Polygonal surface model of A Eurhinoceros sondaicus skull (in yellow) and B Rhinoceros unicornis skull (in blue) with measured angles. Abbreviations: Iscp–angle between plane spanned between the lateral semicircular canals (LSC) of both inner ears and the palatal plane; o–angle of the occipital crest between the occipital plane and the parietal plane; po–angle between occipital plane and palatal plane. Skull drawings and colours have been maintained from the original. Adapted with permission from Schellhorn (2018: 53).