Potamocarcinus magnus ( Rathbun, 1896 )

Magalhães, Célio & Wehrtmann, Ingo S., 2025, Taxonomic revision and distribution of the freshwater crabs of the family Pseudothelphusidae (Decapoda, Brachyura) from Guatemala, with the descriptions of two new species and keys to the species of all genera, Zoosystema 47 (26), pp. 581-615 : 585-587

Potamocarcinus magnus ( Rathbun, 1896)

( Figs 2; 13)

Pseudothelphusa magna Rathbun, 1896: 377 , fig. 1, 2; pl. 29, 30, figs 7-10; 1906: 502 (in list).

Potamocarcinus guatemalensis Rathbun, 1904: 242 ( nomen nudum).

Potamocarcinus guatemalensis Rathbun, 1905: 313 , text-fig. 101, pl. 14 fig. 7; 1906: 503 (in list). — Coifmann 1939: 110 (in list).

Potamocarcinus ( Potamocarcinus) magnus guatemalensis – Pretzmann 1965: 2 (in list); 1972: 70, figs 381-384, 396-398. — Smalley 1970: 102.

Potamocarcinus ( Megathelphusa) magnus guatemalensis – Pretzmann 1971: 20 (in list); 1980: 654.

Potamocarcinus magnus – Rodríguez 1982: 111, fig. 72c, e. — Villalobos F. 1982: 220 (in list). — Ng et al. 2008: 176 (part, in list). — Wehrtmann et al. 2014: 123, fig. 1C, D; 2016: 781 (in list). — Acevedo-Alonso & Cumberlidge 2022: 582 (Appendix 2, in list). — Villalobos Hiriart & Álvarez 2008: 297 (form, México, Guatemala, El Salvador) (in list).

TYPE MATERIAL EXAMINED. — Holotype. Guatemala • 1♂, holotype by monotypy of Potamocarcinus guatemalensis Rathbun, 1905 ; precise location unknown; M. Bocourt leg.; MNHN Entry 453-1883; MNHN-IU-2017-8050 (= MNHN-B5170 ).

MATERIAL EXAMINED. — Guatemala • 1 ♂; collecting data unknown; UVGCR 506 • 1♂, collecting data unknown; UVGCR 508 • 1♂ (65.4:41.6) 1 ♀ (64.9:43.1); Guatemala, Amatitlán lake delta [ 14°28’34”N, 90°34’35”W; 1190 m elev.]; date and leg. unknown; FMNH 1830 • 3 ♂ (43.5:29.0-81.3:-) 1 ♀ (damaged); Guatemala, Amatitlán market ; date and leg. unknown; FMNH 1825 • 1♂ (82.0:52.0); Guatemala, Lake Amatitlán [ 14°29’12”N, 90°36’38”W; 1190 m elev.]; 28.I-3.II.1906; S. E. Meek leg.; FMNH 1827 , • 1 ♂ (74.5:47.9); Guatemala, Lake Amatitlán [ 14°29’12”N, 90°36’38”W; 1190 m elev.]; 28.I-03.II.1906; S. E. Meek leg.; FMNH 1831 • 1♂ (56.8:37.3); Guatemala, Lake Amatitlán ; 26.VI.1906; S. E. Meek leg.; FMNH 1828 • 3♂ (45.3:30.0; 47.4:32.0; 1 damaged) 1♀ (45.0:30.4); Guatemala, Amatitlán [ 14°29’12”N, 90°36’40”W; 1190 m elev.], date and leg. unknown; FMNH 1832 • 1 immat. ♂; El Progreso, Río Morazán, near Morazán [ 14°55’54”N, 90°08’21”W; 349 m elev.], WNW of El Rancho, Motagua River basin ; 8.V.1947; Miller leg.; USNM 1089243 • 1 juv. ♂; Izabal, Río Ciénaga [ 15°40’50”N, 88°57’58”W; 13 m elev.], below bridge from road to Sarstún ; 18.III.1971; R. M. Boiley, R. C. & J. Lopez leg.; AMNH 8751 • 1 juv. ♂; Izabal, Río Ciénaga [ 15°40’50”N, 88°57’58”W; 13 m elev.], below bridge from road to Sarstún ; 18.III.1971; R. M. Boiley, R. C. & J. Lopez leg.; AMNH 16670 • 2 ♂ (51.7:37.0; damaged) 1 ♀ (24.9:17.2); Zacapa, Río Palmilla, near Usumatlán ; 14°58’30”N, 89°45’45”W; [ 245 m elev.]; 21.VII.2014; I. S. Wehrtmann & M. Orozco leg.; UCR-MZ uncat . • 1 ♂ (28.0:19.5) 2 immat. ♀ (31.7:21.7; 41.3:27.9); Zacapa, Río El Jutillo, near Usumatlán ; 14°59’19”N, 89°49’25”W; [ 347 m elev.]; 21.VII.2014, I. S. Wehrtmann & M. Orozco leg.; UCR-MZ uncat . • 1 ♂; Suchitepéquez, Río Choyolate [= Coyolate] [ 14°22’39.31”N, 91°08’13.14”W; 255 m elev.], Patulul; 21.V.1948; leg. unknown; USNM 189303 • 1 ♂; Solalá, Lago Atitlán [ 14°42’N, 91°12’W; 1558 m elev.]; 9.X.1993; J. Zunyge leg.; UVGCR 96 • 1 ♂; Solalá, Lago Atitlán ; 28.XI.1993; leg. unknown; UVGCR 379 • 1 ♂; Solalá, Lago Atitlán ; 6.XII.1984; J. Montúfar leg.; UVGCR 65 • 1♂; Solalá, Lago Atitlán ; 28.X.1993; E. Pacay leg.; UVGCR 417 • 1 ♂ (70.0:45.0); Solalá, Panajachel (bought in the market, captured at Lago Atitlán) ; VII.2013; I. S. Wehrtmann leg.; UCR-MZ 3114-02 • 1 juv. ♂; Escuintla, carretera a Puerto Quetzal [ 13°56’N, 90°47’W; 8 m elev.]; 1.XI.1993; C. Cardona leg.; UVGCR 319 .

