Mexican Clam Shrimp (Cyzicus mexicanus) is a medium-sized (up to 8 mm) freshwater branchiopod that is widespread through the Great Plains of Canada and the U.S., and southwest into central Mexico. In New Mexico they occur in the Rio Grande and Pecos river basins. They inhabit temporary wetlands, pools, and playas. Eggs are able to survive periods of drying and will continue their development when re-wetted.