THE LITTLE BIVALVE Planktomya UNMASKED

Abstract

The enigmatic bivalve Planktomya henseni has masqueraded as a holoplanktonic animal for nearly a century. Allen and Scheltema (1972) showed that all the evidence pointed to a benthic clam with an unusually long planktonic larval stage. This benthic clam has finally been found in the tropical western Atlantic, and appears to be a member of the Family Sportellidae. Comparison with fossil species in this family shows a trend toward a large prodissoconch and apparently a long planktonic larval stage