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I found this item on the beach today in north west England. It’s very light weight and delicate, about 3cm long and some interesting patterns on it. Any ideas on what it is would be greatly appreciated

photo showing seams almost like a baseball

photo showing small bumps in patterns

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This is almost certainly the shell of a Sea Urchin. These are spiny echinoderms that are found almost world-wide in many different species in the littoral down to ~5000 m (16,404 feet) depth. They have five-fold symmetry, meaning the shell is divided into 5 parts that are more or less symmetrical, like a five-pointed star.

The reasons I say this is so, is that the shell (called a "test") is hollow, it is covered in small protrusions that are the remains of the spines. You can also see some of the smaller spines in the top picture at the edges of the bottom two seams in the shell, and you can see the symmetry in the top picture. You can see a sea-urchin shell with the spines removed, in a bit better state than your one, at the bottom of this page from Arizona State University

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  • $\begingroup$ I knew it was an echinoderm, but didn't think of a sea urchin, as I've seen a bunch of different ones, but never this. Is it a heart urchin/sea potato (here and here)? I've never seen those. $\endgroup$ Jan 27 at 23:32
  • $\begingroup$ @anongoodnurse No idea on the species at all. Chances are it's one of the common ones. Having had a quick look for "heart urchin test" it could well be a heart urchin - it's definitely an asymmetric test, so something along those lines is probably right. $\endgroup$
    – bob1
    Jan 28 at 4:05
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This is a Sea Potato (Echinocardium cordatum).

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    $\begingroup$ Welcome to the Biology Stack Niels. Please take a tour and visit the help center for more information on how this particular Stack works. Your answer looks like a good start for an answer as we value answers that provide a bit more than the basics - reasons why you think it is E. cordatum and some references/links to back it up would help. $\endgroup$
    – bob1
    Jan 28 at 19:58

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