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Polished Sand Dollar/Pansy Shell Echinoid Fossil

R 220.00
SKU: S312

Polished Sand Dollar/Pansy Shell Echinoid Fossil

These beautifully polished pansy shells are from Madagascar and are Triassic (251 million and 199 million years ago) in age.   

Origin: Madagascar

Average Size: Between 70mm and 75mm in diameter

The term sand dollar (known as a pansy shell in South Africa) refers to species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some of the species in this order are not quite as flat and are known as sea biscuits. 

Sand dollars, like all members of the order Clypeasteroida, possess a rigid skeleton called a test. The test consists of calcium carbonate plates arranged in a fivefold symmetric pattern.  In living individuals, the test is covered by a skin of velvet-textured spines which are covered with exceedingly small hairs (cilia). Coordinated movements of the spines enable sand dollars to move across the seabed. The velvety spines of live sand dollars appear in a variety of colours—green, blue, violet, or purple—depending on the species. Individuals which are very recently dead or dying (moribund) are sometimes found on beaches with much of the external morphology still intact. Dead individuals are commonly found with their empty test devoid of all surface material and bleached white by sunlight.

The bodies of adult sand dollars, like those of other echinoids, display radial symmetry. The petal-like pattern in sand dollars consists of five paired rows of pores. The pores are perforations in the endoskeleton through which podia for gas exchange project from the body. The mouth of the sand dollar is located on the bottom of its body at the center of the petal-like pattern. Unlike other urchins, the bodies of sand dollars also display secondary front-to-back bilateral symmetry. The anus of sand dollars is located at the back rather than at the top as in most urchins, with many more bilateral features appearing in some species. These result from the adaptation of sand dollars, during their evolution, from creatures that originally lived their lives on top of the seabed (epibenthos) to creatures that burrow beneath it (endobenthos).

The common sand dollar, Echinarachnius parma, is widespread from the intertidal zone to considerable depths in the ocean waters of the Northern Hemisphere. It can be found in temperate and tropical zones. The keyhole sand dollar (three species, genus Mellita) is found on a wide range of coasts in and around the Caribbean Sea.

The term sand dollar (known as a pansy shell in South Africa) refers to species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some of the species in this order are not quite as flat and are known as sea biscuits. These specimens are from Madagascar and are Triassic (251 million and 199 million years ago) in age.   

Sand dollars, like all members of the order Clypeasteroida, possess a rigid skeleton called a test. The test consists of calcium carbonate plates arranged in a fivefold symmetric pattern.  In living individuals, the test is covered by a skin of velvet-textured spines which are covered with exceedingly small hairs (cilia). Coordinated movements of the spines enable sand dollars to move across the seabed. The velvety spines of live sand dollars appear in a variety of colours—green, blue, violet, or purple—depending on the species. Individuals which are very recently dead or dying (moribund) are sometimes found on beaches with much of the external morphology still intact. Dead individuals are commonly found with their empty test devoid of all surface material and bleached white by sunlight.

The bodies of adult sand dollars, like those of other echinoids, display radial symmetry. The petal-like pattern in sand dollars consists of five paired rows of pores. The pores are perforations in the endoskeleton through which podia for gas exchange project from the body. The mouth of the sand dollar is located on the bottom of its body at the center of the petal-like pattern. Unlike other urchins, the bodies of sand dollars also display secondary front-to-back bilateral symmetry. The anus of sand dollars is located at the back rather than at the top as in most urchins, with many more bilateral features appearing in some species. These result from the adaptation of sand dollars, during their evolution, from creatures that originally lived their lives on top of the seabed (epibenthos) to creatures that burrow beneath it (endobenthos).

The common sand dollar, Echinarachnius parma, is widespread from the intertidal zone to considerable depths in the ocean waters of the Northern Hemisphere. It can be found in temperate and tropical zones. The keyhole sand dollar (three species, genus Mellita) is found on a wide range of coasts in and around the Caribbean Sea.