These ancient arthropods filled the world’s oceans from the earliest stages of the Cambrian Period, 521 million years ago, until their eventual demise at the end of the Permian, 252 million years ago, a time when nearly 90 percent of life on earth was rather suddenly eradicated. Chelicerates include horseshoe crabs and spiders. They are, however, distantly related to the chelicerates clade.

Trilobites are an extinct clade of Arthropods (like crustaceans). The smallest trilobite fossils are a centimeter or less in size. Some trilobites could swim, others burrowed or crawled around on muddy sea floors. Trilobites are a group of extinct marine arthropods that first appeared around 521 million years ago, shortly after the beginning of the Cambrian period, living through the majority of the Palaeozoic Era, for nearly 300 million years.

Cambrian and Ordovician trilobites generally lived in shallow water. A few, like the agnostids, may have been pelagic, floating in the water column and feeding on plankton. They walked on the bottom, and probably fed on detritus. How did trilobites live?Įcology: Most trilobites lived in fairly shallow water and were benthic. Although they became less abundant in succeeding geologic periods, a few forms persisted into the Permian Period, which ended about 251 million years ago. Trilobites, exclusively marine animals, first appeared at the beginning of the Cambrian Period, about 542 million years ago, when they dominated the seas. But these amazing arthropods were far from the only creatures living in those ancient seas. Trilobites served to neatly bookend the Paleozoic, arising in the Lower Cambrian, some 521 million years ago, and lasting until the end of the Permian.

Udig trilobites