Sand dollars are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits. Sand dollars can also be called "sand cakes" or "cake urchins".
Crassostrea is a genus of true oysters containing some of the most important oysters used for food. Some species in the genus have been moved to the genus Magallana.
Echinarachnius parma, the common sand dollar, is a species of sand dollar native to the Northern Hemisphere.
Leo George Hertlein was an American paleontologist and malacologist who studied the Recent and fossil mollusks of the eastern Pacific Ocean.
Diadema setosum is a species of long-spined sea urchin belonging to the family Diadematidae. It is a typical sea urchin, with extremely long, hollow spines that are mildly venomous. D. setosum differs from other Diadema with five, characteristic white dots that can be found on its body. The species can be found throughout the Indo-Pacific region, from Australia and Africa to Japan and the Red Sea. Despite being capable of causing painful stings when stepped upon, the urchin is only slightly venomous and does not pose a serious threat to humans.
Coelopleurus is an extant genus of echinoids with fossil records dating back to the Eocene, with remains found in Europe and North America.
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.
Echinarachnius is a genus of sand dollars, belonging to the family Echinarachniidae.
Dendraster excentricus, also known as the eccentric sand dollar, sea-cake, biscuit-urchin, western sand dollar, or Pacific sand dollar, is a species of sand dollar in the family Dendrasteridae. It is a flattened, burrowing sea urchin found in the north-eastern Pacific Ocean from Alaska to Baja California.
Ammotrophus arachnoides is a species of sand dollar of the family Arachnoididea. Their external skeleton, known as a test, is covered with spines. It belongs to the genus Ammotrophus and lives in the sea off southern Australia. Ammotrophus arachnoides was first scientifically described in 1938 by Hubert Clark.
Ammotrophus cyclius is a species of sand dollar of the family Clypeasteridae. Their external skeleton, known as a test, is covered with spines. It belongs to the genus Ammotrophus and lives in the seas off southern Australia. Ammotrophus cyclius was first scientifically described in 1928 by Hubert Clark.
Ammotrophus platyterus is a species of sand dollar of the family Clypeasteridae. Their armour is covered with spines. It came from the genus Ammotrophus and lives in the sea. Ammotrophus platyterus was first scientifically described in 1928 by Hubert Clark.
Dendraster ashleyi is an extinct species of sand dollars of the family Dendrasteridae. Fossil of this species have been found in the Pliocene of California, about 5 Mya. They reach a diameter of about 3.5 cm.
Dendraster gibbsii is an extinct species of sand dollars of the family Dendrasteridae. Fossil of this species have been found in the Pliocene of California. They reach a diameter of about 3.5 cm.
Heliophora orbicularis, also known as the West African Sand Dollar, is a small sand dollar in to the family Rotulidae, and the only species in the genus Heliophora. It, and other members of Rotulidae have been found in West African marine strata from the Late Miocene onward. Like the related Rotula, it is still extant.
Irregularia is an extant infraclass of sea urchins that first appeared in the Lower Jurassic.
The Neognathostomata are a superorder of sea urchins.
Schizaster is a genus of heart urchins belonging to the family Schizasteridae. The type species of the genus is Schizaster studeri.
Clypeasteridae is a family of sea urchins in the order Clypeasteroida. This family was first scientifically described in 1835 by the Swiss-American biologist Louis Agassiz.
Encope emarginata, a notched sand dollar, is a marine echinoid ranging the western Atlantic ocean. They are best known for their bioturbation in the sediment, relationship with crabs, and their widespread distribution.
