Date: Mon, 10 May 1999 13:15:12 -0500
Reply-To: Conchologists of America List <CONCH-L@UGA.CC.UGA.EDU>
Sender: Conchologists of America List <CONCH-L@UGA.CC.UGA.EDU>
From: "Andrew K. Rindsberg" <arindsberg@OGB.GSA.TUSCALOOSA.AL.US>
Subject: more shelling stories and beach safety
A couple of my best shelling days involved sand dollars instead of
mollusks. I've always liked sand dollars, but they don't usually survive
the trip up the surf to the shore intact. Long ago and far away, during my
wild undergrad days in California in the early 70's, I was on the
cliffbound but sandy shore of San Gregorio Beach, about halfway between San
Francisco and Monterey. As at most central California beaches, complete
shells were few.
The common sand dollar of this coast is Dendraster excentricus. This
species is indeed eccentric, in more ways than one. Unlike other sand
dollars, it is slightly asymmetrical. And it has a peculiar behavior: When
conditions are right, the animal props itself on edge in the sand to feed
on particles directly from the water. It evens ingests and stores heavy
magnetite sand grains in its gut to act as a "weight belt".
One day at San Gregorio, I was delighted to pick up a single Dendraster
excentricus. And later in the day, as I was collecting shells from the
cliff in Pliocene sandstone, I found another. The second sand dollar was at
least a couple of million years old. I could see no significant anatomical
differences between them. Times change, but not always quickly, it seems.
Yet the landscape had changed beyond recognition in the same interval.
Another day on a beach farther south, on Monterey Bay, where the dunes
follow the strand for miles and miles, I found another sand dollar. And
then another, and another. I waded into the water, reasoning that sand
dollars live there, so I would find more there. Then I found the mother
lode of all sand dollars. I could reach down and feel around in the surf
with my fingers, finding the smooth tests of echinoderms every few paces. I
went into a kind of collecting frenzy, and stayed in the water for about
two hours, collecting about 200 (long dead) sand dollars. My feet were
mottled blue and pink with the cold, and were so numb that it was like
walking on wooden stumps. I wasn't a scientist yet, of course. But later, I
looked at this collection of many sand dollars, and noted the individual
variations in form, and the occasional specimens that had a bite taken out,
where a fish had fed on a bed of upright sand dollars. That was not just
collecting, but research.
Still, research without communication is not science.
Later, I wrote a term paper on the fossils in the cliffs at San Gregorio
Beach, and still later gave my first (and worst ever!) talk on their
paleoecology at a state academy of science, resulting in my first
publication, an abstract on California paleontology lost in the obscure
pages of a Georgia journal. Not very influential, but that was science.
Of course, I didn't mention in the talk that San Gregorio was a nude beach.
Andrew K. Rindsberg
Geological Survey of Alabama