Novel trace fossils of non-marine annelids from the Upper Cretaceous Wapiti Formation, Canada, and their paleoecological implications

Despite the important ecological roles played by non-leech clitellates (”oligochaetes”), studies pertaining to the ichnology of these animals are scarce. Part of the problem is due to the lack of diagnostic trace fossils that can be confidently attributed to worms. Here, we report on well-preserved coprolites and radiating burrows of probable worm origin from the fluvial Wapiti Formation (late Campanian–early Maastrichtian) of Alberta, Canada. To characterize these trace fossils, they are described in detail and compared with other trace fossils and modern traces. The coprolites and burrows show distinctive features not encountered in previously described trace fossils. The coprolites form arc-shaped or conical mounds and we propose Cumulusichnus arciformis isp. nov. and Cumulusichnus wapitiensis isp. nov. to describe the two forms. The two ichnospecies of Cumulusichnus from the Wapiti Formation are interpreted to have been produced by freshwater oligochaetes. The burrows form radiating sets that each occur at the base of a vertical shaft, and the burrows are architecturally similar to Clematisichnia in being unbranched and subhorizontal with annulated walls. These burrows bear some resemblance to traces produced by modern anecic earthworms. These trace fossils provide valuable insights into the roles played by ancient annelids in wetlands. This study identifies some potential directions for future research on traces and trace fossils of vermiform organisms.