Mystery slug from Cannon Beach, Oregon

January 12, 2007
From: Minette Layne

Dear Sea Slug Forum,

I saw this nudibranch in a tide pool this summer while at Cannon Beach, Oregon, USA, and am having a difficult time identifying it.

I thought perhaps it was Dendronotus frondosus, but felt uncertain about that because it doesn't look the same (to me) as the photographs of D. frondosus I found on the forum. The rhinophores, in particular, seem a bit different from what I'm seeing in the other pictures.

I know the picture quality is poor and so this might remain a mystery forever. But I'd be most grateful if someone can help me identify this critter.

Locality: Cannon Beach, In a tide pool, Oregon, USA, Pacific Ocean, April 29, 2006, Intertidal. Length: 1/2 inch. Photographer: Minette Layne.

All the best,
Minette Layne
Seattle, Washington, USA

Layne, M.C., 2007 (Jan 12) Mystery slug from Cannon Beach, Oregon. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Hi Minette:
This critter is pretty rare.  It is Dendronotus subramosus.  The rhinophoral crown papillae are what I use to ID this species, which can be easily confused with both Dendronotus frondosus and Hancockia californica (the latter is a more southern species).  Note that in your specimen, the papillae on the rhinophoral crown are short and blunt, and there are no lateral rhinophoral processes.  In D. frondosus the crown papillae are branched.  In both the color varies widely.

Hope this helps.

Behrens, D.W., 2007 (Jan 12). Comment on Mystery slug from Cannon Beach, Oregon by Minette Layne. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Dendronotus subramosus at work
    From: Jan Kocian, June 4, 2007
  2. Dendronotus subramosus from Monterey, California
    From: Clinton Bauder, January 27, 2006
  3. Dendronotus subramosus - Take 2
    From: Clinton Bauder, September 15, 2005
  4. Dendronotus subramosus? from California
    From: Sean Kearney, March 23, 2004
  5. Mystery slug is Dendronotus subramosus
    From: Dave Behrens, August 9, 2003
  6. Unknown nudibranchs from California
    From: Bruce Wight, December 7, 2001
  7. Nudibranch from British Columbia
    From: Andy Murch, July 8, 2001

Show factsheet and all related messages