Английская Википедия:Irregularia

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Шаблон:Short description Шаблон:Automatic taxobox

Irregularia is an extant infraclass of sea urchins that first appeared in the Lower Jurassic.

Description and characteristics

These particular sea urchins are distinguished from other sea urchins by their irregular shape: the anus and often even the mouth are at the two poles of the test, creating a bilateral symmetry instead of the classical 5-fold symmetry of echinoderms. The group includes the well known heart urchins, as well as flattened sand dollars, sea biscuits and some other forms. Most of them live inside the sediment, moving in thanks to their particular spines, and feed on its organic fraction.

Taxonomy

Файл:MHNT - Hemipneustes pyrenaicus - 1.jpg
Fossil of an Hemipneustes pyrenaicus (Holasteroida).
Файл:Ruhrmuseum-Ebene-12-Naturkunde3784.jpg
Fossil of a Conulus subroundatus (Echinoneoida).
Файл:Scutella subrotunda (Leske, 1778).JPG
Шаблон:Center
Файл:Echinolampas ovalis M Eocene Civrac-en-Médoc France.JPG
Echinolampas ovalis, Middle Eocene, Civrac-en-Médoc, France.
Файл:Echinolampas ovalis M Eocene Civrac-en-Médoc France oral.JPG
Echinolampas ovalis, Middle Eocene, Civrac-en-Médoc, France; oral surface.

References

Шаблон:Taxonbar


Шаблон:Echinoidea-stub