that covered areas of the earth that today are land masses. Mosttrilobites were bottom dwellers, although some may have been swimmers or floaters.Some that possessed exceptionally large eyes and a large field of vision, such asCarolinites, are thought to have been swimmers that inhabited surface waters. Others,with reduced eyes or no eyes at all, preferred deeper, darker waters. Many trilobites, suchas Olenellus, burrowed into the sea bottom for protection and to seek food. Trilobitesemployed a variety of feeding strategies. Many plowed through mud at the bottom ofoceans and seas, ingesting the sediment to sort out organic matter. Others werescavengers or predators. Most trilobites could roll themselves up into a defensive positionso that only the exoskeleton was exposed. Growth of trilobites involved a process ofmolting caused by the growth of the body within the exoskeleton becoming too large to becontained. With the hard exoskeleton being shed periodically and a larger new one beingdeveloped. After each molting the trilobite was only covered by a flexible, chitinous shellwhich gradually mineralized and hardened. It has been recognized that some Trilobites evolved elaborate spiny forms duringthe Devonian era. It was thought at one time that this spinuosity was a development forplanktonic life, in an aid to prevent the animal from sinking deeper in the water column butmost trilobites were too large for these spines to function in that way, so it is more likelythat they were used for protection. The majority of trilobites had a smoother exterior earlyin the Cambrian System, but during the Silurian/Devonian several species developed spinesand bumps. In the image to the left is an example of spine development, here the elongatedpleural spines of Kettneraspis willanisi can be seen clearly (It is 3/4" in length). Anotherfunction of the spike development could have been to spread their weight, preventingthem sinking into the sediment of the ...
