dcsimg
Image of Irregularia Latreille 1825
Creatures » » Animals » » Echinoderms » » Sea Urchins »

Irregularia Latreille 1825

Irregularia

provided by wikipedia EN

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 no more 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

 src=
Echinolampas ovalis, Middle Eocene, Civrac-en-Médoc, France.
 src=
Echinolampas ovalis, Middle Eocene, Civrac-en-Médoc, France; oral surface.

References

 title=
license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN

Irregularia: Brief Summary

provided by wikipedia EN

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

license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN

Classification

provided by World Register of Marine Species
Although represented here as sister groups, Acroechinoidea, Carinacea and Irregularia actually form a set of nested clades (see image below). Due to the limitations of WoRMS this cannot be reflected in the database at present.
license
cc-by-4.0
copyright
WoRMS Editorial Board
bibliographic citation
Kroh, A. & Smith, A.B. (2010): The phylogeny and classification of post-Palaeozoic echinoids. Journal of Systematic Palaeontology, 8/2: 147-212.
contributor
Andreas Kroh [email]
contributor
Andreas Kroh [email]