The crab fossil record extends to the Early Jurassic epoch, more than 200 million years ago. Fossils of nonmarine crabs are sparse, until now with the discovery of Cretapsara athanata, a previously unknown true crab preserved in Cretaceous amber from Myanmar. The 5-mm-long crab is the oldest and the most complete fossil crab found. Well-developed gills indicate an aquatic to semi-aquatic crab.
Previous fossil records of crabs suggested that crabs ventured onto land and adapted to freshwater about 75 to 50 million years ago. This crab most likely died in brackish or freshwater near the coast or an estuary. This demonstrates that crabs became terrestrial about 100 mya — much earlier than previously thought.