Heterotrophic dinoflagellate (Gyrodinium pellucidum?)

Dear

This dinoflagellate was in the plankton sample from today. When trying to identify it later on, I couldnt find any similar species.
One possible organism could be Gyrodinium pellucidum (in Dodge, Marine Dinoflagellates of the British Isles, fig 11 j). But the sulcus is not as broad as in the Dodge and neither fits well to the occurence in the Pacific and Barents Sea.

The Danish planktonbook (Plankton i de indre danske farvande) also have some similar Gymnodinium in. ed. sp 2. (Fig 4.37 v). They also note that such dinos can be sexual stages to larger ones.

Any ideas?

The picture can be viewd at
https://picasaweb.google.com/111165327260999307595/PicturesOfPlanktonFro...

Best regards
Fredrik