Lobithelphusa mexicana Rodriguez, 1982

Villalobos-Hiriart, José Luis, Kamanli, Seyit A., Álvarez, Fernando, Garbout, Amin & Clark, Paul F., 2019, Lobithelphusa mexicana Rodriguez, 1982 (Decapoda: Pseudothelphusidae): a reassessment of key characters and systematics, Zootaxa 4586 (1), pp. 151-161 : 153-158

Lobithelphusa mexicana Rodriguez, 1982

( Figs. 1 , 2 )

Lobithelphusa mexicana Rodriguez, 1982: 97 , figs. 62, 63.— Villalobos-Figueroa, 1982: 220.— Villalobos-Hiriart et al. 1993: 283.— Álvarez et al. 1999: 23.— Ng et al., 2008: 175 (in list).— Villalobos-Hiriart & Álvarez, 2008: 248, 296 (in list).— Álvarez & Villalobos, 2016: 253.

Material examined. Holotype, male, cl 42.8 mm, cw 71.2 mm; Playa Vicente (17°37’16.4” N, 92°28’21.6” W; 133 m asl), municipality of Playa Vicente, Veracruz, Mexico, purchase of R. Cuming, NHMUK 1860.23 .

Description. In dorsal view ( Fig. 1a ), carapace transversally oval, widest anteriorly dorsal surface flat, smooth regions faintly indicated, gastric and branchial regions inflated, separated by wide, slightly curved, moderately deep cervical groove, narrowing near anterolateral margin of carapace, reaching it as thin fissure. Frontal region punctate, depressed with respect to carapace surface. Postfrontal lobes distinct, anteriorly marked by depressions, separated by narrow median groove, anteriorly forming V-shaped notch dividing straight superior frontal margin, fading posteriorly. Pair of gastric pits distinct, transversal, angled, close to each other on metagastric region. Lateral margins of carapace serrated, anterior half with sharp granules, posterior half smooth and entire; portion between external orbital tooth and cervical groove straight with low, rounded granules, and in a lower level as rest of the margin. Posterior margin of carapace straight. In frontal view ( Fig. 1b ), front vertically deflexed and smooth; inferior frontal border granulated, more advanced than the superior border, with narrow medial notch; superior frontal border bilobed, lobes defined by a row of granules, separated by median notch, slightly inclined towards median groove. Superior margin of orbit formed by granules, continuous with inferior frontal border; lower orbital margin marked by row of granules; exorbital angle projected, narrow, acute; internal border of orbit moderately high; orbital hiatus occupied by basal article of antenna. Median septum that divides antennular fossae thin, visible. Epistomal margin with median triangular tooth, tip acutely rounded, separated from lateral teeth on either side by wide notch with granulate borders. Orifice of efferent branchial channels open, with gap between jugal and lateral angles. Pterygostomial area glabrous, faintly granulated ( Fig. 1 b–d).

First pereiopods distinctly heterochelous, robust, left cheliped larger than right. Left cheliped with merus subtriangular in cross section; inner and outer borders rounded, granulated; lower surface smooth; upper border armed with alternate small and large triangular spines; upper internal angle as a rounded plate whose edge has low teeth. Carpus surface smooth, superior border armed with row of five conical tubercles, two proximal smaller; internal angle with prominent conical spine. Palm moderately swollen, smooth. Fingers punctate, slightly curved inward, gaping, tips crossing, bearing triangular sharp teeth on cutting edges; dactyl slender, tip abruptly curved downwards, with longitudinal rows of low, rounded granules on dorsal surface; cutting edge with two large proximal teeth, rest decreasing in size distally. Propodus slightly more robust, punctate, cutting edge with three proximal teeth small, rounded, the following two very strong, markedly swollen externally, rest triangular decreasing in size distally, tip stout, moderately upwards, and rounded ( Fig. 1e, f ). Right cheliped moderately slender; merus internal surface smooth, superior border tuberculate, inferior one granulated; palm smooth, inferior surface delicately granulated; chela with the fingers curved inwards, closing completely, cutting edges armed with triangular teeth, tips crossing; dactyl with dorsal surface granulated; cutting edge of propodus with alternate large and small sized teeth ( Fig. 1 a–d).

Ambulatory pereiopods normal, decreasing in length posteriorly; ischia and meri smooth; carpi and propodi with rugose surface; dactyli bearing 4 or 5 longitudinal rows of small, sharp, corneous spinules; length variable from equal to longer than propodus ( Fig. 1a, d ).

Ventral surface smooth, sternal sutures discernible; first and second sternites triangular, third to fourth partially fused, fifth to eight well marked ( Fig. 1d ). Abdomen triangular, all somites free, third somite broadest, sixth longer. Telson triangular, proximal margin slightly sinuous, lateral margins straight, apex rounded ( Fig. 1d ).

Male first gonopod description as in diagnosis of genus.

Figures

FIGURE 1. Lobithelphusa mexicana, male holotype, NHMUK 1860.23. Carapace: dorsal surface, a; frontal portion, b; lateroventral surface, c; ventral surface, d. Larger chela: internal surface, e; external surface, f.

FIGURE 2. Lobithelphusa mexicana, male holotype, NHMUK 1860.23. First gonopod, a–d: mesial view, a; lateral view, b; cephalic view, c; caudal view, d. Abbreviations: ac, apical cavity; an, apical notch; lc, lateral crest; lex, lateral expansion; lsp, lateral spines; lsh, lateral shoulder; mdl, mesial distal lobe; mpl, marginal plate; mssp, mesial subdistal spine; og, oval gap; vgr, vertical groove.