Microbial-caddisfly bioherms in the Early Cretaceous Yixian Formation in the Yixian Basin, Western Liaoning, China

Microbial-caddisfly bioherms have recently been discovered in the Early Cretaceous Yixian Formation in Western Liaoning, China. They consist of thousands of aggregated caddisfly larval cases that are generally vertically oriented and parallel to each other. These cases are similar in size, 12-14 mm long with an inside diameter of 2 mm and an outside diameter of 3-4 mm. Three kinds of particles were principally identified occurring on the case surface and were used as the basis for dividing them into three types. In addition to biohermal cases, there are single caddisfly cases that are widely distributed in the Yixian Basin. Nevertheless, the identity of the environmental conditions responsible for fabrication is difficult to establish. An analysis of microbial-caddisfly bioherms globally revealed that their formation occurs under dry conditions within warm-temperate to xeric climates.