Day 8: The Search for Rodent Teeth

Today we split into two groups: The Lago Bayano diggers and the Corozal sifters. I was a Corozal sifter.

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While our trips to Alajuela and Bayano are fun enough, driven by the easy, instant gratification of finding 10-million-year-old fossil remains of mollusks, echinoderms, sharks, crocodylians, turtles, and the occasional mammal, it’s the behind-the-scenes micro-fossil hunter, toiling in sludge and mud, who has to truly work through the sediments like a hero. Granted, the goal of our work was not the collection of the most micro of micro-fossils (pollen and plankton, for example), but our quarry was pretty darn small. Tiny shark teeth, tiny reptilian vertebra, tiny rodent teeth: the itty-bitty fossil remains of the rich fauna found in the Panamanian isthmus. Our rodent expert, Gary Morgan, is deeply interested in the evolution of rodents in the New World, and hopes to find South American rodent clues in the grit and gravel we carefully washed today.

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Why would a rodent tooth be in a shallow sea from 10 million years ago? There are several plausible explanations for why a rat tooth would be found next to a Megalodon tooth, and I will leave this for the reader to ponder.

We began with Bayano dirt, and finished the day with Alajuela dirt. Annie, Becca, and I caught the sediments in three different mesh-lined frames. This fractional slurry-sifting gave us three degrees of coarseness of sediments, which you can see below.

These nice cedar frames come from Cross Creek Archaeological Supply and I would like to have a few for my classroom. Want to see a video of them in action?

Can you find any shark teeth in the above medium-coarse Bayano sediment sample?

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When these samples are dry in a few days, they will get washed and sifted AGAIN to help Gary reduce his sediment load on the plane. In Albuquerque, Gary and his volunteers will pore over these samples with magnifiers and microscopes in search of tiny bits of rodents and other animals.
It was another great day in the field, with fine colleagues and terrific teamwork. Nobody got hit by a wayward coconut; we can only hope that the Bayano cohort stayed safe from the crocodiles and otters.

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