Arthropods are the most abundant and diverse group of animals in the history of life on Earth.  While the Palaeozoic arthropods diversified and proliferated in ocean waters (in which modern representatives of the group still thrive), some strands evolved from the marine ancestry to play a vital role in the ­colonization of fresh waters and terrestrial environments in Mid-Palaeozoic times.  Furthermore, the non-marine arthropods, in the form of the insects, were the first animals to conquer the airways.  The non-marine arthropod group as a whole co-evolved with plants through several evolutionary developments, involving such processes as the formation of soils and pollin­ation.  Even from an anthropo­centric point of view, they still are one of the most important groups today because of their role in the pollination of flowering plants and as ­vectors of diseases.  Consequently, the evolutionary history of the group is of ­considerable interest and importance.  But many aspects of this history are under-represented in the fossil record because of problems with preservational potential and bias in their stratigraphical and collecting record.
 
Recent decades have seen a much better understanding of how arthropods are recruited to the rock record, with the result that ancient deposits with the greatest preservation potential for fossil arthropods have been searched with success.