Tribrachidium

About 550 million years ago, some very strange animals lived in the world's ocean. They had no shells, bones, or other hard parts, but did leave behind fossil impressions. Tribrachidium, shown here, is one of these unusual fossils. Scientists are still not sure what kind of organism Tribrachidium was, but some suspect that it was related to today's jellyfish.

Tribrachidium © 2001 Lisa Gershwin, UCMP