Cualac

Endemic to a handful of natural springs in the Río Verde valley, San Luis Potosí state, Central Mexico. The valley is believed to have once been filled by a large lake and the relict springs are part of the elevated Río (river) Verde basin which later drains into the much larger Río Pánuco system. Much of the aquatic fauna found in the valley is endemic to the area but in many cases threatened by introduced species.