A large southern chromodorid with a raised mantle lobe behind the gill, which holds the sponge toxin it stores and points it at anything that bites.
To about 13 cm, which makes it one of the largest nudibranchs in Australia. The body is firm and rigid, with a wide mantle rim carrying a distinct lobe on each side and a small horn on the back near the rear end, usually bright red. That horn is the short tail of the name, and it is much less developed than in the tropical members of the genus. The ground colour is pale — cream, pink or orange-brown — with orange spots, and it varies a good deal from place to place.
The tropical species of the genus are separated by the horn: theirs is tall and prominent where this one is short and weakly formed.
It is a sponge feeder and lives on temperate rocky reef, jetty piles and kelp beds, from the intertidal down to several tens of metres.
Two notes. It is endemic to southern Australia — southwestern Western Australia, South Australia, Victoria, Tasmania and southern New South Wales — and it does not occur on the Great Barrier Reef or in tropical Western Australia. And there is an unresolved question over an older name, described in 1804, which might have priority; the type material is too poorly preserved to decide.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
