The On The Rocks blog has an interesting post on strange trilobites.  Trilobites come in all shapes and sizes.  Many are “weird”, but probably not any weirder than what is found in the modern, natural world.  The discussion is on both natural deformities from when the animal was alive and deformities caused by the fossilization process.  There is even an example with a bit mark.

Human society has always been intrigued by the physical abnormalities of their peers. In the nineteenth century, ‘freak shows’ were such an attraction that even the American Museum in New York had a permanent exhibition displaying a variety of malformed individuals as entertainment (Saxon 1989). But inherent abnormalities are obviously not restricted to the human species. Pretty much every animal we see in nature – both Recent animals and, as you will see, animals preserved in the fossil record – can have odd defects. Today, we present a fossil freak show with a cast of prehistoric oddities amongst the trilobites, a long extinct group of arthropods that proliferated in the Paleozoic Era.