Fossil Information Sheet F006
One of the most numerous and successful marine organisms of the early Paleozoic era (appx 450 million years ago) specifically the Cambrian period, flourishing for close to 300 million years.
They ranged in size from a few millimeters to 90cms (appx 3ft.)
They appear similar in shape to living forms such as the wood lice but are from the same family as shrimps, lobsters, crayfish etc., all Arthropodia.
Like most arthropods they could only grow by shedding their old skins and many fossils are actually the shed external skeletons.
They had many legs each with a set of gills and most had sophisticated multi-faceted eyes.
The name is derived from the three lobes into which the body segment is divided, the head, thorax and posterior section or Pygidium (tail).
Most fossilised Trilobites found lived in shallow ocean waters and on reefs.
Trilobite tracks show a wide variety of activities and some of the spiny Trilobites may have been capable of swimming.
Their skeletons are found in all types of sedimentary rocks from limestones to shales.
More than 1,500 species are known and many more yet to be described.
Sites where they have been found include the Atlas Mountains, Morocco, parts of Northwest Scotland, Illinois USA, Utah and Virginia USA, Oklahoma, and British Columbia.
The legs of the Trilobite were softer than the exoskeleton and as such did not tend to preserve as well.
Though there have been a few specimens that showed legs and also some antennae in Burgess Shale in Canada and Chengjiang in China.
The example from my stock list (illustrated at the top of this sheet) is a very good example exhibiting fine detail, particularly the head, and is from the Atlas Mountain range in Morocco.