DISTRIBUTION. — Guatemala ( El Progreso, Escuintla, Guatemala, Izabal, Solalá, Suchitepéquez, Zacapa) ( Fig. 13), Mexico, Belize, Honduras, El Salvador, Costa Rica ( Pretzmann 1980; Rodríguez 1982; Villalobos Hiriart & Álvarez 2008; Magalhães et al. 2015; Wehrtmann et al. 2016; this study).

OTHER RECORDS IN GUATEMALA. — Rodríguez (1982): Escuintla, Aguna [? Río Aguná, 14°15’05”N, 91°07’26”W, 97 m elev.]. Pretzmann (1980): Solalá, Lake Atitlán; Zacapa, Rio Cayo, 7.3 miles W Estanzuela ( 128.8 km E Guatemala City) [ 15°00’N, 89°34’W, 190 m elev.]; Guatemala, 45 km E Guatemala City, Río Platanos [ 14°50’42.25”N, 90°24’12.67”W, 495 m elev.]; Izabal, 2 km S Mariscos [ 15°24’54.53”N, 89°04’43.86”W, 8 m elev.], Lake Izabal drainage; Izabal, Río Sena near Seno, 7 miles NW Livingston [ 15°51’12”N, 88°50’53”W, 7 m elev.]. The mention of the department of Jalapa in Wehrtmann et al. (2016) must be corrected to department of El Progreso since this is the correct location of the record referred to lot USNM 1089243.

DESCRIPTION OF G1 ( Fig. 2 C-F)

Stout, straight in both caudal, mesial views, moderately compressed mesolaterally; caudal margin nearly straight in mesial view, with tuft of minute to short setae medially; lateral margin slightly concave distally in mesial view; caudal surface with sparce patch of caudal setae along median portion; mesocephalic surface with subdistal, elongated patch of setae increasing in size distally. Spermatic channel opening on apex cavity, situated towards lateral end at base of caudal process. Marginal suture on mesial surface, straight along most of stem, gently curved to lateral side distally in mesial view, with row of large marginal setae proximally. Marginal process broadly rounded, as long as caudal process in mesial view, partially overlapping this lobe on its lateral side. Lateral suture incomplete, marked by somewhat deep sulcus on first 3/4 of caudal surface. Mesial process as strong subtriangular projection directed cephalad on distal portion of mesial border. Apex moderately distorted in cephalic direction; caudal process enlarged, subquadrate in mesocaudal view, bearing slight protuberance on cephalic end, folded over the apex cavity, partially covering field of apical spines. Apex cavity oblong; field of apical spines moderately developed, rather narrow, with short, small spines. Cephalic process (lateral process, sensu Rodríguez & Hobbs 1989) bifid, with two distinct spiniform teeth apically, both pointing cephalad.

REMARKS

The current geographic distribution of Po. magnus ranges from Mexico to Costa Rica, but some authors ( Rodríguez 1982; Villalobos Hiriart & Álvarez 2008) observed morphological differences in the populations of this species inhabiting southern Mexico, Guatemala, and El Salvador from those occurring in Costa Rica. However, at least concerning the G1 morphology, the specimen from Lake Atitlán ( Fig. 2E, F) is very much similar to the holotype specimen from Costa Rica illustrated by Magalhães et al. (2015: 331, figs 71, 72), except for the cephalic end of the caudal process, which has a distinct protuberance in the Guatemalan specimen whereas it is angled in the holotype. A more detailed study, including molecular analyses, of this group along its distributional area is needed to clarify this issue. The syntypes of Po. magnus are two males deposited at the USNM (USNM 19048 and 19049) from an unknown locality in Costa Rica. Magalhães et al. (2015) illustrated the G1 of the male USNM 19049 and erroneously considered it as the holotype in the caption of the figures 71 and 72. The holotype of Potamocarcinus guatemalensis Rathbun, 1905 , a junior synonym of Po. magnus , is a male (MNHN-IU-2017-8050 [= MNHN-B5170] ( Fig. 2 A-D) from an unknown locality in Guatemala.