Length to 38 mm (females, Oxycephalus clausi 1), to 27 mm (males). Females dimorphic, as in Oxycephalus piscator, but not as strong as in that species. Head of small form with more convex ventral and dorsal margins, triangular rostrum twice as short as whole head, with clear border between it and main part of head on ventral margin. Head of large form only slightly convex dorsally, triangular rostrum 3 times as short as whole head, without clear border between it and main part of head. Males with same general appearance as large females, but with head slightly more elongate. Head of large females moderately shorter than in Oxycephalus piscator, subequal only to pereonites I-V combined. P I with broadened ART 2 shorter than distal ART combined; ART 5 with denticle on anterior margin, slightly convex posterior margin, posterodistal process sharp, broadly triangular, with strongly serrate inner, finely serrate outer margins, subequal to ART 6, which is broadly suboval and with straight posterior margin. P II larger than P I (Oxycephalus clausi 2), ART 2 broadened, shorter than distal ART combined; ART 5 with denticle on anterior margin, convex posterior margin, narrowly triangular, sharp, posterodistal process curved apically, longer than oval ART 6, possibly reaching top of dactyl; inner margins of chela dentate, denticles on ART 5 and 6 fit each other snugly. Chela of P I and II with fine setae. ART 2 of P V-VI very broad, with strongly concave distal margin. Epimeral plates each with 2 denticles (in centre of distal margin and on posterodistal corner). Telson serrate in distal part.