1. Trilobites are extinct arthropods (distant relatives of modern lobsters, horseshoe crabs, and spiders). They existed for approximately 300 million years from the Lower Cambrian Period (521 million years ago) to the end of the Permian (240 million years ago) and have been found on every continent on Earth.  Photo by Denis

    Trilobites are extinct arthropods (distant relatives of modern lobsters, horseshoe crabs, and spiders). They existed for approximately 300 million years from the Lower Cambrian Period (521 million years ago) to the end of the Permian (240 million years ago) and have been found on every continent on Earth. 

    Photo by Denis

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