To date, the two highest units (Nekum and Meerssen members) of the Maastricht Formation in the Maastrichtian type area (southeast Netherlands, northeast Belgium) have yielded some twenty ammonite species, the majority of which are heteromorph. Baculitids and scaphitids predominate, while diplomoceratines and nostoceratids are extremely rare and do not appear to range higher than the basal portion (subunit IVf-1) of the Meerssen Member. From subunits IVf-5 and IVf-6 of that unit as exposed at the quarries of ENCI-Heidelberg Cement Group (Maastricht) and Ankerpoort-Curfs (Geulhem), two specimens of the polyptychoceratine Phylloptychoceras cf. sipho have recently been collected, from an interval a few metres below the Cretaceous/Paleogene (K/Pg) boundary. Elsewhere in Europe, Ph. sipho has previously been recorded from the uppermost Maastrichtian of Denmark and the lower upper Maastrichtian of the Bay of Biscay sections (France, Spain).