Understanding Evolution

Research Profiles : How to survive a mass extinction :

From Stegosaurus to snails

Even in grade school, David Jablonski was set on becoming a paleontologist — but one with a stereotypical bent: a classic, khaki-wearing bone hunter, digging up fossils of the huge animals that once walked the Earth. David was hooked on dinosaurs and fed his fanatical interest through school projects and visits to museums. Then, in college, his interest shifted from big critters to big questions. He realized that basic hypotheses about evolution and ecology could be tested using the fossil record. But in order to study those questions, David needed to test his ideas using a group of organisms with an unusually rich fossil record.

Unfortunately, dinosaur fossils are often few and far between. Fewer than 30 relatively complete T. rex specimens have been unearthed to date! Though this is to be expected based on dinosaurs' large size, decomposition-prone bodies, and land-dwelling lifestyle, it is not welcome news to someone looking for a reliable resident of the fossil record. Clams, snails, and other mollusks, on the other hand, are small, have easily fossilizable shells, and inhabit environments where fossilization occurs relatively easily. In fact, mollusk fossils are abundant enough to be used as road fill in some parts of the country! David had found the ideal paleontological lab rat. He switched from dinosaurs to mollusks and began to gather data.

an outcrop of fossil shells from the Miocene
An outcrop of fossil mollusk shells from the Miocene of Maryland


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Fossil shell photo by Susan Kidwell, University of Chicago

Understanding Evolution © 2018 by The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California