Heliophora Fossil Flat Sea Urchin Prehistoric Echinoderma Tertiary Miocene Collection (2)

Sea Urchin Fossil West African Sand Dollar Sea Biscuit mm 36 x 36 x 6 gr 8.1 Heliophora orbicularis Invertebratas Echinoderma Echinozoa Echinoidea Irregularia Prehistoric Extinct Flat Marine Urchins Cenozoic Tertiary Miocene Collecting Paleontology Museum.

Pleasant fossil find of Sea Urchin Irregularia Rotulidae from the Miocene, representative collectible specimen of good quality and in best condition, with evident and appreciable details of the shape of the flattened exoskeleton, the digitations of the crown and the oral and aboral foramens on the ventral side.
The find has the crown not perfectly intact, but in any case in fair condition, considering that these fossils are rare enough to find complete and well preserved like this specimen.
Only a piece, as in photos.

Heliophora orbicularis is a small flat Sea Urchin (Echinoidea Irregularia), of the Rotulidae family, known more familiarly as "sand dollars".
They have been found in marine fossiliferous layers of West Africa, from the late Miocene onwards. Like the current Rotula, it still exists.
Individuals of H. orbicularis are very particular, both for their peculiar morphology and for the notable diversity in the individual specimens. This genus has an extremely variable shape, from circular to oval. The indentations of the crown, which is difficult to find intact, may remain limited to the posterior margin or may be located along the entire margin. Furthermore, they can be very superficial or quite deep, forming long digits. These, when present, are very fragile, and prone to breakage.
H. orbicularis lived in large groups in very shallow lagoon and estuary waters, usually slightly buried in mud.
Food particles are collected on the substrate by the ambulacral pedicels, and conveyed into the grooves of the oral area. Here they were incorporated into a strip of mucus and introduced into the mouth, which is located in the center of the oral side of the exoskeleton. The anal opening is located in a more marginal position, as in all flat urchins or Irregularia, compressed latero-laterally, with migration of the two openings of the digestive system which come to be close to each other, rather than at opposite poles of the body, as in Regularia hedgehogs.
These sand dollars are found along the western coast of the Sahara, from Senegal to Angola.