Euechinoidea
Euechinoidea
The Euechinoidea include with the exception of the lance urchins ( Chidaridae ) all extant sea urchin species. They are divided into four super-order. The Euechinoidea there since the Triassic.
System
About orders / orders / families ( incomplete)
- Atelostomata Zittel, 1879 Heart Hedgehog ( Spatangoida )
- Diadematoida Diadem Sea Urchin ( Diadematidae )
- Genuine sea urchin ( Echinoida ) Drilling and pencil sea urchin ( Echinometridae )
- Strongylocentrotidae
- Sand dollars ( Clypeasteroida )
Diadematacea and Echinacea were previously combined as Regularia ( sea urchin with radially symmetrical calcareous skeleton ), and Atelostomata gnathostomata formed the Irregularia ( sea urchin with bilateral symmetry). This is now considered obsolete because it occur in the Echinacea both regular and irregular shapes.