Hartnollius quadratus ( Saussure, 1853 ), 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 : 291-294

Hartnollius quadratus ( Saussure, 1853) n. comb.

( Figs 9B ; 10C, F ; 11C ; 13C ; 14 ; 16 ; 20 ; Table 1 )

Gecarcinus quadratus Saussure, 1853: 360 , pl. 12 fig. 2. — Stimpson 1857: 29. — Rathbun 1910: 591; 1918, 358, fig. 162, pls 121, 122 (material from ‘Turbo, Colombia’ corresponds likely to H. lateralis n. comb., see below). — Finnegan 1931: 653. — Pesta 1931: 180, pls 5, 6. — Garth 1948: 12, 58, fig. 2. — Bott 1955: 65. — Bright 1966: 190, fig. 4G. — Bright & Hogue 1972: 20. — Powers 1977: 140. — Brusca 1980: 297, 302, fig. 20. — Prahl et al. 1984: 29. — Sherman 2002: 67, 70, seq. — Griffiths et al. 2007: 219-224, figs 1, 2. — Arzola-González & Flores-Campaña 2008: 45. — Ng et al. 2008: 215. — Felder et al. 2009: 1004. — Perger & Wall 2014: fig. 6DF. — Christy & Wada 2015: fig. 71-8.10. — Toledano-Carrasco 2016: 146, 148, 149; 2019: 22, figs 10B, 11E-H, 12K-O, 13J-P, 17A-L, 18A-L, 19A-L, 20G-H, R-X. — Köhnk et al. 2017: 2110, fig. 19c, d. — Hartnoll et al. 2017: 959. — Toledano-Carrasco & Villalobos Hiriart 2018: 67. — Guinot et al. 2018: 568, 569, 567, 589. — N. K. Ng et al. 2019: 99, 100. — Toledano-Carrasco et al. 2021: 215 , 216, 221, 224, 226, 228, 229, 230, 231, figs 1B, 2D-H, 3C, E, 4-6, 8, tables 1-3.

Nec Gecarcinus (Gecarcinus) lateralis quadratus – Türkay 1970: 335, 338, fig. 4. — Prahl 1981: 207: fig. 56.1. — Prahl & Manjarrés 1984a: 155, 166, figs 3, 5.3 (= Gecarcinus nobilii Perger & Wall, 2014 ).

Geocarcinus lateralis – Young 1900: 239 (nec Gecarcinus lateralis Fréminville in Guérin, 1832).

Gecarcinus lateralis – Perger & Wall 2014: 97 (nec Gecarcinus lateralis Fréminville in Guérin, 1832).

Nec Gecarcinus quadratus – Prahl et al. 1990: 29 (= Gecarcinus nobilii Perger & Wall, 2014 ).

TYPE MATERIAL. — Syntype. Mexico • 1 ♂ cl 39.7 mm; Mazatlán [M. Verreaux]; ANSP CA3741 . Perhaps another one ♂ syntype of which only a small cheliped is preserved .

MATERIAL EXAMINED. — Mexico • 1 ♀ 39.4 × 49.7 mm; dry; Oaxaca; rev. M. Türkay VI.1972 det. Gecarcinus (Gecarcinus) lateralis ; MNHN-IU-2000-3759 (= MNHN-B3759 ) • 2 ♀ 40.0 × 51.0 mm, 40.6 × 53.0 mm; dry; MNHN-IU-2000-3761 (= MNHN-B3761 ) ;

Gecarcinus quadratus • 1 ♂ 50.0 × 64.0 mm; in ethanol; Estero El Verde Camacho, Sinaloa; 12.VII.1972, M. Hendrickx det. 1998 Gecarcinus quadratus ; MNHN-IU-2017-8391 (= MNHN-B20900 ). Unknown location ( Gabon?:incorrect location) • 1 ♂ 47.0 × 62.7mm, 1 ♀ 42.4 × 52.7 mm; dry; M. Verreaux; det. Gecarcinus quadratus ; Türkay Rev. VI.1972 Gecarcinus lateralis ; MNHN-IU-2000-3762 (= MNHN-B3762 ) .

TYPE LOCALITY. — Mazatlán ( Mexico).

DIAGNOSIS

Carapace

Carapace smaller than that of Gecarcinus ruricola but larger than that of Hartnollius lateralis n. comb., broader than long, relatively flat, with hepatic, subhepatic and branchial regions only slightly inflated; widest part of carapace being in line with antero-lateral angles of mesogastric region. Carapace front about as wide as distance between mesial ends of suborbital cristae. Dorsal surface with shallow grooves: cervical groove terminating anteriorly in a pit near orbital angle; median (or urogastric) groove and longitudinal mesogastric groove rising towards frontal margin. Fronto-orbital distance about half or a little less than one half of maximum carapace width in adults. Front short, broad, moderately produced and deflexed, widening very little below, its inferior margin being slightly arcuate. Numerous striae along lateral margins of the carapace, used as stridulatory pars stridens. Mesial lobe of infraorbital margin angular, just joining front edge and completely exposed. Antero-lateral margins entire, rounded, joining exorbital angle, with more or less marked junction, smooth in males; delineated by granular row in females.

Cephalic structures

Antennules very small, folded obliquely. Antennae very short, completely exposed. Eyestalks relatively short, curved.

Proepistome, epistome and pterygostome

Proepistome covered by subfrontal plate. Epistome developed, with one median crest and a lateral crest on each side, setose. Buccal cavity rhomboid. Subhepatic and pterygostomial region glabrous, with many striae.

