Things We Do Not Talk About

There is an entire Class of animals that we have not really discussed. They are always right there when we look up fossils. We should take a closer look at these alien, but very familiar, animals. Appearing between 540 and 520 million years ago, the Class we know as the Trilobites, are ovoid, sometimes clearly showing appendages, arthropods that existed until shortly before the end Permian extinction. No existing direct descendants of trilobites exist today. However, in the age of the greatest diversity of trilobites, from the Early Cambrian to the end-Permian, there are 11 known orders of trilobites that includes more than 30 genera and many more species. Talking about "the trilobite" fossils is actually quite misleading. Usually when someone mentions trilobites they conjure up images of trilobites such as Ogygopsis, or Meroperix. Perhaps you might think of a less ovoid member of the group, one that has large head elements, like Paradoxides, or with long tail structures, like Cheirurus. We will look at general anatomy of trilobites tomorrow, then, during the rest of the week, we will discuss some specific examples of genera or species of iconic trilobites.