10 October 1997 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 1 10(3):388-392. 1997. ayutlaensis, a new species of freshwater (Crustacea: Brachyura: Pseudothelphusidae) from Mexico Fernando Alvarez and Jose Luis Villalobos Coleccion Nacional de Crustaceos, Instituto de Biologfa, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-153, Mexico 04510 D.F., Mexico Abstract.—Pseudothelphusa ayutlaensis, new species, is described from the State of Guerrero, Mexico. The new species is placed in the genus Pseudo- thelphusa based on the presence of a first gonopod with the characteristic broadly rounded mesial process and a well developed subtriangular lateral pro- cess. The unique orientation of the mesial and lateral processes of the first gonopod distinguishes P. ayutlaensis from other species in the genus.

The genus Pseudothelphusa de Saussure, Pseudothelphusa de Saussure, 1857 1857, is one of the most diverse within the Pseudothelphusa ayutlaensis, new species family Pseudothelphusidae Rathbun, 1893, Figs. 1, 2 with 22 species (Alvarez & Villalobos 1996, Alvarez et al. 1996), distributed ex- Holotype.—8, cw 24.3 mm, cl 16.1 mm; clusively in Mexico, and one, P. puntarenas junction of Pinela and Tonala rivers, Mun- Hobbs, 1991, from Costa Rica. The genus icipio de Ayutla de los Libres, Guerrero is distributed along the Pacific slope from (16°52'N, 99°12'W), 18 Dec 1987, coll. J. Sonora to Guerrero, throughout central P. Gallo; CNCR 8715. Mexico, and along the Gulf of Mexico Paratypes.—2 8, cw 23.0, 22.0 mm, cl slope in Veracruz (Rodriguez 1982, Alvarez 15.0, 14.4 mm; same locality, date, and col- 1989). Although species of Pseudothelphu- lector as holotype; CNCR 8715. 2 9, cw sa exhibit a great variety of gonopod mor- 36.3, 28.2 mm, cl 23.5, 18.6 mm; same lo- phologies, all exhibit a broadly rounded cality, date, and collector as holotype; mesial process and subtriangular lateral CNCR 8715. lobe (Rodriguez 1982). In the majority of Description.—Dorsal surface of carapace species of Pseudothelphusa the mesial pro- covered with small papillae (Fig. la). In- ferior frontal border continuous, thick, cess of the first gonopod is oriented proxi- slightly sinuous in dorsal and frontal views, mally, descending from the apex towards extending laterally to form superior margin the base of the gonopod and is reniform in of orbits (Fig. lb). Superior frontal border shape, while the lateral process projects lat- formed by the folding of the carapace with erally. In P. ayutlaensis, new species, the an irregular row of blunt tubercles, divided mesial process is oriented distally, extend- by median groove, inclined towards the ing upwards from the apex; and the lateral center (Fig. lb). Postfrontal lobes present as process is projected cephalically. All the two distinct elevations. Median groove specimens are deposited in the Coleccion deep, extending posteriorly beyond post- Nacional de Crustaceos, Instituto de Biol- frontal lobes. Cervical groove wide and ogfa, Universidad Nacional Autonoma de deep, curved slightly posteriorly, reaching Mexico (CNCR). Carapace width and car- anterolateral margin (Fig. la). Cardiac re- apace length are abbreviated as cw and cl, gion of carapace weakly marked. Antero- and expressed in millimeters. lateral margin between orbit and cervical VOLUME 110, NUMBER 3 389

Fig. 1. Pseudothelphusa ayutlaensis, new species, male holotype: a, dorsal view; b, frontal view; c, ventral view. Carapace width 24.3 mm, length 16.1 mm. 390 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

