Pseudothelphusa hermosorum, Madrigal & Villalobos-Hiriart & Álvarez, 2025

Madrigal, Kevin J., Villalobos-Hiriart, José Luis & Álvarez, Fernando, 2025, Integrative taxonomic analysis of the Pseudothelphusa americana de Saussure, 1857 species complex with the description of three new species (Decapoda, Pseudothelphusidae, Pseudothelphusinae), Zootaxa 5659 (1), pp. 1-28 : 17-19

Pseudothelphusa hermosorum sp. nov.

http://zoobank.org/ 76ED3203-4225-4E3B-8DF7-B84C22F7EF76

( Figures. 6 , 8 )

Pseudothelphusa americana – Villalobos-Hiriart 2005: 137, 219 (key), 230, 232, 333, table 6, pl. XIV [not Pseudothelphusa americana de Saussure, 1857 ].

Type material examined. Holotype (herein designated): male (CL 24.32 mm, CW 37.39 mm) ( CNCR 36592 ), underground water channel, used for water supply to town San Marcos Necoxtla, municipality of Tehuacán , Puebla, 18°24’37.44“N 97°22’5.16“W, coll. K.J. Madrigal, E.F. Huerta, M. Hermoso & A. Estradas, 31 July 2022 . Paratypes: 2 males (CL 17.72–17.92 mm, CW 26.34–27.05 mm), 2 females (CL 20.69–22.94 mm, CW 31.30–35.89 mm) ( CNCR 36593 ), same data as holotype .

Other material examined. 3 males (CL 19.85–21.47 mm, CW 29.82–32.33 mm), 2 females (CL 16.38–19.54 mm, CW 23.8–29.72 mm) ( CNCR 36591 ), same locality as holotype, coll. E.F. Huerta, M. Hermoso & L. Hermoso, 24 June 2022 .

Description. Carapace slightly convex; surface finely punctuated, reticulated, punctuation denser near frontal border ( Fig 6B ). Superior frontal border absent; front gently curved downwards; frontal border bilobed, continuous, thick, lightly punctuated, giving it crenated appearance, central portion with shallow depression ( Fig 6A, B ). Postfrontal lobes barely distinguishable; frontal median groove poorly defined, wide; cervical grooves well marked, straight, deeper anteriorly, not reaching anterolateral margin ( Fig 6B ). Gastric region well defined, convex, slightly higher than branchial region; cardiac region marked by 4 deep depressions, 2 near urogastric area, 2 close to gastric region; urogastric sutures Y-shaped, slender, horizontally disposed, straight in middle ( Fig 6B ). External orbital angle without notch ( Fig 6B ). Anterolateral margin lightly granulated, granules inconspicuous, widening towards orbital external angle; posterior margin straight ( Fig 6B ).

Frontal border straight in frontal view, convex at level of antennal fossae, with conspicuous widening at lateral angle ( Fig 6A ). Orbits subquadrangular; margin completely crenated; inferior margin slightly inclined; external angle rounded; internal tooth subtriangular, as grooved plate, extends until meeting lateral angle of frontal border, closing the orbital hiatius ( Fig 6A ). Antennae not separated from front; antennal basal article partially covered by widening of lateral angle ( Fig 6A ). Interantennular septum small, blunt, not visible, inserted under frontal border. Operculum of antennal gland ovoid, with tuft of bristles on external portion. Efferent branchial channel aperture subquadrangular, width/length ratio 1.13. Epistomal tooth at septum level, triangular, downwards directed. Pterygostomial region and epistome pubescent. Third maxillipeds covering buccal cavity; ischium subtrapezoidal, width/length ratio 0.84, gnathal margin with small subquadrangular teeth decreasing in size distally, long bristle tufts in between teeth; merus with anterolateral border rounded, not extending beyond buccal cavity, width/length ratio 1.2, anterior notch well defined; gnathal border gently excavated to permit palp insertion, inferior portion with small teeth, long bristles; palp mesially pubescent, decreasing in thickness towards dactylus; third maxilliped surface punctuated, each punctuation with setae, distributed along gnathal margin; exognath wide, short, ending in rounded apex, exognath/ischium length ratio 0.56 ( Fig. 6C ).

Chelipeds asymmetrical. Merus internal border with small tubercles; carpus with internal border granulated, small, wide granules; distal portion with triangular spine, wide, with acute apex. Major chela with palm surface punctuated; fingers separated by broad gap; dactylus slender, curved; cutting borders with well-developed triangular teeth ( Fig 6D ).

