: 61, fig. 71-2.30C. — Poupin 2018: 223; 2024: 138 . — Hernández-Aguilera et al. 2022: 204.

Gecarcinus quadratus – Stimpson 1857: 29. — Garth 1948: 9, 58, fig.2. — Hendrickx 1995: 139. — Christy & Wada 2015: fig.71-8.10.

Gecarcinus and Gecarcinus quadratus – Brusca 1980: 297, 302, fig. 20. — Prahl & Manjarrés 1984b: 6.

Gecarcinus laterali s and G. quadratus – Türkay 1973: 973, fig. 2, 969. — Powers 1977: 139, 140. — Griffiths et al. 2007: 219 et seq. — Felder et al. 2009: 1088, 1104. — Marin & Tiunov 2023: 113, 117, table 4.

Gecarcinus , G. lateralis and G. quadratus – Rathbun 1918: 351, 355, 358. — Bright & Hogue 1972: 1, 6, 20, 21, 48. — Prahl & Manjarrés 1984a: 151, 154, 155. — Türkay 1970: 335, key. — Burggren & McMahon 1988: all mentions of Gecarcinus species except those concerning G. ruricola . — Tavares 1989: 3, 40, 54 and 58; 1991: 213; 2002: 333, fig. 3. — Ng & Guinot 2001: 333. — Cuesta et al. 2007: 263. — Ng et al. 2008: 215. — Hartnoll et al. 2017: 947 and 949.

Gecarcinus lateralis and G. nobilii – N. K. Ng et al. 2019: 99 , fig. 2F.

Gecarcinus , G. laterali s, G. quadratus and G. nobilii – Perger & Wall 2014: 94 , 96. — Guinot et al. 2018: 550 , 561, 568. — Toledano-Carrasco 2016: 28, 32, 37-39, 118, et seq., table 1. — Toledano-Carrasco & Villalobos Hiriart 2018: 67. — Toledano-Carrasco et al. 2021: 225 , 226, figs 1, 2, 3.

TYPE SPECIES BY PRESENT DESIGNATION. — Gecarcinus lateralis Fréminville in Guérin, 1832 (see Low et al. 2013: 104; N. K. Ng et al. 2019: 99).

OTHER INCLUDED SPECIES. — Gecarcinus quadratus Saussure, 1853 ; G. nobilii Perger & Wall, 2014 .

ETYMOLOGY. — Named in honour of Richard G. Hartnoll, who provided several important and valuable works on the Gecarcinidae , particularly on their biology, and notably on Gecarcinus ruricola . Furthermore, and not least, Richard has been, from the beginnings until today, a source of inspiration for the first author, who wishes to express her immense admiration for him. Gender masculine.

DIAGNOSIS

Carapace

Carapace broader than long, flat, with hepatic, subhepatic and branchial regions not markedly inflated, widest part of carapace being more or less in line with antero-lateral angles of mesogastric region. Fronto-orbital distance about half of maximum carapace width in adults. Dorsal surface with shallow grooves: cervical groove terminating anteriorly in a pit near orbital angle; median (or urogastric) groove well-defined but shallow; longitudinal mesogastric groove well-defined but shallow, rising towards frontal margin. Numerous striae along lateral margins of the carapace, used as stridulatory pars stridens. Front short, moderately produced and deflexed, with straight lateral margins and upturned lower margin. Mesial lobe of infraorbital margin angular, just joining front edge, completely exposed. Antero-lateral margins rounded, not delimitated in males; marked by granular margin in females.

Cephalic structures

Antennules very small, folded obliquely. Antennae very short, completely exposed. Orbits typical, outer angle marked. Eyestalks relatively short, curved.

Proepistome, epistome and pterygostome Proepistome covered by subfrontal plate, thus not visible. Epistome developed, with one median crest and a lateral crest on each side. Buccal cavity rhomboid. Subhepatic and pterygostomial region glabrous, with many striae.

Mxp3

Mxp3 rather small, not reaching epistome (except in H. quadratus n. comb.), leaving between them a narrow rhomboid gap, in which mandibles are exposed. Ischium in longitudinal position and merus only slightly obliquely directed, their articulation nearly horizontal. Ischium barely smaller than merus, without longitudinal groove (only a small trace); merus directed slightly obliquely, with anterior margin emarginate but variably, sometimes only slightly, barely concave ( H. quadratus n. comb.) or with distinct notch; meri of both sides not joining medially (except in H. quadratus n. comb.); palp inserted below merus: its first article fused to merus internal surface and with only small portion of last mobile article exposed. Exopod of mxp3 completely concealed, apex not reaching ischium-merus articulation, as narrow suboval plate; without flagellum.

