Family Sesarmidae Dana, 1851 (Marsh Crabs)

Abstract

Carapace quadrate to subquadrate, moderately thick, dorsal surface relatively flat, regions more or less defined with shallow grooves, no junction between anterolateral and posterolateral margins, lateral margins entire or with one dentation behind exorbital angle; pterygostomian region fully covered with network of short hooked setae. Front broad, strongly deflexed, as broad as posterior margin of carapace or even broader. Orbits well developed, shorter than front, infraorbital margin running towards buccal cavern, eyestalks moderately long. Antennules folded transversely. Antennae with basal segment large, laterally expanded, flagellum short, often excluded from orbital hiatus. Third maxillipeds with broad rhomboidal gap between, mandibles visible when third maxillipeds closed, oblique setose ridge on outer surface of ischium and merus. Chelipeds robust, subequal, merus usually with at least one spine on anterodistal margin, fingers apically spoon-shaped. Walking legs robust, distinctly flattened, usually armed with spines and bristles. Abdomen of males and females with seven freely moving somites. G1 robust, nearly straight, usually with dense setae on apical part; G2 much smaller than G1. Genital opening of males and females sternal.