W – Width of the braincase: Position 3 rulers as shown in the photographs below. Rulers 1 and 2 should stand perpendicular to the table and flat against the skull (imagine 2 rulers flat against where the ears would be positioned). Position ruler 3 resting on the top of the skull, making sure that it is parallel with the table. Read the distance between rulers 1 and 2 in mm. Record your data in the first column labeled “W”.
Skull width measurement for two different species with the three rulers perpendicular to each other. Note the placement of the upright rulers on the sides: for the species on the right photograph, the rulers are not at the widest point of the skull (the ‘zygomatic arch’ or cheek bone), but at the widest point of the braincase further back.
Next you will assess the approximate shape of each cranium: