Twenty years ago, a unique and highly diverse subterranean group of animals was discovered on the Yilgarn plateau. They live in hundreds of groundwater 'islands' - within thin limestone formations known as calcretes that formed by precipitation from groundwater along ancient drainage channels. The entire northern Yilgarn region 'resembles a subterranean archipelago' with more than 200 major calcrete bodies and hundreds of smaller ones, which are separated from each other by fine alluvial deposits.
The animals living in these calcretes include water beetles, many types of crustaceans (such as amphipods, copepods, ostracods, oniscids), worms, mites, centipedes and springtails. Only a small proportion of these calcrete animals have been identified. A 2010 study using DNA barcoding to distinguish species found at least a dozen in a single calcrete, which suggests the diversity of species is even 'richer than previously anticipated'.