Endolithic trace fossils in Ordovician-Silurian corals and stromatoporoids, Anticosti Island, eastern Canada

Bioerosion was a significant process in the destruction of reef-building skeletons in early and mid-Paleozoic marine carbonate settings. Ordovician-Silurian corals and stromatoporoids from Anticosti Island show a limited diversity of macroborings, dominated by Trypanites, but also includes rare occurrences of an Ordovician bivalve boring (Petroxestes pera), described here for the first time in Early Silurian stromatoporoids. Two problematic embedment structures, one containing lingulid brachiopods, resemble borings but did not contribute to bioerosion. The distribution of the embedment structures and Petroxestes pera are restricted by facies and skeletal substrate. Trypanites is relatively nonspecific, occurring in reef and off-reef facies and in most skeletal substrates; it does not appear to have been affected by the Late Ordovician mass extinction.