The Mont-des-Récollets section (N France): a key site for the Ypresian-Lutetian transition at mid-latitudes - reassessment of the boundary criterion for the base- Lutetian GSSP Author Steurbaut, Etienne Royal Belgian Institute of Natural Sciences, OD Earth and History of Life, Vautierstraat 29, B- 1000 Brussel (Belgium) and Department of Earth, and Environmental Sciences, KU Leuven, Celestijnenlaan 200 E, B- 3001 Leuven (Belgium) etienne.steurbaut@naturalsciences.be Author Nolf, Dirk Royal Belgian Institute of Natural Sciences, OD Earth and History of Life, Vautierstraat 29, B- 1000 Brussel (Belgium) text Geodiversitas 2021 2021-05-25 43 11 311 363 journal article 10.5252/geodiversitas2021v43a11 fc56a00d-cf6b-4fda-aa56-d0492e4781cb 1638-9395 4891107 urn:lsid:zoobank.org:pub:07D1F5A8-98E2-40F1-A716-D25CB975EA4C Toweius brusselensis Steurbaut, 2011 ( Fig. 19 K-N) Toweius brusselensis Steurbaut, 2011 : figs 15-16; pl. 1, figs 20-22. DISTRIBUTION. — This species is known from several boreholes (e.g. Knokke, Vlakte van de Raan) and outcrops (e.g. Gobertange, Nederokkerzeel, Vossem) in Belgium , where it ranges from the middle of the Brussel Sand Formation (middle part of Unit B3) up to the basal part of the overlying Lede Sand Formation. In Belgium its range seems to extend from lower middle NP14 to the base of NP15. Some rare small-sized specimens have been identified in the ‘Chaumont-en-Vexin sands‘ and the ‘Glauconie Grossière s.s.’ of the Paris Basin (base NP14). Occurrences outside Europe are scarce and up to now restricted to the Aktulagay section in Kazakhstan (a few specimens in uppermost NP13, Steurbaut 2011 ). DISCUSSION This taxon is represented by relatively small forms (d = c. 5 µm ) in the early part of its range (e.g. middle of Unit B 3 at Vossem; Fig. 19M, N ). Late forms from the upper part of the Brussel Sand Formation reach up to 8 µm in length ( Fig. 19K ).