A single specimen of the large Silurian gastropod Phanerotrema sp. from the Goéland Member on Anticosti Island preserves an outstanding microcosm of its surrounding community, including multiple trophic groups, strategies for niche partitioning, and innovative adaptations for survival in a mud-dominated marine ecosystem. At least seven associations are recorded in this fossil specimen, including the gastropod itself, healed breakage from an apparently failed attempt at durophagous predation, domichnial bioerosion, encrustation by a stromatoporoid, nestling behaviour and commensal embedment by a lingulid brachiopod, and epifaunal attachment by two cornulitids. As a benthic island, the gastropod conch provided a favourable isolated habitat for hard substrate colonizers. This unique specimen sheds light on the broader Paleozoic ecosystem, including the potential importance of benthic islands in the evolution of niche-partitioning strategies in space-limited communities.