Members of the genus Platydoris are large, conspicuous flat bodied dorid nudibranchs. There had been confusion about the identification of its variably colored species and the placement of some questionable species until the recent publication of Dorgan, Valdes and Gosliner's, Phyllogenetic Systematics of the Genus Platydoris, last summer (see reference below).
Platydoris cinereobranchiata is a species I had always confused with Platydoris formosa . Both species are tan with varying amounts of orange-red blotching on the dorsal surface. The name cinereobranchiata was chosen to draw attention to the color of the gills, which are ash grey in P. cinereobranchiata , and are cream colored in P. formosa . The greatest external difference is the absence of large orange ventral spots and pigmentation of the foot in P. cinereobranchiata . Also noteworthy is the presence of small black spots between the rhinophore in P. formosa , with are absent in P. cinereobranchiata .
Platydoris cinereobranchiata is known from the Philippine Islands, and the Solomons (see Bruce Porters specimen on The Sea Slug Forum ) and also from a specimen recorded as P. tabulata from the Seychelles (Dorgan, et al., 2002).
If you take the time to locate and read Dorgan, et al. you will see that a number of species previously thought to be members of this genus are removed because of anatomical features which suggest they should be assigned to other genera.
K.M. Dorgan, Á. Valdés & T.M. Gosliner. 2002. Phylogenetic systematics of the genus Platydoris (Mollusca, Nudibranchia, Doridoidea) with descriptions of six new species. Zoologica Scripta. 31(3): 271-319.
David W. Behrens
Pacific Coast Nudibranchs
Send Dave mail at firstname.lastname@example.org