Trilobites

Trilobites — the word means “three lobes” and refers to the three axial lobes that divide the body length-wise — were on Earth for some 270-300 million years. None survived the Permian Extinction 240 million years ago. They were diverse and widely spread across the planet; their fossilized remains are found on all continents today. These remains have been classified into ten known Orders and, astonishingly, more than 20,000 species. They are very well represented in the fossil record and are probably the most recognizable ancient life-form.These come from the Wheeler Shale deposits near Delta, Utah. Humans have been intrigued by these ghostly remains for a long time now: some have been found in 50,000 year old burial mounds. How could I resist?It is of course the patterns of their chitinous exoskeletons that we look at now when we look at these fossils. Although named for their axial lobes, they are also tripartite, with head (cephalon), thorax, and pygidium. Does this remind you of a certan tattoo? They are, after all, ancient relatives of horseshoe crabs.

Coincidently, another Matthew Wills is an expert on the subject.