-Animals (Kingdom Animalia)

-Echinoderms (Phylum Echinodermata)

-Sea Urchins and Sea Cucumbers (Subphylum Echinozoa)

-Sea Urchins, Sand Dollars, and Heart Urchins (Class Echinoidea)

-Pencil Urchins (Subclass Cidaroidea)

-Pencil Urchins (Order Cidaroida)

-Superfamily Cidaroidea

-Family Cidaridae

-Subfamily Cidarinae

-Genus Eucidaris

-Slate Pencil Urchin (Eucidaris thouarsii)

The Slate Pencil Urchin (Eucidaris thouarsii) is species of sea urchin belonging to the Cidaridae family. It is primarily found in the eastern Pacific Ocean. Characterized by thick, blunt, pencil-like spines that are often shorter and more irregularly arranged. The spines are usually brown, gray, or reddish.