« g Fig. 2. Pseudothelphusa ayutlaensis, new species, a-e left first gonopod: a, lateral view; b, mesial view; c, cephalic view; d, caudal view; e, apical view; f, left third maxilliped; g, right chela. Scale bars: a-e = 1 mm, f = 5 mm, g = 10 mm. VOLUME 110, NUMBER 3 391 groove with irregularly placed denticles, cies it is roughly triangular and ends in two posterior to cervical groove with uniform sharp tips. In southern Guerrero Pseudo- denticles. Ratio exopod/ischium of third thelphusa ayutlaensis and P. galloi share maxilliped 0.73. Ischium of third maxilli- the same drainage system, 10 km away ped trapezoidal in shape; merus narrower from each other. than ischium (Fig. lc). Right chela the larg- est; fingers not gaping, teeth worn out in Acknowledgments holotype. Both chelae with blunt denticle at base of movable finger. We thank Rolando Mendoza for the First gonopod slender, with twisted drawings and Juan Pablo Gallo for donating sperm channel (Fig. 2a). In caudal view the specimens described in this study. (Fig. 2d) with constriction at two thirds its length below cavity of apex. Marginal su- Literature Cited ture sinuous (Fig. 2b). Marginal process ab- Alvarez, E 1989. Smalleyus tricristatus, new genus, sent from apex of gonopod, except for one new species, and Pseudothelphusa parabelli- ana, new species (Brachyura: Pseudothelphusi- sharp tooth at base of mesial process (Fig. dae) from Los Tuxtlas, Veracruz, Mexico.— 2c). Mesial process rounded, oriented dis- Proceedings of the Biological Society of Wash- tally (Fig. 2b). Lateral process extending in ington 102:45-49. laterocephalic direction, wide proximally, , & J. L. Villalobos. 1990. Pseudothelphusa tapering distally, ending in two sharp tips galloi, a new species of (Crustacea: Brachyura: Pseudothelphusidae) (Fig. 2d). Cavity of apex oval shaped (Fig. from southwestern Mexico.—Proceedings of 2e). Crest of cavity of apex low caudally, the Biological Society of Washington 103: higher cephalically. 103-105. Etymology.—The specific name "ayu- , & . 1994. Two new species and one tlaensis" makes reference to the county, new combination of freshwater from Mexico (Crustacea: Brachyura: Pseudothelphu- Ayutla de Los Libres, in the State of Guer- sidae).—Proceedings of the Biological Society rero where the species is distributed. of Washington 107:729-737. Remarks.—The new species is placed in , & . 1996. Especie nueva de cangrejo the genus Pseudothelphusa based on the de agua dulce del Genero Pseudothelphusa torsion of the sperm channel of the first (Brachyura: Pseudothelphusidae) de Guerrero, Mexico.—Anales del Instituto de Biologia, gonopod, and the presence of a typically Universidad Nacional Autonoma de Mexico, rounded mesial process. Pseudothelphusa Serie Zoologfa 67(2):297-302. ayutlaensis is closest to those species of , , & E. Lira. 1996. . Pp. Pseudothelphusa distributed in western 103-129 in J. Llorente, A. N. Garcia-Aldrete, Mexico that lack a marginal process in the & E. Gonzalez, eds., Biodiversidad, Taxonomia y Biogeograffa de Artropodos de Mexico: Hacia apical region of the gonopod (e.g., P. re- una Sintesis de su Conocimiento. Instituto de chingeri Pretzmann, 1965; P. sonorae Rod- Biologia, Universidad Nacional Autonoma de riguez & Smalley, 1969; and P. galloi Al- Mexico-CONABIO, 660 pp. varez & Villalobos, 1990) and to those spe- Hobbs, H. H., III. 1991. A new pseudothelphusid crab cies in which the marginal process is re- from a cave in southern Costa Rica (Decapoda: Brachyura).—Proceedings of the Biological So- duced to a series of small teeth (e.g., P. ciety of Washington 104:295-298. jouyi Rathbun, 1893; P. lophophallus Rod- Pretzmann, G. 1965. Vorlaufiger Bericht iiber die riguez & Smalley, 1969; and P. nayaritae Familie Pseudothelphusidae.—Anzeiger der Alvarez & Villalobos, 1994). The new spe- Mathematisch-Naturwissen-Schaftlichen Klasse cies also resembles P. galloi in the shape der Osterreichische Akademie der Wissenschaf- ten 179:14-24. of the lateral process of the first gonopod. Rathbun, M. J. 1893. Descriptions of new species of Although this process is oriented differently American freshwater crabs.—Proceedings of in both species (cephalically in P. ayutlaen- the United States National Museum 16:649- sis and laterally in P. galloi), in both spe- 661. 392 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Rodriguez, G. 1982. Les crabes d'eau douce del Instituto de Biologia, Universidad Nacional d'Amerique. Famille des Pseudothelphusi- Autonoma de Mexico 40:69-1 12. dae.—Faune Tropicale 22:1-223. Saussure de, H. 1857. Diagnoses de quelques Crus- , & A. E. Smalley. 1969. Los cangrejos de taces nouveaux des Antilles et du Mexique.— agua dulce de Mexico de la familia Pseudo- Revue et Magazin de Zoologie Pure et Appli- thelphusidae (Crustacea: Brachyura).—Anales quee 9:304-306.