heart urchin

plural heart urchins

1. Any echinoderm of the class Spatangoida.

   Red heart urchins, like other heart urchins, are usually buried under the sand and are only seen on rare occasions.

   1996, Marty Snyderman, chapter I, in Guide to Marine Life: Caribbean, Bahamas, Florida, page 129

   2 more examples

   Spatangoids constitute a monophyletic group of heart urchins that appears in the early Cretaceous (145 M.Y. ago) and ranges to the Recent.

   2003, Gunther J. Eble, “Developmental Morphospaces and Evolution”, in James P. Crutchfield, Peter Schuster, editors, Evolutionary Dynamics, page 47

   The class of animals (Echinoidea) that sea urchins belong to includes sand dollars and heart urchins. Sand dollars are flat, while heart urchins are oval, covered in short spines with longer spines down their back.

   2007, Marian Armstrong, Wildlife and Plants, 3rd edition, volume 16, page 967

   Synonyms: spatangoid