The tail end

When we were conducting a survey in late June, Eric spotted an unusual chiton.  I realized it was a species I hadn't seen before, but it was still familiar because it reminded me of a photo I'd seen in a book.  (That's one of the values of browsing through field guides and other natural history books — it helps you recognize something in the field, even if you've never seen it before.)

We were looking for something else, so we had to continue our surveys, but I took a few quick photos for the record.

 

Chitons have eight plates across their dorsal surface, including a head plate (on the left in the photo above) and a tail plate (on the right).  This species is unusual in that the tail plate is higher than all of the other plates, so it looks like a bump or protrusion at the back end.  I didn't capture this feature very well, but here's another view.  If you scan across all of the plates, you can see how the tail plate (on the right) is raised and rounded:

 

In the next image, you can see the sculpturing on the head plate (on the left).  It has 10 nice radiating riblets with little rounded bumps on top.  [Also note that each of the middle plates has two radiating riblets (also with little bumps) on each side.]

 

Meet Callistochiton palmulatus!  It's the first time we've observed this chiton species.  We're still learning about them, but in general it sounds like they're more common in the southern part of their range.  We are aware of one record from Mendocino County in 1946, but otherwise the observations we've found are from south of San Francisco.

One more view of this intriguing chiton walking away towards the other side of the rock: