Oldest shrimp fossil documented

The fossil, drawn from the dark-colored, siliceous Woodford Shale in southern Oklahoma, was discovered by Ohio University paleontologist Royal Mapes and sent to Schweitzer and Feldmann for identification.

Through a grant from the National Science Foundation, Schweitzer and Feldmann quickly went to work cleaning, photographing and drawing sketches of the fossil, examining its tail segments, legs, muscle structure and rostrum (a spine-like protrusion from the head). Remarkably preserved, the specimen displays rare soft tissue detail. The fossil was dated to the Devonian Period – making the fossil the earliest known shrimp and one of the two oldest decapods, both from North America. "This recent discovery means they date back as far as 360 million years – much earlier than dinosaurs, and much earlier than traditional views held," says Schweitzer.

Over the course of three months, Schweitzer and Feldmann developed a report on their findings titled "The Oldest Shrimp and Remarkable Preservation of Soft Tissue," which was published in the November 2010 Journal of Crustacean Biology.

Other researchers, working under the same National Science Foundation Grant, are working on a family tree of all decapods using DNA. The fossil Schweitzer and Feldmann identified, named Aciculopoda mapesi after its discoverer, permits these researchers to put a geologic age on shrimp and provides a molecular clock, or a starting point, for them to work from. "Now we know there are more than 150 million years of shrimp fossil records that are missing. We need to look more closely at arthropod evolution, which I believe will result in new and surprising results about evolutionary patterns in general," says Schweitzer. "We have a lot more fossils to find."

In September 2010, Schweitzer and Feldmann presented the findings of their grant research at the Geological Society of America's Annual Meeting and Exposition, Reaching New Peaks in Geoscience. The fossil shrimp now resides in the Smithsonian Institution, where they worked as visiting researchers in 2008.

The husband-wife team believes that more fossils of this kind will be found in black shale and Triassic rocks where soft-bodied animals can be preserved. With upcoming plans to dig in Argentina, they hope to find more specimens that will help piece together the mysterious puzzle of decapod fossil records.

Schweitzer, who conducted her thesis and dissertation on Pacific Coast decapods, has published nearly 100 papers on the Decapoda. Together with Feldmann, whose research began in the 1970s, they have accumulated an encyclopedic knowledge of decapod records, earning them the nickname, "The Decapod People," by their peers internationally. Over the past five years, they have visited nearly every major decapod collection in the world.

During her sabbatical in spring 2010, Schweitzer began writing a diagnosis for every genus, family and superfamily of decapods, and she is also working on the Decapoda volume in the encyclopedia of all invertebrate animals, the Treatise on Invertebrate Paleontology, as the most recent documentation is outdated.