The Cymonomidae of the Philippines (crustacea: Decapoda: Brachyura), with Descriptions of Four New Species

The deep-sea crabs of the family Cymonomidae collected by the PANGLAO 2004, PANGLAO 2005 and AURORA expeditions are reported. Five species of Cymonomus A. Milne-Edwards, 1880, are reported of which four are new to science: C. diogenes, C. deforgesi, C. gracilipes, and C. mariveneae. Cymonomus hakuhoae Takeda & Moosa, 1991, previously known only from a single damaged specimen from Indonesia. was rediscovered in the Philippines, and is redescribed here based on specimens of both sexes. This increases the number of cymonomids known from the Indo-West Pacific from 16 to 20. Members of Cymonomus have abdominal somite 6 and the telson fused without trace of a suture separating them; this is the primary character that distinguishes Cymonomus from members of Cymonomoides Tavares, 1993, in which the two are separated by a visible suture. The specimens and species on hand suggest that this character may not be reliable. Our observations of Cymonomus diogenes, new species, and a very similar species, Cymonomoides delli (Griffin & Brown, 1976), from Australia, indicate that both are best placed in Cymonomus sensu stricto and that other putative species of Cymonomoides require restudy. Sexual dimorphism is confirmed in lengths of the second and third pereopods in the three species of Cymonomus for which both sexes were collected in addition to C kapala from Australia. Cymonomids are rarely collected and usually known only from few specimens and often a single sex (generally female). Further sampling will probably show sexual dimorphism in ambulatory leg length to be a general pattern in the family.