Serpulid tubeworms (Annelida, Polychaeta) and a vermetid gastropod from the Late Oligocene of Denmark.

The serpulid palaeocommunity of the Late Oligocene Brejning Formation in Jylland (Jutland) is described and discussed based on specimens collected at Vilsund, Mogenstrup, Hinge, Aarhus, and Nørre Vissing localities. The serpulid species are: Protula cf. septaria (Giebel, 1858), Filogranula mogenstrupensis sp. nov., Placostegus vilsundensis sp. nov., Placostegus cf. erectus (Nielsen, 1931), and Placostegus cf. bilobatus (von Koenen, 1891). The semi-ordered irregularly oriented prismatic microstructure (SOIOP) of the tube wall of Protula cf. septaria (Giebel, 1858) is examined and discussed for the first time. These serpulids lived in a calm, normal marine palaeoenvironment below storm wave base. Furthermore, the first known vermetid gastropod from the Late Oligocene of Jylland, Vermetus jyllandensis sp. nov., is introduced, and its shell microstructure is discussed.