Exceptionally preserved caddisfly larval cases (Insecta) from the lower Cretaceous of the Liupanshan basin, Western China

Abstract

Abundant well-preserved tubular fossils of caddisfly (Insecta: Trichoptera) larval cases are reported from the Early Cretaceous Madongshan and Naijiahe formations of the Liupanshan Basin, Ningxia Province, western China. Most cases were mainly preserved in life position and densely packed in various layers. Individual cases in each layer tended to be same in size and were erect and parallel to one another and open at both ends. In a transverse section cut perpendicular to the long axis of the cases, individual case appears to form a rounded ring. Small cases are elliptic in a cross-section oblique to the long axis of the cases. Tube walls are nearly subparallel to one another in longitudinal section with both ends being open. The caudal end of the case slightly tapers and usually points downward. The cases were closely packed, almost touching with one another and lacking bifurcate or connecting structure. The overwhelming majority of cases were partially or fully filled with calcite. The case wall embraces a medium particle layer flanked by inner and outer organic layers. Individual particles are ovate in outline and comprise cryptocrystalline or ganic pellets. SEM imaging shows that those pellets are sub-cylindrical in outline and elliptic in cross section, and are made primarily of calcium carbonate. All features observed justify the assignment of the Liupanshan caddisfly cases to ichnogenus Coprindusia. The extinct insect Ningxiapsyche fangi was found in association with the Liupanshan caddisfly larval cases, and thus could be the candidate of the potential trace-maker.