Dilocarcinus septemdentatus (Herbst, 1783)

(Fig. 1 a)

Dilocarcinus septemdentatus — Magalhães 2003: 206 p., fig. 109.

Diagnosis. Carapace: 6 distinctive teeth on each anterolateral border. Abdominal segments III–VI of males fused. Third abdominal segment with slight, smooth margin, without the distinction of a crest among the others abdominal segments. Male pleopod (plp 1) gently curving outwards, distal end extending beyond subterminal spine field, as long as spine field (Fig. 1 a).

Habitat. This species was observed within aquatic vegetation, mainly Eicchornia crassipes, along with other crabs such as D. pagei, Trichodactylus borellianus .

Material examined. Nine males and three females, carapace width 22.5 mm (SD 8.69 mm), FANM N° MFA - ZI 347, Salado River) (Argentina, Santa Fe, Santo Tomé, 31°39'S 60°45'W), without collection date, Collins coll.; two males and one female, FANM N° MFA - ZI 402, Colastiné River (Argentina, Santa Fe, Colastiné Sur, 31°37'S 60°34'W), 8.9.63, Martinez; one male, ML-INALI N° B 7, San Javier River (Argentina, Santa Fe, 29°13’S 59°35’W), 30.11.0 5, Collins coll.; one male, ML-INALI N° B 8, Setúbal lagoon (Argentina, Santa Fe, Rincón, 31°35'S 60°39'W), 1.12.0 5, Collins coll.; one male, ML-INALI N° B 16, Los Amores stream (Argentina, Santa Fe, 28°51’S 59°29’W), 29.11.0 5, Collins coll.; two males and two females ML-INALI N° B 21, Parque del Sur lake (Argentina, Santa Fe, Santa Fe city, 31°39'S 60°42'W), 28.11.0 6, Collins.

Southern locations. Setúbal Lagoon (31°35'S 60°39'W), Colastiné River (31°37'S 60°34'W), Parque del Sur Lake (Santa Fe city) (31°39'S 60°42'W) and Salado River (31°39'S 60°45'W), Paraná River floodplain, Argentina.

New distribution. Paraguay, Brazil and Argentina, Salado River as southern limit (31°39’S, 60°45’W) (Fig. 2 a).