The Diadematidae are a family of sea urchins. Their tests are either rigid or flexible and their spines are long and hollow.
Cidaris is a genus of pencil sea urchins.
Loveniidae is a family of heart urchins in the order Spatangoida.
Echinocardium is a genus of sea urchins of the family Loveniidae, known as heart urchins. The name is derived from the Greek ἐχῖνος and καρδία.
Holopneustes is a genus of sea urchins, belonging to the family Temnopleuridae.
Cassiduloida is an order of sea urchins. The group was extremely diverse with many families and species during the Mesozoic, but today, only seven extant species remain.
The heart urchins or Spatangoida are an order of sea urchins.
Cidaridae is a family of sea urchins in the order Cidaroida.
Toxopneustidae is a family of globular sea urchins in the class Echinoidea.
Psammechinus is a genus of sea urchins in the family Parechinidae containing two species:
The Echinometridae are a family of sea urchins in the class Echinoidea.
Caenocentrotus gibbosus is a species of sea urchins of the Family Echinometridae. Their armour is covered with spines. Caenocentrotus gibbosus was first scientifically described in 1846 by L. Agassiz, in L. Agassiz & Desor.
Hemipneustes is an extinct genus of sea urchins belonging to the family Holasteridae.
Irregularia is an extant infraclass of sea urchins that first appeared in the Lower Jurassic.
The Neognathostomata are a superorder of sea urchins.
The infraclassis Carinacea includes most living species of regular sea urchin, and fossil forms going back as far as the Triassic.
Toxopneustes roseus is a species of sea urchin from the East Pacific. It is sometimes known as the rose flower urchin or the pink flower urchin. Like the related flower urchin, they are venomous.
Temnopleuridae is a family of sea urchins in the infraorder Temnopleuridea.
Tetrapygus is a genus of sea urchins in the family Arbaciidae. It is a monotypic genus and the only species is Tetrapygus niger which was first described by the Chilean naturalist Juan Ignacio Molina in 1782. It is found in the southeastern Pacific Ocean on the coasts of South America.
