Ostracotheres, H. Milne Edwards, 1853

Ahyong, Shane T. & Mendoza, Jose Christopher E., 2024, Confirmation of Ostracotheres H. Milne Edwards, 1853 from Southeast Asia in a new species from Singapore and Indonesia (Crustacea: Decapoda: Brachyura), Zootaxa 5476 (1), pp. 9-16 : 14-15

Key to species of Ostracotheres

1. Pereopods 2–5 dactyli stout, falcate, apices distinctly curved, some turning almost perpendicular to main axis. Pereopod 5 dactylus shorter than propodus. Maxilliped 3 exopod flagellum 2-segmented. In tridacnine clams. [Red Sea and western Gulf of Aden]...................................................................... O. tridacnae ( Rüppell, 1830)

– Pereopods 2–4 dactyli slender, gently curved, apices weakly curved, to less the 45° to main axis. Pereopod 5 dactylus relatively straight, as long as or longer than propodus. Maxilliped 3 exopod flagellum unsegmented. In ascidians................. 2

2. Buccal margin of epistome with small triangular median projection. Pereopods 2–4 dactylus flexor margin lined with corneous spinules for no more than proximal two-thirds. Longest walking leg (pereopod 3) about 1.1 × cl in females. [Red Sea and western Gulf of Aden].............................................................. O. cynthiae Nobili, 1906

– Buccal margin of epistome straight, without triangular median projection. Pereopods 2–4 dactylus flexor margin lined with corneous spinules for about proximal three-fourths. Longest walking leg (pereopod 3) about 1.5 × cl in females. [Southeast Asia]............................................................................... O. caramica sp. nov.