Neopentadactyla mixta (Östergren, 1898) A micro-CT scan visualizing the position of the calcareous ring B lateral view with micro-CT imaging of the anterior part of the calcareous ring (AR: most anterior radial piece; AIR: most anterior interradial pieces; SAR: subsequent anterior radial pieces; SAIR: subsequent interradial anterior pieces; Mesh: meshwork of radial and interradial median to distal pieces) C oblique view with micro-CT imaging showing a guttered internal side of the calcareous ring D focus-stacked view of the calcareous ring and associated structures (T: tentacles; LM: longitudinal muscle with bifurcation point (BfP); PV: Polian vesicle: SC: stone canal). Scale bars: 1 cm (A–D).