Some of the fossils from Portugal measure nearly three feet long, far more than even the largest trilobite fossils previously known. What's more, the paleontologists found not just one or two trilobite fossils, but thousands in a single area. Scientists call this rich concentration of fossils from a single quarry a "lagerstätte."
The way in which the various groups of trilobite skeletons are arranged provided clues to the lives of these animals. Some groups probably were taking refuge at the time they were buried. Others can be seen giving birth while molting, the scientists say.
The chemistry of the rocks that contain the fossils indicate the area was very low in oxygen content.
Image Credit: Artur Sá