Sylvathelphusa, Villalobos, José Luis & Álvarez, Fernando, 2013

Villalobos, José Luis & Álvarez, Fernando, 2013, Two new genera and three new species of freshwater crabs (Crustacea: Pseudothelphusidae: Potamocarcinini) from Chiapas, Mexico, Zootaxa 3599 (5), pp. 457-470 : 459

Sylvathelphusa n. gen.

Diagnosis. Carapace with flat dorsal surface, regions distinct, median groove shallow. Merus of third maxilliped with external margin broadly rounded, shallow notch on anterior margin rounded; ischium trapezoidal, becoming broader distally, ratio exopod/ischium 0.5. Male first gonopod latero-mesially compressed, slightly arched in caudal and cephalic views, of same thickness along its length; distal processes well developed. In mesial view, marginal suture straight along most of gonopod, slightly concave in the middle. Marginal plate between caudal and mesial surfaces abruptly widening distally, forming triangular or rectangular apical projection overreaching cephalic spine, lying on caudal margin of mesial surface, ending in acute distal margin. Mesial surface ending distally in tongue-like apical projection, disto-cephalically directed, longer than apical projection of marginal plate, distal margin broad, rounded, sculptured with shallow longitudinal grooves and scattered subacute granules or thin and divided with acute and robust spines. Mesial process as triangular spine, stout and acute, cephalad or laterally directed, forming 90º angle with respect to principal axis of gonopod. Lateral suture visible through proximal twothirds, separating marginal plate from caudal surface. In cephalic view, mesial process conical, stout and acute. Lateral surface with 1 or 2 small, triangular, distomedial tubercles; distal third of laterocaudal portion, forming a high border, rounded, with a mid-triangular and low prominence or a distocaudal spine, strong, conical and acute. Apical projection of mesial surface, tongue-like, with rounded, broad, granulated margin or armed with acute spines. In lateral view, caudal margin with wide and shallow or deep and narrow lateral notch, located at midlength. Lateral surface widening caudally in distal third into a semirounded plate, with 1 or 2 small triangular, distomedial tubercles, caudal border high, laterally directed with triangular and low prominence or distocaudal spine. Deep suture in the base of apical projection of mesial surface, marking separation of lateral and mesial plates. In caudal view, gonopod slightly arched laterally. Distal half with lateral margin expanded, armed with triangular prominence or acute and conical spine. In apical view, apical projection of marginal plate ending in acute tip or thin border armed with spines. Apical projection of mesial surface broad and rounded, with acute tubercles or thin and divided with acute, robust spines. Apical cavity covered by hood formed by crest of lateral plate or open surrounded by crests of mesial and lateral surfaces. Caudal border of lateral surface ending distally in triangular prominence or in acute, conical, strong spine. Opening of spermatic channel at the base of apical projection of mesial surface.

Type species. Sylvathelphusa kalebi n. sp.

Other species included. Sylvathelphusa cavernicola n. sp.

Etymology. The generic name is derived from the Latin sylva (forest) and Thelphusa , the generic name for freshwater crabs.

Distribution. Southern and central portions of Chiapas, Mexico.

Remarks. Based on the morphology of the male gonopod, Sylvathelphusa n. gen. belongs in the tribe Potamocarcinini and is closely related to Potamocarcinus . A conical mesial process, with a stout and acute spine, cephalad or laterad directed, forming a 90º angle with respect to the principal axis of the gonopod, and a marginal plate placed between the caudal and mesial surfaces, and overreaching the cephalic spine, are traits found in the species of both genera. The gonopod morphology of Potamocarcinus and Sylvathelphusa n. gen. differ, however, in the form, ornamentation and position of the apical projections of the marginal and mesial plates, in the cover of the apical cavity by the apical crests, and in the position of the aperture of the spermatic channel.