I knew I’d seen this exact shape before (the dark one on the left) – the distinct, lopsided bowl, the pronounced “beak” and the pastry-like layers of shell growth. I was shucking my way through a sack of Hog Island oysters, freshly harvested from Tomales Bay in Northern California, and hustling to get an order of 12 off the raw bar and out to some hungry customers. I set the provocative little bivalve aside on the ice, and forgot about it until clean up later that evening. Then the connection came clearly – this odd-shaped oyster looked just like one I had seen last summer (the grey one on the right), an oyster from a very different time and place…. a fossil from an outcropping of Mancos Shale in central Utah (photo below), preserved in stone from the mid-Cretaceous – around 100 million years ago!  

The similarities between the two shells are stunning. What is even more stunning is the obvious question underlying the “sisters from a different mister” – why? Why are these shells so similar, given all that has changed on planet Earth in 100 million years? How many animals living today look unchanged from their ancestors of the Cretaceous? Not many. So what is it about oysters, and the design of oysters, that makes this possible? The answer may lie in the nature of the intertidal habitat that oysters call (and many other marine invertebrates) call home.

to be continued……