While on a geology field trip through Texas and New Mexico, we stayed at Monahans Sandhills State Park one night and went hunting for scorpions. I had never seen a scorpion before, and I had no idea they fluoresced! The little ones we saw glowed a bright green under the black light. So, I decided to get this little guy at the gift shop to remember it.
Both cephalopods and arthropods have been around since the Cambrian, so are of particular interest to paleontologists. Today, most people would recognize cephalopods as octopuses, squid, and cuttlefish, and arthropods as insects, arachnids, and crustaceans.
During the Ordovician, around 480 million years ago, the most famously known cephalopods were the nautiloids:
And of course the arthropod everyone knows and loves, the trilobite: