The presence of a small colony of Synastrea bellula (d’Orbigny, 1850) in Berriasian beds of the pelagic Maiolica in the Venetian Prealps (NE Italy) provides a key for interpreting the palaeobathymetry of the formation on the Trento Plateau. This pennular scleractinian belongs to a zooxanthellate group whose fossil and modern representatives are characterized by an outstanding specialization in colonizing deeper parts of the marine photic zone (mesophotic zone). The coral grew on the shell of an inferred ammonoid affected by intense microbial erosion. The conch was encrusted first by bryozoans and later by the coral, which immurated a microserpulid, designated as Turriserpula coralliophila gen. et sp. nov. Applying the sclerochronology method, a life duration of the stony coral of at least twelve years is inferred.