<P> 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 , in the course of their evolution , from creatures that originally lived their lives on top of the seabed ( epibenthos ) to creatures that burrow beneath it ( endobenthos ) . </P>
<P> 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 , in the course of their evolution , from creatures that originally lived their lives on top of the seabed ( epibenthos ) to creatures that burrow beneath it ( endobenthos ) . </P>
what type of symmetry do sand dollars have
what type of symmetry do sand dollars have
radial symmetry secondary front - to - back bilateral symmetry
radial symmetry secondary front - to - back bilateral symmetry