Groove Burrowing Urchin

Moved to "other" (group) :-)

What an unusual urchin! You've put this spotting in the "fish" category, but sea urchins are actually echinoderms (meaning "spiny skin"), and belong in the "other" category. Out of curiosity, did these skeletons wash up on the beach, or did you find them in the water?

Thank you so much Marta, I saw the pictures of the live ones, that's why I was confused.

Namitha: it is because is the skeleton of the sea urchin. You can see in this link how they look like when alive :-) http://www.snv.jussieu.fr/bmedia/aimar2/PAGES/157.htm

Nice spotting. What amazes me is , where are all the spines?. It looks very much like a sea urchin fossil in my collection.

Nice!