As Diictodon infants grew up, their skulls not only got larger but also changed shape depending on their gender. Up to 5cm skull length, none of the Diictodon skull shows tusks. From 5-15 cm skull length, roughly half of the Diictodon specimens have visible canine tusks the others just have a bony projection called caniniform process The tusks were therefore mainly used as visible display of the male Diictodon's prowess and fitness when competing for mates within the community