Ulnaria menyuanensis sp. nov., internal view, SEM A a valve with associated valvocopula B middle part detail from A, note serrated projections (three arrows) C, D apical details from A, note serrated projections (C, three arrows) and closing plates (D, two arrows) E, F details from other apex from A, note serrated projections (E, three arrows) and closing plates (F, two arrows). Scale bars: 10 μm (A); 5 μm (B, C, E); 2 μm (D, F).