Members of the family Scyllaeidae have always been a challenge for me. In the genus Notobryon for example, Notobryon wardi has been used for species occurring in tropical seas around the world. A paper by Marta Pola, Yolanda Camacho-Garcia and Terry Gosliner has shed light on this group and using molecular data, separated the tropical species group into four species.

Notobyron panamica is described in this paper for specimens occurring in Panama, Costa Rica up to Jalisco, Mexico, where this specimen was photographed. Ali and I called this species Notobryon wardi in Eastern Pacific Nudibranchs. It's good to know that this correction has been made.

Notobyron panamica is obviously named for its occurrence in Panamic Biogeographic Province. Similar in variable coloration to N. wardi (Courtesy of Bill Rudman's Sea Slug Forum), it unfortunately can only be distinguished from the other four species by dissection of the male reproductive system and by molecular analysis. The good news is that Pola and party offer molecular evidence that the Indo-Pacific, South African, and eastern Pacific populations are distinct and we can use their geographical ranges to apply their correct scientific name.

If you insist upon hanging your hat on some external differences - The dorsal processes of the eastern Pacific and Indo-Pacific specimens are larger than the ones from South Africa. N. wardi and N. panamica from the eastern Pacific, the coloration is mostly translucent yellow or brownish to orange. Moreover, the lamellae of the rhinophores are pale brown with iridescent green or blue in the Indo-Pacific species whereas the lamellae and their tips are translucent in N. wardi and N. panamica.

I'm not sure this helps all that much, but now we know who's who.