Form, Function, and Architecture of Ostracode Shells

Ostracodes are microscopic crustaceans that live on the sea bottom, in lakes, ponds, and estuaries, and are frequently found as fossils in sedi­ mentary rocks ranging in age from the Cambrian to the present. They are improbable animals, at least in their appearance, which invaded a world too small for most of the organ machinery developed by their ancestors. So far as we know no other animal ever evolved from the ostracode. Nevertheless, in its struggle to survive, thousands of different species of ostracodes evolved to mark geologic history with attempts to develop suitable designs to fit the needs of environmental change. A handful of sand or a piece of drill core taken from the sea or ocean floor may have hundreds of specimens of ostracode shells. Some ostracodologists (there are three or four hundred in the world) study these curious fossil remains for very practical reasons. While some are interested in dating rocks, especially pre-Cretaceous strata, others may be assisting other micropaleontologists to reconstruct the ecological conditions of past environments. They consider the design of each species to be uniquely adapted to the time and circumstances of its origin. The problem has been to develop a body of theory to explain how this occurs. For many years the best that could be hoped for was to correlate species, with unique taxonomic characters or traits, with other similar ones where the age was known or the environment could be inferred from accom­ panying geologic data. Many of these characters were based on form analogy without knowledge offunctional structure. A few ostracodologists (Liebau 1977, Benson 1972, 1974, 1975, Peypouquet 1977), risking the dangers of strained and mistaken analogy, set out in search of a set of