US Outdoor Store has an interesting line of protective sunglasses which are fashionable, attractive, practical and rugged; able to resist hard treatment, these sunglasses from various brands can be used on almost any outdoor adventure.

In order to review information about the company that distributes this product, shipping policies and general issues concerning these products please click here.

And speaking of eyes, this makes us remember about the trilobites, a very extensive family of arthropods, distantly related to the shrimps and insects of today; these animals liven on Earth even before the dawn of the age of dinosaurs. Trilobites had segmented bodies, protected by an external skeleton much similar to what we see in all sorts of modern arthropods (insects, by the way, are arthropods); this shell acted in many cases as their personal armour, protecting their bodies from the bites of all sorts of predators of strange forms that existed in the distant past.

There were scores of trilobite species, all marine; they appeared during the Cambrian period, which went from 570 to 505 million years ago, and vanished into extinction during the Permian, between 285 and 245 million years ago, just before dinosaurs began to appear on Earth.Trilobites could measure between a few millimetres and about 60 centimetres; there were many variants in their body shape, but all retaining some basic characteristics. Some trilobites lost their vision due to evolutionary needs related to very specific environments, like great oceanic depths or live in underwater, dark caves.

However, others always called our attention because of the development of their eyes. Their field of vision was difficult for us to understand: some species had 360 degree vision, both horizontally as well as vertically, at the same time. It means that these animals had spherical vision, enabling them to see in all directions at the same time: forwards, backwards, down and upside.

Most likely, this was a defensive adaptation to detect any approaching predator; combining this sensorial adaptation with good swimming capabilities, these trilobites would have become quite difficult to catch. And another curios thing is that some trilobite eyes have reached our days fossilised in silica, which is a transparent mineral; using small cameras and endoscopes, it was possible to run some tests in these composite eyes, similar to those of today's insects, and see what was it like to see thorough the eyes.

We saw pictures of 'Happy buttons' as seen thorough the eyes of a fossil trilobite. Regrettably, there are no more trilobites; for all accounts, they have gone extinct during what was probably the largest environmental catastrophe of the world's history, at the end of the Permian. Not much is known about this event, but it was certainly bigger and deadlier that what killed the dinosaurs many millions of years afterwards.

Similar products

Articles

Similar Sites

Books

Forum