Body fossils or trace fossils: a reinterpretation of mayfly larvae body impressions from the Upper Cretaceous Wapiti Formation, Alberta, Canada

In this study, we present a revised interpretation of mayfly larval body impressions previously described from the fluvial Wapiti Formation of Alberta, Canada. Unlike typical insect fossils that occur in lacustrine deposits or amber inclusions, these fossils are interpreted to have been preserved in a depositional setting characterized by currents rapid enough to erode and transport fine-grained sand. To determine how the fossils were formed, we examined the spatial relationship between the fossils and associated tool marks preserved on the same bedding surface. All 16 of the fossil specimens analyzed were in life orientation with their heads directed upstream, suggesting that the impressions were produced by live organisms. Here we propose a new ichnotaxon Kalyptichnus belli n. igen. n. isp. for shallow self-burial traces of insect larvae.