The Trilobite Paradoxides

Paradoxides davidis intermedius (Specimen FMNH PE 28971-B, 240mm or 9.25 inches long)

| Paradoxides davidis davidis (Specimen FMNH PE 28974, 200mm or ~8 inches long) | If you think of large arthropods along the rocky coast of New England you probably think of lobsters, but there is another large arthropod literally in these rocky coasts, Paradoxides, a trilobite.  Paradoxides is a large trilobite close to half a meter (one and a half feet) long. There are many species and subspecies of this genus and they have been collected from the Czech Republic, Scandinavia, Wales, Spain, Morocco, Newfoundland, New Brunswick, Maine and Massachusetts. Geologists use these species to correlate rock formations from these different areas. | | This strange geographic distribution and the remarkable similarities of some trilobites from North America and Europe puzzled paleontologists. However, using these trilobites and other fossils, plus paleomagnetic evidence and other clues in the rock record, combined with the Theory of Plate Tectonics geologists have been able to work out the complex story of how these fossil trilobites were distributed to so many different areas. | | | | Paradoxides davidis trapezopyge (Specimen FMNH  PE 25557-A,160mm or 6.25 inches long) |   During the Cambrian Period, 510 million years ago, before there were any lobsters these trilobites crawled along the seafloor, but not off the coast of North America or Europe. They lived in the shallow waters off the coast of a small continent that no longer exists called Avalonia by geologists. |

The specimens were collected and donated to the Field Museum by Riccardo Levi-Setti a professor of physics at the University of Chicago and the inventor of the high-resolution scanning ion microprobe. Levi-Setti enjoys collecting trilobites and has published a book and several scientific articles on trilobites.

Reference

Riccardo Levi-Setti, 1993, Trilobites, University of Chicago Press, Chicago, 342 pages.