Living Fossil The earliest horseshoe crabs were found 450 million years ago as fossils in strata. Many think of them as crabs and crustaceans when in fact they are more related to spiders and scorpions. Under their enormous shell, their bodies also look more like those of spiders.
I had to post this because it is an iconic image from my childhood. As kids we would float over herds (is that the right word) of them on a blow up raft with our faces in the water with masks and snorkels. As a child I was fascinated and scared of them!