June 3. Archimedes

Today I want to talk about a bryozoan, a colonial animal somewhat like corals but probably more closely related to brachiopods. You may recall that they were the only phylum that, so far as we know, was NOT established before or during the Cambrian explosion but developed later, during the Ordovician. And they do survive to this day.  

During the Mississippian, the warm shallow seas of North America harbored plenty of life, including diverse bryozoans. But the screwiest of all is a group named Archimedes.  

Archimedes was the Greek philosopher who invented the screw as a way to lift water.

Archimedes wortheni

Fossils of the bryozoan genus Archimedes look just like screws. In life, the individual zooids that comprised the colony had lattice-works extending away from the long, spiraling skeletal substrate of the colony, but the fossils usually preserve only that skeletal backbone, and it looks like a screw. The name was first applied by the American geologist David Dale Owen in 1828.

They’re really pretty common, and you find them typically something like one to four inches long, or shorter broken fragments. Screws can be left-handed or right-handed, and so are Archimedes bryozoans. They began and were abundant during the Mississippian and survived about 108 million years, until the mass extinction at the end of the Permian Period.

Archimedes bryozoans also look an awful lot like fusilli pasta, and when you get a lot of geology students together in a place like geology field camp and serve it to them, you can bet that they’ll start calling it Archimedes noodles. I’ve had it dozens of times.

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Two geological birthdays today. James Hutton,, who formulated the theory of uniformitarianism and many of the concepts that laid the groundwork for the modern science of geology, was born June 3, 1726, at Edinburgh, Scotland. Check the posts for March 7 and May 4 for more about him. Lee Suttner, one of my professors of geology at Indiana University, was born June 3, 1939, in Wisconsin. If I’m a decent teacher of geology, I owe it to Lee for sharing his style of asking leading questions, rather than telling. It’s a style I admire and try to emulate when I can. Happy birthday, all.

—Richard I. Gibson

David Dale Owen and the naming of Archimedes

Drawing from an old textbook (public domain)