Phyllidiella cooraburrama? from Papua New Guinea

Dear Richard,
Thanks for this photo. It sent me back to Des Paroz's messages [message 1, message 2], where I suggested his animal might be Phyllidiella cooraburrama. I also note that Neville Coleman's 1001 Nudibranchs has this identified as Phyllidiella nigra. Identifying phyllidiids just from photos is a bit risky as often the essential characters are on the underside of the animal or in fact inside it. Also, we know so little about colour variation in most species, that deciding whether colour differences mean different species is not a very 'scientific' exercise.

Both P. nigra and P. cooraburrama are good guesses for this species but in Brunckhorst's monograph he specifically states that neither of these species has a 'pale edge to the mantle' and yet your photo clearly shows a continuous pinkish edge. There is a third species which fits this colour and tubercle pattern quite well and that is Phyllidiopsis burni. Brunckhorst specifically describes 'edge of mantle is very thin, smooth and translucent pink'. He also also states that the body is 'more acutely tapered than other phyllidiids'. Although this is difficult to quantify, your animal is quite pointed at each end.

I think your animal is Phyllidiopsis burni. And I suspect Des Paroz's is as well. You mention you may have placed the animal on the coral for a better shot. I had wondered why it was holding its foot up off the coral. Although the stinging nematocysts in Porites are considered not very nasty, nudibranchs often find them very uncomfortable to move over, especially if they haven't been able to lay down a layer of mucus to slide over.
Best wishes,
Bill Rudman