Xoconochcothelphusa, Villalobos-Hiriart & Moreno-Juárez & Álvarez, 2024

Villalobos-Hiriart, José Luis, Moreno-Juárez, Eric G. & Álvarez, Fernando, 2024, Xoconochcothelphusa, a new genus for Ehecatusa chiapensis (Rodríguez & Smalley, 1972), with notes on Spirothelphusa Pretzmann, 1965 (Crustacea: Decapoda: Pseudothelphusidae), Zootaxa 5523 (2), pp. 171-191 : 179-181

Xoconochcothelphusa n. gen.

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Diagnosis. Carapace with dorsal surface flat, smooth; cervical and mid frontal grooves deep, well marked; frontal portion vertical, superior border present, ornamented with blunt granules; lateral margin slender, serrated with acute granules. Orbits with small, triangular, internal tooth, on inferior portion; orbital hiatus open ( Fig. 4 ). Exopod of third maxilliped subequal in length to lateral border of ischium (0.9 × its length). G1 straight, stout, without lateral lobes or crenate border on mid length of principal axis, distal third twisted towards median axis of sternal surface of body. In mesial view, marginal plate and caudal surface fused distally to caudo-marginal projection, ending apically in broad subrectangular distal lobe (1.6 × as wide as long), cephalad directed, superior border straight, inferior one undulated ending in subterminal triangular tooth ( Fig. 5A ). Apical cavity concealed by distal lobe of caudo-marginal projection, narrowly opened, in transversal position. Apical portion of mesial surface with three prominent triangular teeth, similar in size, cephalad directed, proximal one being mesial process, two distal ones constituting lateral process, both extending beyond apical cavity of gonopod. In total view, principal gonopod axis straight, surface smooth; marginal suture well marked through proximal 2/3 of its length, with row of long setae on proximal portion ( Fig. 6A ). In cephalic view, apical portion with three prominent teeth, distal one somewhat rounded, medial and proximal ones triangular, similar in size, cephalad directed, ending in subacute tip ( Fig. 5B ). Apical cavity and setal field partially visible. Distal lobe of caudo-marginal projection broad, inferior border and subterminal triangular tooth discernible. Lateral shoulder evident, rounded. In total view, principal gonopod axis straight along mesial surface; lateral surface sinuous, with subdistal rounded prominence, constrained at middle length, straight proximally, slightly widening at base ( Fig. 6B ). In lateral view, lateral surface ending distally in well-marked lateral shoulder, forming 90º angle having vertex widely rounded. Distal crest of caudal surface forming part of apical cavity ( Fig. 5C ). Apical portion with three prominent triangular teeth fused at base, cephalad directed, distal one shorter, basal portion subrectangular, superior margin moderately rounded; median and proximal ones similar in size, triangular. In total view, principal gonopod axis with cephalic surface flat, almost straight; lateral surface ending in subdistal shoulder, caudal surface with subdistal widely rounded prominence, proximally constrained at distal third and ending in small notch, extending slightly curved to base of G1 ( Fig. 6C ). In caudal view, distal crest sharp, mesocaudally projected forming caudal portion of apical cavity; distal lobe of lateral process flat, overreaching distal crest of caudal surface; median lobe triangular; lateral shoulder rounded ( Fig. 5D ). In total view, principal gonopod axis with marginal plate discernible, fringe of setae on proximal third of marginal suture, lateral surface ending in subdistal rounded prominence, continued proximally as wide concavity at base of G1 ( Fig. 6D ). In distal view, apical cavity slit like, slender, transversal relative to principal axis of gonopod, delimited by distal crest of caudal surface, distal border of lobe of caudo-marginal projection and lateral process; central crest as irregular plate in center of apical cavity; setae field subapical, with scarce apical setae, some extending to medial lobe of lateral process; opening of spermatic channel irregular shape, in caudal position ( Fig. 5E ). Prominences of lateral process evident, distal lobe rounded, margins curved, reaching well beyond apical cavity; median one as half circle, external border rounded, internal one straight, with sparse setae extending proximally. Lateral shoulder perceptible, margin rounded.

Type species. Xoconochcothelphusa chiapensis n. comb., designated herein.

Species included. Xoconochcothelphusa chiapensis ( Rodríguez & Smalley, 1972) , n. comb.

Etymology. The name of the new genus comes from the Nahuatl “Xoconochco” (= Soconusco), which is the regional designation for the Pacific slope of Chiapas state, the region of the Xoconochtli (nochtli—Prickly pear or pear cactus, xocotl—Fruit, xococ—Sour), that is the place where the sour fruit of the prickly pear grows.

Distribution. The genus is so far known to be endemic to the state of Chiapas, Mexico.

Remarks. The concatenated tree obtained from a multigene analysis based on partial DNA sequences of mitochondrial and nuclear genes (COI, 16S and H3) recovered Xoconochcothelphusa chiapensis n. comb. and Ehecatusa mixtepensis as independent branches within the subfamily Pseudothelphusinae . The new position of X. chiapensis is supported by the presence of the caudo-marginal projection, a diagnostic character of the subfamily ( Villalobos & Álvarez 2010; Álvarez et al. 2020). Morphological differences between Ehecatusa and the new genus Xoconochcothelphusa are described in the taxonomic section.

Based on the morphology of the G1, the relationships of the new genus with the rest of the known genera of Pseudothelphusinae are hard to establish. Nevertheless, it can be assigned to the subfamily by the distal fusion of the marginal plate with the caudal surface, to form a caudo-marginal projection that ends distally in a transversal broad, subrectangular plate, cephalad directed, with the superior border straight and the inferior one undulated. The characteristics that distinguish Xoconochcothelphusa n. gen., from other genera in the subfamily Pseudothelphusinae are: 1) the shape of the caudo-marginal projection and 2) the fusion of the mesial and lateral processes forming an apical portion of the principal axis with three triangular teeth, like a trident, prominent, similar in size, cephalad directed, and distally surpassing the apical cavity.

Figures

FIGURE 4. Xoconochcothelpusa chiapensis (Rodríguez & Smalley, 1972) n. comb., male holotype (cl 15.3 mm, cw 26.5 mm) (CNCR 310). A, carapace, dorsal view; B carapace, frontal view; C, major chela.

FIGURE 5. Xoconochcothelphusa chiapensis (Rodríguez & Smalley, 1972) n. comb., male holotype (cl 15.3 mm, cw 26.5 mm) (CNCR 310), distal portion of left G1. A, mesial view; B, cephalic view; C, lateral view; D, caudal view; E, distal view. Abbreviations: Ac = apical cavity; Ccac = central crest apical cavity; Cmp = caudo-marginal projection; Cs = caudal surface; Dccs = distal crest of caudal surface; Dlcmp = distal lobe of caudo-marginal projection; Lp = lateral process; Lsh = lateral shoulder; Map = marginal plate; Mas = marginal suture; Mep = mesial process; Sf = spine field of apical cavity; Spch = spermatic channel.

FIGURE 6. Xoconochcothelphusa chiapensis (Rodríguez & Smalley, 1972) n. comb., male holotype (cl 15.3 mm, cw 26.5 mm) (CNCR 310), total view of left G1. A, mesial view; B, cephalic view; C, lateral view; D, caudal view. Abbreviations: Fsmap = fringe setae marginal plate; Las = lateral suture; Map = marginal plate; Mas = marginal suture.