G1 strong, distal third twisted towards median axis of sternal surface of body. In caudal view, distal third straight; distal crest of caudo-marginal projection higher than lateral crest; distal end of caudal surface with shallow concavity ( Fig 6G ). Caudal surface of mesial process with basal lobe poorly developed, barely noticeable. In mesial view, caudo-marginal projection with subapical surface of caudal margin slightly concave; crest of distal lobe smooth, widely rounded caudally, straight cephalically; distal lobe small, with acute apex, tip with fine spine, acute, inconspicuous, separated from proximal lobe by narrow V-shaped notch; proximal lobe U-shaped, short, broad, length/width ratio 1.11, oblique to principal axis, with widened, rounded apex ( Fig 6H ). In cephalic view, distal third slightly inclined laterally, distal and proximal lobes of caudo-marginal projection disposed in same plane; short carina on inner face of proximal lobe, reaching one third of its surface, notably widened ( Fig 6F ). Mesial process subtriangular, perpendicular to G1 principal axis, ending laterally in triangular spine with subacute apex; superior border with straight, long crest, reaching inner lobe, middle portion elevated; inferior border gently curved; inner lobe widely triangular, with slightly rounded borders, wide, separated from inner surface of proximal lobe ( Fig 6F ). In lateral view, mesial process caudally projected; basal lobe of caudal surface inconspicuous ( Fig 6I ). In distal view, apical cavity wide U-shaped; central crest high, straight narrow; apical spine field deep, arranged in central stripe with approximately 17 long spines, cephalic spines partially covered by superior border of mesial process ( Fig 6E ). Aperture of spermatic channel in caudal position, wide. Mesial process short, lateral spine faintly widened proximally, straight, laterally directed ( Fig 6E ).

Type locality. Underground water channel used for water supply in town San Marcos Necoxtla (18°24’37.44”N 97°22’05.16”W), Tehuacán , Puebla, Mexico .

Etymology. This species is dedicated to the Hermoso siblings, Ana Margarita, Luis and José who notified us about the existence of a Pseudothelphusa population in San Marcos Necoxtla, and helped us find the necessary crabs to carry out the analysis. The specific epithet is formed by using as root the last name ‘Hermoso’ and adding to the suffix ‘-orum’.

Remarks. This species presents clear differences when compared to P. americana s. s. Pseudothephusa hermosorum sp. nov. shows lateral thickenings of the frontal border ( Fig. 6A ) (versus no lateral thickenings, and a more slender frontal border in P. americana s. s.; Fig. 4A ); the exognath length/ischium length ratio in P. hermosorum sp. nov. is 0. 65 ( Fig. 6C ) (versus 0.83 in P. americana s. s.; Fig. 4C ). The caudo-marginal projection of the male G1 is notably different between the two species. The proximal lobe in P. hermosorum sp. nov. is oblique, short and broad, and with a length/width ratio of 1.11 ( Fig. 6H ) (versus parallel to the principal axis, elongated, and with a length/width ratio of 1.85 in P. americana s. s.; Fig. 4H ). Additionally, the number of spines in the apical cavity is less in P. hermosorum sp. nov. (17) ( Fig. 6E ) than in P. americana s. s. (21) ( Fig. 4E ). Villalobos-Hiriart (2005) considered P. hermosorum sp. nov. as the Tehuacán form of P. americana s. s. and offered a formal description. In the present survey, molecular, morpho-geometric, and morphological evidence support the description of a new species.

One ovigerous female of the new species was examined. The female (CL 20.69 mm, CW 31.3 mm) was carrying 79 eggs, each with a diameter of 2.12–2.35 mm.

Distribution. Pseudothelphusa hermosorum sp. nov. has only been collected in the type locality.

Figures

FIGURE 4. Pseudothelphusa americana sensu stricto, male, neotype (CL 26.60 mm, CW 40.63 mm) (CNCR 35390).A, frontal view; B, dorsal view; C, ventral view; D, major chela; E, G1 distal view; F, G1 cephalic view; G, G1 caudal view; H, G1 mesial view; I, G1 lateral view. Abbreviations: ASF, apical spine field; BL, basal lobe; DC, distal crest; DL, distal lobe; LC, lateral crest; MP, mesial process; PL, proximal lobe; SCA, spermatic channel aperture. Scale bars: A–D = 5 mm; E–I = 1 mm.

FIGURE 6. Pseudothelphusa hermosorum sp. nov., holotype (CL 24.32 mm, CW 37.39 mm) (CNCR 36592). A, frontal view; B, dorsal view; C, ventral view; D, major chela; E, G1 distal view; F, G1 cephalic view; G, G1 caudal view; H, G1 mesial view; I, G1 lateral view. Abbreviations: ASF, apical spine field; BL, basal lobe; DC, distal crest; DL, distal lobe; LC, lateral crest; MP, mesial process; PL, proximal lobe; SCA, spermatic channel aperture. Scale bars: A–D = 5 mm; E–I = 1 mm.

FIGURE 8. Map of central Mexico showing the distributions of the four Pseudothelphusa species recognized in this study. Localities: 1, Mixquiahuala; 2, Ventoquipa; 3, Michac; 4, Chignahuapan; 5, Zacatlán de las Manzanas; 6, San Miguel La Presa, Ixtacuixtla; 7, La Ascención Huitzcolotepec; 8, ‘El Ojito’ Spring, Apizaco (P. americana s. s. type locality); 9, Palo Huérfano; 10, Cuahutinchán; 11, Cuauxixtla; 12, San Marcos Necoxtla; 13, Ajolotero River, near Chilapa; 14, Querétaro-state of Mexico. State abbreviations: CMX, Mexico City; GUA, Guanajuato; GRO, Guerrero; HID, Hidalgo; MEX, State of Mexico; MIC, Michoacán; MOR, Morelia; OAX, Oaxaca; PUE, Puebla; QUE, Querétaro; TLA, Tlaxcala; VER, Veracruz.