A Sand Dollar is a Sand Dollar or Is It?

What a surprise this morning when I finally took out the sand dollars that I had collected on a beach in Washington State last summer. Sitting in my front yard for the last month have been the sand dollars and starfish that I collected from the beach at Ft. Myers Beach last winter. I wanted to dry out the Washington specimens as well. My surprise was that they were very different and I hadn't noticed at all! So of course an online inquiry was in order and I found this great website at the University of Michigan with pictures and scientific names (http://animaldiversity.ummz.umich.edu/).

Seems there are two distinct versions of the flat old sand dollars that we are used to looking at -- one is flat and has no holes in it and one is flat and has five or six holes in it. The one with no holes is also heavier and fatter and generally a bit smaller in size. This is the one I collected in Washington state. The one with the holes in it is the one I found down in Florida.


East Coast Ft. Myers Beach sand dollar with only five holes (Keyhole Sand Dollar, Mellita quiquiesperforata ). I think this is a variety of the one with six holes in it(Leodia sexiesperforata -six holed keyhole urchin ).

This is the variety I found out on the West Coast last summer (Dendraster excentricus ).



What I didn't know was that what we call sea urchins (those spiny black things) as well as starfish and a number of other weird non-mollusk sea living animals were also in this phylum (Echinodermata or Echinoderms). Echinoderms only live in sea water and have no varieties that live on land or fresh water. I picked up quite a few of sea urchins and starfish as well last winter as well while down in Florida.

There was one amazing day in Florida, the day after a rather stormy couple of days at the beach. About three miles down the beach, there was debris piled 2 feet high in places and filled with dead sea urchins and sand dollars. The shelling was beyond spectacular as well. I was fortunate to have seen many species of shells and othe sea creatures that normally I would not have seen. I can imagine that after a hurricane, it would be beyond belief!