This is such a lovely plaque with the pale pink of the sea urchins shell, or “test” still clearly evident in the cream limestone – but just a little sad that so many expired at once in such a small space.
Sea urchins are from the class of Echinoidea and are found in oceans all over the world. Many species became extinct towards the end of the Paleozoic era. Echinoid is derived from the Greek “Echinodermate” meaning spiny skin. They are globe shaped and vary in size. They typically range from 3 to 20 centimetres, but the larger species can achieve over 30 centimetres.
The underside of the sea urchin is called the oral surface as it has a mouth (the top is the aboral surface). They have tube feet which are moved by a water vascular system, which is a system of canals connected to the tube feet. Movement is by achieved by contracting muscles to push the water into the feet thereby forcing them into the surface to rise up or relaxing the muscles to retract the feet thereby lowering.
The plaque illustrated here originates from southern France and is between 20 to 40 million years old. Whole fossilised sea urchins are relatively rare as frequently the shell is crushed leaving only small fragments.
Charlotte
© Copyright Charlotte M Bailey 2012
