Common British sea urchin: The empty test or shell of the Heart Urchin commonly known as the Sea Potato, Echinocardium cordatum (Pennant), from Whiteford Sands strandline, Gower, South Wales. Under surface with spines still attached (1)

A seashore favourite of mine is the Heart Urchin, also known as a Sea Potato, Echinocardium cordatum (Pennant). Here is one from the strandline at Whiteford Sands, Gower, South Wales. This photograph shows the under surface of the empty test or shell of the animal with the spines still attached.

The photograph below shows the upper surface of the sea urchin test – again with the spines still attached but you will notice that the individual spines are a different shape from the ones on the lower surface.

Dead Heart Urchin with spines attached: Heart Urchin known as Sea Potato, Echinocardium cordatum (Pennant), empty test, upper surface, spines still attached, from Rhossili Bay, Gower, South Wales, U.K. (2)

The spines easily fall off after the sea urchin dies because they are held in place by the skin which rapidly disintegrates. The picture below (taken on Rhossili beach) shows the upper surface of the empty test without any spines. You can see the pattern of tubercles with which the spines articulated.

"Sea Potato" sea urchin test without spines: The Heart Urchin known as a Sea Potato, Echinocardium cordatum (Pennant), upper surface of the empty test or shell without spines. Rhossili Bay strandline, Gower, South Wales, U.K. (3)

Without the spines, five broad grooves are visible. Sea urchins, in common with other Echinodermata like starfish and brittle stars, have pentamerous symmetry – that is, the body design is based on fives.

In the picture below an empty Sea Potato test is shown without spines and the lower surface in view. In life, these seashore creatures burrow between 8 and 15 cm down in the wet sand at low tide level and in the sediments permenantly under water just beyond that (the shallow sublittoral zone).

You can find more information about this species on the marLIN web site.

Sea urchin shell lower surface without spines: The Heart Urchin known as the Sea Potato, Echinocardium cordatum (Pennant), empty test or shell without spines, lower surface view (4)

Revision of a post first published 7 May 2009


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32 Replies to “Sea Potatoes from Gower”

  1. Over the year I have collected a few of these, but as fossils. I did wonder what they were and now I know. They don’t seem to be along the bit of the east coast I live on, though.


  2. Hi, Viv
    Living sea urchins, at least the heart urchin or sea potato, aren’t very common on some parts of the British east coast. You can see their UK distribution map if you look on the marLIN web site:

    Fossil sea urchins mostly occur in chalk and limestone rocks from the Mesozoic era – which are absent from the Suffolk and Norfolk shoreline, and north of about Whitby. There are just a couple of types of fossil urchin in the more recent Caenozoic sediments of East Anglia.
    Where did you find your fossils?


  3. Funnily enough, one in Norfolk! I tripped over it in a molehill along the Cut-off channel between the Ouse and the Wissey!
    Most of the others I found along the Sussex coast, I think. The Norfolk one I have no clue how it came to be there. It may have been imported when they dug the channel and built the banks back in the 50s.
    I’m a bit of a fossil magnet; i can fall over them almost anywhere, even in a ploughed field.
    On another note, stone tools dating from 700,00 years ago (homo erectus or homo heidlebergensis) were found a few miles from where I live. They were dated by the animal bones also found(worked and cut at by said tools) at Pakefield, in Lowestoft. This puts my current town as the oldest known site of human habitation in Northern Europe, and judging by the behaviour of some of the locals on a Saturday night, they’re still here!!!


  4. Although there are only three types of fossil sea urchin that I can find listed for the Crag deposits near to the coast in Norfolk and Suffolk, where you describe your fossil as coming from (further inland – if I have got it right) is close to Cretaceous chalk deposits. So that may explain your find.
    The British Museum (Natural History) has a series of excellent fossil books with line drawings of many examples. If you are curious to find out more about your finds, you could have a look in British Caenozoic Fossils (for fossils of the Crag deposits of Norfolk and Suffolk) and British Mesozoic Fossils (for fossils of the chalk).
    It sounds fascinating that evidence for ancient man has been found so close to your home. The flint used for the stone tools would have been found in great abundance in the chalk.


  5. I have a few fossil books, but will look out for the ones you mention. Yes, we were a long way inland at the time. I like where I live now as I can be at the beach in half an hour ON FOOT, but we’re well away from the erosion zones of Southwold and beyond.
    I did find a mesolithic arrow head on the bit of beach near our home; the fishing trawler sometimes also scoop paleolithic axe heads from the sea bed (from when it was landmass and not under the sea), and those too are in the Natural History Museum, I think.
    It’s a big shame that more has not been made of this funny little town being the site of earliest human occupation of Europe; we haven’t got much here, even though it’s the furthest East you can go in Britain. The Most Easterly Point (Ness Point) is marked by a metal disc set in concrete showing distances to various locations, and a sewage outfall. I take students there(I teach EFL) often every week and feel sad that it’s such a pathetic show of nothing. There was a plan to erect a giant glass sculpture of a herring (think angel of the north but fishy) there but the money seemed to just vanish when various nimbies objected…


  6. You are fortunate to live within such easy walking distance of the seashore. I live relatively near to the sea but it would take me more like half an hour to drive there.
    How lucky to have found an arrow head on the beach. That is really special – to be able to hold in your own hand something that was made and used so long ago. (I did actually once find a beautiful smooth stone axe head on a beach in Scotland when I was 12 but my parents would not let me take it home with me).
    It sounds such an interesting place where you live. Maybe one day they will get that monument built to commemorate (is that how you spell it?) it’s place in history – maybe it was simply that a giant herring was not quite the right thing.


  7. The Herring would have been nicked! the smaller one, at the top of one of the Scores (steep lanes from the top of the cliff to the beach, made by fishermen or by streams) placed there as part of a Heritage trail (the Red Herring trail) by local artists, was first vandalised and then stolen. I haven’t been to check on the other art work down the other trails.
    This is a funny town we landed in two or so years ago; weird. Do you live near Rhossili, then? I’ve camped there twice, some years back, and ridden up the downs. I think it was a painting I did of Sweyen’s How that brought me to your blog here; I checked if there was any other blogs featured on the Rhossili tag and found it.
    Its a shame about the axe head; why wouldn’t they let you keep it? Parents can be odd about smelly things taken home, but an artefact?


  8. It is a pity that people feel the urge to spoil and destroy things – like the Herring. I guess it could be the result of boredom and ignorance. Pakefied sounds interesting even if a bit wierd.
    No, I don’t live near Rhossili but I have known it for a long time. I initially studied natural sciences at Swansea University and did a project on the rocky shore zonation of Burry Holms at Rhossili. Gower has always been a special place to me – and in recent years I have been able to visit it again many times. I’m also fortunate enough to live in Dorset which has the wonderful Jurassic Coast. That’s why I can write about the seashores that I love in both places for the blog.
    The axe head? My parents probably did not understand or appreciate the significance of it.


  9. Ah, I visited Dorset a few times as a child and loved it. We visited the dig site at Hengistbury Head when I was about 15.
    We ended up at The Gower almost by accident; a close friend of mine we were holidaying with after her husband left her, really wanted to go there and walk the Worm’s Head, due to the prominence of this place in a Susan Howatch novel, The Wheel of Fortune. We did so on a swelteringly hot day in August and by the return tirp had run out of water; landing at the pub, parched and dry, I don’t think the first drinks touched the sides. I still tease her about walking the Worm’s Head in slingbacks(or was it kitten heels?) and the yuppies who queue jumped with the immortal words, “Shall we food quickly?” as we struggled to the bar, and then managed to delay us ten minutes while they didn’t “food” quickly. Happy days!


  10. I have never yet made it to the end of the Worm’s Head at Rhossili. It’s quite a trek across that causeway and back between tides. Maybe next time!
    I don’t know whether you are familiar with Chris Elphick’s blog Welcome to Gower. He was talking about the cave right on the end of Worm’s Head just 2 days ago. His site is really excellent and is well worth a visit if you have not seen it already. He was born and bred on Gower and is very knowledgeable about all things Gower including the strange and mysterious. You can get to Welcome to Gower by clicking on the Blog Roll in my side bar or try this


  11. The Sea Potato or Heart Urchin is of course an animal (not a vegetable as the name might suggest).

    Its classification is:
    Phylum Echinodermata
    Class Echinoidea
    Order Clypeasteroidea
    Family Spatangidae
    Genus Echinocardium
    Species – cordatum (Pennant)

    Does that answer your question?


  12. Amazing. Are they edible? Or have people eaten them in the past?
    I found a beach in SW Ireland called Beach of the Potatoes. Do you suppose these creatures might explain the name?
    Cheers Rebecca


  13. Hi, Rebecca
    I expect they are edible but I have no idea what they would taste like. There is not much to eat inside the tests and a person would have to eat an awful lot of them to make any difference to their hunger. Different species of sea urchin are still eaten all over the world but not this particular variety, as far as I know. I couldn’t say with certainty whether the Beach of the Potatoes in SW Ireland has anything to do with “sea potatoes” but somehow think it unlikely – maybe it is a reference to the potato famine or potato growing in the fields around it.
    Best wishes


  14. Hi, thanks v much for the reply. I see what you mean about the sea potatoes. Fascinating anyway. Glad to know about them.
    (Beach of the Potatoes is in a stony, sandy island so I cant see how potatoes grew there but maybe they bought them in and had them delivered on to that beach or maybe lots got washed up there after a storm!!!)
    Best wishes


  15. I was at Kinshaldy beach on the Tay Estuary at the weekend and came across hundreds if these. Is there a reason for their demise? I don’t recall seeing any there before.


  16. Hello, Andy

    I’m always mystified as to the exact events that lead to first one kind of organism and then another to wash ashore in great numbers. I can only assume that in this case the sea urchins had already died naturally and were buried in situ in sediments offshore, and that a combination of particular tides and currents stirred up the seabed and carried the urchin tests ashore. In years of beach-combing I have only occasionally found living sea potato sea urchins on the water’s edge – mostly it is just the empty tests.


  17. My mother used to dig those up when I was a kid, and they’re double the size of what you have captured. Growing up in a small island of American Samoa those were a delicacy. Nowadays people hardly hunt those. Tell you what it’s a taste to die for, better than sea urchin and caviar put together.


  18. Thank you for the comment and information. Sounds like they are delicious. I knew that you could eat sea urchins but I have never done so myself and I don’t think our small English ones would taste as good as your ones!


  19. I have never seen one of these before but we found loads on the beach at Pembrey Country Park (S Wales) today. Great blog, thanks for the info.


  20. I found tons of the tests at the weekend on a beach near Sligo, Ireland. I brought them home but they are extremely delicate and only a few survived the journey. I woUldale love to preserve them but haven’t a clue how to. Does anyone know?


  21. Hello, Margaret. Yes, these sea urchin tests are very fragile. It is amazing that any survive the waves to reach the shore undamaged. I have never tried to preserve them myself but I wonder whether it might be possible to paint them with PVA (polyvinyl acetate) emulsion which is initially a milky fluid but dries clear; it may soak into the test, bonding and strengthening it.


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