There have been very few published reports of stromatoporoids and colonial corals with borings that contain linguloid brachiopods; all are from the Ordovician and/or Silurian in just four areas of eastern Canada and northwestern Europe. Here, we report the discovery of an earlier Ordovician occurrence, in both stromatoporoids and corals, and expand the geographic range of such associations to central Canada. In the Upper Ordovician Selkirk Member of the Red River Formation, southern Manitoba, the stromatoporoid Stratodictyon and tabulate coral Protrochiscolithus commonly contain cylindrical macroborings representing the ichnogenus Trypanites, almost certainly produced by worms. In a few specimens, a small proportion of borings contain single linguloids. The linguloids occur predominantly in borings with relatively large diameters, but their occurrence with respect to boring length and their vertical location within borings are random. They are interpreted as nestlers that occupied vacant
borings throughout life. Although some of the borings were covered over by subsequent growth of the host or recolonization of its surface, there is no evidence of embedment structures in stromatoporoids or corals that would indicate interaction of the host with either the borers or linguloids.This is comparable to occurrences in the Ordovician of Manitoulin and Anticosti islands in eastern Canada, in that the linguloids are found within Trypanites borings without associated embedment structures. In the Silurian of Anticosti, Gotland, and the Welsh Borderlands, however, some borings were further developed into embedment structures during upward growth of the hosts, indicating that these relationships involved some type of symbiosis.