Eyes Wide Open...500 million years ago.

What do most people think of when they here the word "prehistoric?" Giant dinosaurs and pterodactyls patrolling ancient steaming jungles. Cavemen hunting giant woolly mammoths over frozen solid tundra? How about the trilobites, one of the oldest animals on Earth and one of the most popular options for budding fossil collectors.

Trilobites first appeared about 525 million years ago in the shallow warm seas of the Early Cambrian period, when life on Earth was just starting to get a grip on evolutionary compitition. New animals were appearing in the sea...some ferocious crab-like predators - EEEEK!!! - which were hungry for tasty creatures crawling around on the seabed.

Many animals including trilobites developed hard calcitic shells, which protected their skins (pun intended) and made excellent fossils - TAKE THAT FRAGILE DINOSAUR BONES!!! Trilobites were related to modern day lobsters, spiders, and horseshoe crabs. Some species of trilobites were so numerous, that sometimes their fossils can be found in the billions at a single place - talk about a crowd!

The real milestone of the trilobites were their eyes. Trilobites were some of the first animals on Earth to have complex eyes, possibly eyes of any kind. So why did they need eyes? Remember the crab-like predators of the Cambrian? They also developed jaws powerful enough to crush the shells of trilobites. To prevent attack, many trilobites developed complex vision to detect predators in the sunlit seas. They eyes were compound, made up of thousands of tiny lenses, each processing light.

Eyes became especially useful around 485 million years ago during the Ordovician period. Why? During the Cambrian, a new type of animal appeared. It had a central backbone, a tiny mouth slit, gills, and primitive fins. This tiny animal was the first fish. About 485 million years ago, they had developed jaws and had evolved into the first sharks and armored fish. There were also giant nautiloids and sea scorpions hunting about and trilobites had to be especially careful to not get eaten.

A giant armored fish of the Paleozoic

Many trilobites also developed long spines and spikes to protect themselves from being a Paleozoic lunch bag. I sure would not want to eat my sandwich if it was covered in sharp spikes, now would I. Trilobites shells were also jointed, meaning that they could easily roll up to protect themselves into a ball.

A spiny trilobite

However curling up and hunkering down on the seabed did squat to protect them from freezing seas 450 million years ago and supervolcanic eruptions 250 million years ago. These two events are now why we only see our trilobite friends petrified in the rock or in a prehistoric museum diorama.