Hemicidaris Fossil Pensil Sea Urchin Prehistoric Echinoderma Mesozoic Jurassic Collection

Pencil Sea Urchin Fossil Urchin mm 37 x 18 h gr 31.2 Hemicidaris intermedia Invertebrata Echinoderma Echinozoa Echinoidea Regular Prehistoric Extinct Mesozoic Jurassic Collecting Paleontology Museum.

Pleasant fossil find of Hedgehog Regularia Hemicidaridae from the Jurassic, representative collectible specimen of good quality and in a fair state of conservation, with evident and appreciable details of the exoskeleton plates and the numerous radioles or tubercles on which the long, unpreserved sharp spines were inserted.
Only a piece, as in photos.

Hemicidaris (L. Agassiz, 1838) is an extinct genus of Regularia sea urchins of the Hemicidaridae family, which lived between the Middle Jurassic and the Lower Cretaceous (between 170 and 120 million years ago).
The skeleton of these echinoids was rounded and the apical disk rather small, with an upper part very similar to that of the current Cidaris, with the anus surrounded by some plates. The buccal orifice opened on the lower edge, slightly flattened. This was large and had a particular ornamentation; the "Aristotle's lantern", however, was equipped with striated teeth. The radioles were decidedly large and the spines were very long and sharp. The animal's skeleton was small, with a diameter of about 3-4 centimeters.
Hemicidarids lived on the seabed, among the rocks, supporting themselves thanks to the pedicel present on the ventral surface. They fed on hard surfaces, thanks to five robust teeth.
Fossil remains of species belonging to this genus have been found in Europe, North Africa, East Africa and the Arabian Peninsula.
Hemicidarid fossils are frequent in Oxfordian and Kimmeridgian coral deposits. At the moment 13 species are ascribed to the genus, including H. intermedia.