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Fossil of Acrocidaris, an extinct sea urchin. Echinoid fossils are the fossilised remains of sea urchins, spiny marine invertebrates that live on the seabed. Humans have been interested in these fossils for millennia, have considered them lucky, have imbued them with magical powers and linked them to their deities. [1]
Specifically, the term "sea urchin" refers to the "regular echinoids", which are symmetrical and globular, and includes several different taxonomic groups, with two subclasses: Euechinoidea ("modern" sea urchins, including irregular ones) and Cidaroidea, or "slate-pencil urchins", which have very thick, blunt spines, with algae and sponges ...
Sea urchin tests showing the ball parts of the ball and socket joints that articulate with the spines Iconaster longimanus, the icon seastar, showing plate ossicles. Ossicles have a variety of forms including flat plates, spines, rods and crosses, and specialised compound structures including pedicellariae and paxillae.
Echinus is a genus of sea urchins.Sea urchins are echinoderms that are typically spherical or flattened with a covering of spine-like structures. Sea urchins tend to be important members of their ecosystems by grazing on other organisms and stabilizing populations.
The Echinothurioida are an order of sea urchins in the class Echinoidea. Echinothurioids are distinguished from other sea urchins by the combination of a flexible test and hollow spines. The membrane around the mouth contains only simple plates, in contrast to the more complex mouth parts of their close relatives, the Diadematoida. They are ...
Reconstructive diagram (left) of a fossil (right) of the Ordovician sea urchin Bothriocidaris. The short spines which were attached to the tubercles are not drawn. †Bothriocidaris †Bumastus †Bumastus orbicaudatus †Calymene †Cameroceras †Ceratopsis †Ceraurinella †Ceraurinus †Ceraurus †Charactoceras †Chasmatopora ...
Last year, sea urchins in the Caribbean started getting sick — shedding their spines, dying off and throwing reef ecosystems into chaos. “The case is closed,” said study author Mya Breitbart ...
These tubercles hold massive spines, thick, strong and often very long, and showing sometimes odd shapes (thorny spines, fans, clubs, Christmas trees [1]...). [ 2 ] [ 3 ] The order Cidaroida is the basalmost of current sea urchins, and most of the species included in this family are abyssal, even if a handful of species remain quite common in ...
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