Gyraulus is a genus of small, mostly air-breathing, freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails. The genus Gyraulus is known from the Early Cretaceous to the present. Fossils attributed to Gyraulus sp. have been found in the lakebottom sediments of the Yixian Formation in China, dating to 125 million years ago. The minute species Gyraulus crista, although technically a pulmonate gastropod, does not use air for respiration, but instead has a mantle cavity which has much water.