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Photograph supplied by Allen Waters, NASA Langley Research Center
Perhaps the ribs on the shell are formed by folding when the shell is soft.
It is very unusual to find this delicate shell undamaged. It is extremely thin and fragile.
Allen Waters writes:
"I'd be very happy for you to include the angel wing photograph on the
shellbuckling.com website. I was on the first hike in a long time and
having to deal with deep sand in some deep sand in some places- and I found out how out of shape I was the next morning. That said, the hike had me thinking of shell buckling the whole time with all the shells out there-
"The angel wing clam usually spends its life buried several feet in the
sand, and the pressure from the animal inside probably equals the pressure of the sand outside- hence a thin shell with some stiffening is probably sufficient to resist fracture. However, when the animal dies and its shell eventually makes it to the surf zone, the waves are more than
adequate to shatter it. Also, I guess nature has some way of optimizing
the shell thickness as you can see in the photograph, there are various
layers in the shell (the "contour" lines indicating different thicknesses). Also, the "stiffening" folds are more of a 'V' cross-section."
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