Mxp3

Mxp3 rather small, reaching epistome, leaving between them a narrow rhomboid gap, in longitudinal position. Ischium and merus subequal, with their articulation only slightly obliquely directed; ischium barely smaller than merus, without longitudinal groove (only a small trace); merus slightly directed obliquely, anterior margin straight, without distinct emargination, at the very least barely concave, or showing only discontinuity or even having very small notch; meri of both sides practically joining medially; palp inserted below merus: palp with first article fused to merus internal surface and with only small portion of mobile distal article exposed. Exopod of mxp3 as narrow plate, completely concealed by fringe of thick setae, apex not reaching ischium-merus articulation; without flagellum.

Chelipeds

Male chelipeds massive but not extraordinarily enlarged, very unequal especially in largest males, not widely gaping; heterochely variable, usually slightly marked; occlusal margins of fingers with small, spaced teeth on both sides; in case of greatly heterochely, pronounced heterodonty. In adults, merus with only small granules and carpus smooth on inner lower margin. Inner surface of palm of chelae used as stridulatory plectrum by rubbing on pterygostomial striae (pars stridens).

Female chelipeds subequal or nearly so, moderately gaping, therefore sexual dimorphism moderate.

Ambulatory legs

P3 moderately spiny. Propodus with unequally developed lateral carinae bearing four rows of weakly developed spines. Dactylus with six rows of small unequal spines, with 5 rows in juveniles.

Sterno-pleonal cavity and pleon

Sterno-pleonal cavity moderately setose, short, not close to sternal suture 2/3, with marked ridge around telson. Male pleon moderately long, bell-shaped; with all somites free plus telson; lateral margins only with fringe of setae; somite 6 with gently convex lateral margins, forming lateral shoulder; telson equilateral triangle-shaped, narrower than posterior margin of somite 6, lateral margins slightly concave.

Female pleon subcircular; telson forming isosceles triangle, as wide as or slightly narrower than posterior margin of somite 6, lateral margins straight, smooth.

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 slightly convex margins; suture 2/3 present, practically straight or barely concave and only forming an obtuse angle; suture 3/4 absent, without lateral trace; sternites 3 + 4 completely fused, with concave margin at level of articulation of P1 and convex at junction of mxp3; 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; deep median line only along sternite 7.

Locking pleonal structure as prominence covered by setae, rather close to suture 4/5; corresponding pleonal sockets not delineated, so pleonal locking no longer functional (see also Köhnk et al. 2017: 2112).

Setal tufts 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, apex short, with unequal setae at its tip; laterally, a very long, narrow, horny, unfolded, curved tube, open over 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.

COLOUR

Sex independent colour dimorphism: in males and females, purplish, red, white, with variously coloured spots, intense purple chelipeds and light yellow or orange legs ( Fig. 20 ). For more details, see Perger & Wall (2014: 101, figs 4, 5D) and Toledano-Carrasco (2019: 24, fig. 10B).

REMARKS

According to the original description and figure of G. quadratus by Saussure (1853: 360), there is no notch on the anterior margin of the mxp3 merus, so that Hartnollius quadratus n. comb. ( Fig. 10C ) shares with Gecarcinus ruricola ( Fig. 10A ) a slightly similar aspect of this region. In fact, in H. quadratus n. comb., the margin is either straight ( Rathbun 1918: fig. 162) or discontinuous, and may even have a small notch. The margin of the mxp3 merus of a Mexican male specimen MNHN-IU-2017-8391 (= MNHN-B20900) is asymmetric: straight on one side and very slightly emarginate on the other side ( Figs 10C ; 14A, B ).

Whereas Rathbun (1918: 358) indicated that the type of Gecarcinus quadratus was in the ‘Geneva Mus.’, it was in ’Phil. Acad’ according to Stimpson (1857: 29). No specimen is found in the MHNG collection ( Hollier 2018). Although not in the list of Spamer & Bogan (1994), according to Boyko (2000: 128) there are parts of one male syntype cl 39.7 mm, from Mazatlán, deposited at the ANSP under the number ANSP CA3741, which contains also a detached male cheliped from perhaps one of two now-lost ANSP specimens.

According to Sherman (2002, as Gecarcinus quadratus ), in the Costa Rica’s Corcovado National Park, Hartnollius quadratus n. comb. lives in fossorial populations, with up to six crabs per square meter in the coastal forest extending about 600 m inland from the Pacific Ocean. H. quadratus n. comb. affects plant diversity in a Neotropical continental rain forest by selective seedling consumption. According to Griffiths et al. (2007, as Gecarcinus quadratus ), in the same location it is an engineering species that controls nutrient cycling in tropical forests: during the dry season, the density of land crab burrows decreases with distance from the ocean, so that H. quadratus n. comb. is restricted to a narrow coastal zone with a sandy substrate; this distribution could have profound effects on plant community structure.

GEOGRAPHICAL DISTRIBUTION

Hartnollius quadratus n. comb. is found along the American Pacific coast, ranging from the eastern shores of the Gulf of California in Mexico, Nicaragua, Costa Rica ( Villegas-Retana & Picado-Masís 2021), Panama (Prahl et al. 1984; Hendrickx 1995; Cuesta et al. 2007; Perger & Wall 2014; Toledano-Carrasco 2019; Toledano-Carrasco et al. 2021). The records of Gecarcinus quadratus by Rathbun (1910: 591; 1918: 358) ‘Turbo on Atlantic side of Colombia’ refer to as H. lateralis n. comb. The H. quadratus n. comb. from Peru previously reported by Türkay (1970: 338) may belong to H. nobilii (see below, under this name). It is important to note that the Pacific G. lateralis between the Darien province ( Panama) and the Choco dept. ( Colombia) may refer to H. nobilii n. comb. ( Perger & Wall 2014).

Figures

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. 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. 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. 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.