Short chains of discoidal, rarely spheroidal, structures, recovered by acid maceration of Lower Devonian (Lochkovian) siltstones from the Welsh Borderland are interpreted as coprolites because they comprise comminuted or homogenized tissues. They are placed in a new species of the ichnogenus Lancifaex. Tissues include the smooth and banded tubes of Nematasketum, a close ally of Prototaxites, and rarer cuticles of Nematothallus and Cosmochlaina. All these taxa have been assigned to an extinct class, Nematophytales Lang 1937, which Lang thought was intermediate between higher plants and algae. More recently, there is more compelling evidence, particularly from Prototaxites, that the class had fungal affinities. We thus conclude that the producers of the coprolites were selective feeders on nematophytes, and hence on fungi. Prior evidence for the reconstruction of terrestrial ecosystems in the mid-Paleozoic has been dominated by mega- and mesofossils of primary producers because body fossil records of consumers, whether carnivores, herbivores, or detritivores, are rare. Coprolites previously described from the locality that contain spores and residues of higher plants provide indirect evidence, based on consideration of comparative body size of coeval animals recorded elsewhere, for detritivory, probably in millipedes. In a similar approach involving mites, collembolans and millipedes—animals known to be mycophagous today—it is concluded that millipedes were the most likely producers of the coprolites described here.