CINCINNATI, Ohio -- When some scientists first floated the idea that an ancient crinoid called Uintacrinus, could float on the top of the sea, other scientists were skeptical. Modern day relatives such as sea stars all live on the ocean bottom in tightly packed colonies.
David Meyer, a professor of geology at the University of Cincinnati, will present evidence at the Geological Society of America annual meeting Monday, October 20 supporting the idea that Uintacrinus could float. However, Meyer's model goes further by proposing a brand new model to explain the 85 million-year-old Cretaceous crinoid's unexpected buoyancy. It's a model that began with a few random thoughts.
"In thinking about this, I got to thinking about insects like water striders," said Meyer. "There are aquatic insects that live on the surface of the water and use surface tension. They walk on water."
As Meyer explored this phenomenon, he discovered that insects that can walk on water have very long legs compared with their body size. Uintacrinus has similar properties. It looks a bit like a tiny octopus with a golf-ball sized body and ten long arms stretching out from the center.
"I tried to calculate how long the arms of the Uintacrinus would be. We found the length of their arms could be one meter long, so they'd have a diameter of two meters and that's just the arms alone. The little extensions of the arms called the pinnules give you even more length. We found these crinoids have much greater arm length than any known crinoids."
Using a well established formula involving surface tension,
Meyer discovered that all those arms could easily keep
Uintacrinus afloat if the arms were spread out over the surface
of the water. In fact, that arrangement would support an animal
nearly six times heavier than Uintacrinus. It would also make it
easy for the crinoid to pull food particles and microscopic
plankton out of the water, since that food tends to accumulate
right at the sea's surf
Contact: Chris Curran
University of Cincinnati