Sea urchin..?

[Vie]

Need an ID for this creature please.

Photo taken at Shark Fin Reef (Hin Phae) near Island #3, Similan Islands, Thailand.

 

[LeslieH]

You're right, a sea urchin. Looks like a good match for Echinometra mathaei images in guide books. They can wedge themselves into really tight places and also bore holes into reef rock m in which they live.

 

[Vie]

Thank you

Another one (also from the Similans) please, if you don't mind.

 

[LeslieH]

wow, what a beauty! I don't have much on echinoderms so I'll send it on to a couple of colleagues. How deep was it and how big?

 

[Vie]

How deep was it and how big?

Depth was less than 15m. Not sure how big exactly but it was tiny - about 3" (or less) across, iirc.

 

[drbill]

Is it some form of pencil urchin?

 

[LeslieH]

Not your standard pencil urchin. I checked with Gordon Hendler, the curator of echinoderms here. He said it was an Echinothrix - the clear sheaths around the spines and the large anal sac are typical for the genus and some of the species have blunt-tipped spines. Even individuals of species with sharp-pointed spines sometimes have blunt spines.