Chelipeds

Male chelipeds massive but not extraordinarily enlarged, very unequal, especially in old males; heterochely and heterodonty usually not or only slightly marked; in rare cases of greatly uneven chelipeds (heterochelic chelae), a more pronounced gap and pronounced heterodonty. No genetic predisposition for right-handedness. Merus smooth ( H. lateralis n. comb.) or with only small granules on inner lower margin ( H. quadratus n. comb., H. nobilii n. comb.); carpus smooth ( H. lateralis n. comb., H. quadratus n. comb.) or with denticles ( H. nobilii n. comb.) on inner upper margin; occlusal margins of fingers with small, spaced teeth on both sides. Sexual dimorphism moderate.

Ambulatory legs

P3 moderately spiny. Propodus with unequally developed lateral carinae bearing four rows of weakly developed spines. Dactylus with four rows of small equal spines ( H. lateralis n. comb., H. nobilii n. comb.) or with six rows of small unequal spines ( H. quadratus n. comb.).

Sterno-pleonal cavity and pleon

Sterno-pleonal cavity moderately setose, short, not close to thoracic sternal suture 2/3, with marked ridge around telson. Male pleon moderately long, with all somites free plus telson; somite 6 with more or less convex lateral margins. Margins of pleon only with fringe of setae.

Thoracic sternum, locking pleonal structures and setal tufts Thoracic sternum wide, narrowing at level of somite 5, thus restricted at level of P1. Sternite 1 as small triangular tooth, not separated by suture from sternite 2, not recessed; sternite 2 semi-ovate with convex margins; suture 2/3 present, practically straight or barely concave, in open V-shaped ( H. lateralis n. comb.); suture 3/4 absent, without lateral trace; sternites 3 + 4 completely fused, with gently concave or nearly straight margins; sutures 4/5 to 7/8 interrupted; sternites 5-7 similarly shaped, sutures well defined; suture 7/8 rather short; sternite 8 not developed medially, totally hidden when pleon is folded; posterior emargination reaching sternite 7 at level of narrow median bridge at level of suture 7/8; another weak median bridge at level of suture 6/7 ( H. lateralis n. comb., H. quadratus n. comb.); deep median line only along sternite 7.

Locking pleonal structure as prominence rather close to suture 4/5, covered by setae; pleonal sockets not delineated, so pleonal locking no longer functional.

Patches of more or less dense hydrophilic setae located along first pleonal somites margins of pleon and at its junction with carapace.

Male gonopore and penis

Male gonopore and penis at level of suture 7/8 emerging rather far from P5 coxo-sternal condyle.

G1 and G2

G1 slightly tapering at its extremity, with unequal setae at its tip; apex short; laterally, a very long, narrow, horny, more or less curved tube, not folded and open all along, and exceeding G1 tip; several horny setae at its base.

G2 very small, without flagellum.

Vulvae

Protruding, oriented nearly horizontally, normally occluded by rigid calcified immobile operculum.

Figures

FIG. 5. — Specimens from mainland America identified by Rathbun as Gecarcinus ruricola (Linnaeus, 1758), but being in fact Hartnollius lateralis (Fréminville in Guérin, 1832) n. comb. A, B, ♂ 32.3 × 40.5 mm, Florida, Florida Keys, Loggerhead Key, USNM 71219: A, general dorsal view; B, ventral view; C, D, ♂ 32.4 × 44.2 mm, Nicaragua, Greytown, Rathbun det. Gecarcinus ruricola; labels by Carson and Barnwell indicating G. lateralis, USNM 74612; C, general dorsal view; D, ventral view. Scale bars: 10 mm. Credits: MNHN-Soubzmaigne.

FIG. 9. — Hartnollius n. gen., general views:A, H. lateralis (Fréminville in Guérin,1832) n. comb.,♂ 42.0 × 56.0 mm,Guadeloupe, MNHN-IU-2017-8390 (= MNHN- B24656); B, H. quadratus (Saussure, 1853) n. comb., ♂ 50.0 × 64.0 mm, Mexico, MNHN-IU-2017-8391 (= MNHN-B20900). Scale bars: 20 mm. Credits: MNHN- Soubzmaigne.

FIG. 10. — A-C, frontal views,D-F, chelipeds:A, Gecarcinus ruricola (Linnaeus,1758),neotype,♂ 55.0 × 76.0 mm,Cuba,MNHN-IU-2017-8392 (= MNHN-B13155); B, Hartnollius lateralis (Fréminville in Guérin, 1832) n. comb., ♂ 43.0 × 55.0 mm, Mexico, CNCR 35126; C, Hartnollius quadratus (Saussure, 1853) n. comb., ♀ 36.0 × 46.0 mm, Mexico, CNCR 24607; D, Gecarcinus ruricola (Linnaeus, 1758), neotype, ♂ 55.0 × 76.0 mm, Cuba, MNHN-IU-2017-8392 (= MNHN-B13155): see granules on margins of merus and carpus of chelipeds; E, Hartnollius lateralis n. comb., ♂ 43.0 × 55.0 mm, Mexico, CNCR 35126: see smooth margins of chelipeds; F, Hartnollius quadratus (Saussure, 1853) n. comb., ♂ 43.0 × 55.0 mm, Mexico, CNCR 34630: see smooth margins of chelipeds. Scale bars: 10 mm. Credits: A, D, MNHN-Soubzmaigne; B, C, E, F, CNCR-Toledano-Carrasco.

FIG. 11. — Mxp3, internal view, and palp: A, Gecarcinus ruricola (Linnaeus, 1758), Jamaica, MZUSP 18501 (ex USU-279); B, Hartnollius lateralis (Fréminville in Guérin, 1832) n. comb., Costa Rica, MZUSP 18509 (ex USU-281); C, H. quadratus (Saussure, 1853) n. comb., Mexico, MZUSP 18859 (ex AHF) (see Tavares 1989: fig. 14). Courtesy Marcos Tavares.

FIG. 12. — Hartnollius lateralis (Fréminville in Guérin, 1832) n. comb., ♂ 42.0 × 56.0 mm, Guadeloupe, MNHN-IU-2017-8390 (= MNHN-B24656): A, frontal view; B, front, orbit,and mesial lobe of infraorbital margin;C, front,proepistome (hidden), antenna (exposed) and mesial lobe of infraorbital margin; D, thoracic sternum and male pleon; E, F, external and internal views of chelipeds. Scale bars: A, D, E, F, 10 mm; B, C, 5 mm. Credits: MNHN-Soubzmaigne.

FIG. 13. — Harrtnollius n. gen.: gonopods and vulvae:A, B, Hartnollius lateralis (Fréminville in Guérin, 1832) n. comb., Guadeloupe, MNHN-IU-2017-8390 (= MNHN-B24656): A, ♂ 40.5 × 55.7 mm: G1, G2, caudal view; B, ♀ 32.6 × 41.8 mm:vulvae;C, H.quadratus (Saussure,1853) n.comb.,♂ 50.0 × 64.0 mm, Mexico, MNHN-IU-2017-8391 (= MNHN-B20900):G1, G2, caudal view. Scale bars: A, C, 2 mm; B, 1 mm. Credits: MNHN-Soubzmaigne.

FIG. 14. — Hartnollius quadratus (Saussure, 1853) n. comb., ♂ 50.0 × 64.0 mm, Mexico, MNHN-IU-2017-8391 (= MNHN-B20900): A, frontal view; B, front, proepistome (hidden), antenna (exposed) and mesial lobe of infraorbital margin; C, thoracic sternum and male pleon; D, E, external and internal views of cheli- peds. Scale bars: A, C, D, E, 20 mm; B, 2 mm. Credits: MNHN-Soubzmaigne.

FIG. 15. — Hartnollius nobilii (Perger & Wall, 2014) n. comb., paratype, ♀ 36.6 × 44.3 mm, Ecuador, MNHN-IU-2014-11211 (= MNHN-B12314): A, dorsal view; B, ventral view; C, front, orbit, and mesial lobe of infraorbital margin; D, front, proepistome (hidden), antenna (exposed), mesial lobe of infraorbital margin, and mxp3; E, thoracic sternum, female pleon and vulvae; F, left cheliped, internal view; G, chelipeds, external view; H, right P3; I, left P4. Scale bar: 10 mm. Credits: MNHN-Rodríguez Moreno.

FIG. 16. — Bayesian inference phylogenetic tree of Gecarcinidae based on the concatenation of mitochondrial COI and 16S rRNA gene fragments.Numbers at nodes are support values for BI (posterior probability) and ML (Ultrafast bootstrap). The clade of crabs with less terrestrial habits (Cardisoma Latreille, 1828, Discoplax A.Milne-Edwards,1867,and Tuerkayana Guinot,N. K. Ng & Rodríguez Moreno, 2018) are highlighted in purple,whereas the clade with markedly terrestrial habits (Gecarcinus Leach, 1814, Hartnollius n. gen. and Johngarthia Türkay, 1970) are highlighted in red. Ocypode rotundata Miers, 1882 was included as outgroup.

FIG. 19. — Hartnollius lateralis (Fréminville in Guérin,1832) n. comb., living and in the field:A, Guadeloupe,Marie-Galante, KARUBENTHOS 3, Stn IGM25,MNHN- IU-2024-5551; B, C, Guadeloupe, July 2015, on sand; D, E, Martinique, Anse à Prunes, forest about 65 m far from the shore, altitude about 2 m; D, crab bearing a branch; E, crab on a tree. Credits: A, L. Corbari-MNHN-ARBig-LPRig; B, C, J. Poupin; D, E, F. Lavail (planetedoc.com).

FIG. 20. — Living Hartnollius quadratus (Saussure,1853) n. comb.:A, Mexico,Chiapas,Barra de Boca del Cielo;B, ‘Halloween crab’,Costa Rica,Nosara,on a tree, 2006; C, Panama, on the beach, 2005; D, E, Mexico, Chacahua, La Grúa: two views. Credits: A, J. L. Villalobos Hiriart; B, Bhny, Creative Commons Attribution- Share-Alike License 3.0; C, Dozenist, Creative Commons Attribution-Share-Alike License 3.0; D, E, A. López-Velázquez.