Spatangoida

Heart urchins
Temporal range: Lower Cretaceous–recent
Spatangus purpureus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Echinodermata
Class: Echinoidea
Subclass: Euechinoidea
Infraclass: Irregularia
Superorder: Atelostomata
Order: Spatangoida
L. Agassiz, 1840
Suborders

The heart urchins or Spatangoida are an order of sea urchins.

Their body is a somewhat elongated oval in form, and is distinguished by the mouth being placed towards one end of the animal, and the anus towards the other. As a result, heart urchins, unlike most other sea urchins, are bilaterally symmetrical, and have a distinct anterior surface. The presence and position of the mouth and anus typically give members of this group the distinct "heart" shape from which they get their name.

Heart urchins have no feeding lantern, and often have petaloids sunk into grooves. They are a relatively diverse order, with a number of varying species.