Like other members of the Paranthropus genus, P. boisei is characterized by a specialized skull with adaptations for heavy chewing. A strong sagittal crest on the midline of the top of the skull anchored the large chewing muscles (temporalis muscles) from the top and side of the braincase to the lower jaw, and thus moved the massive jaw up and down. The force was focused on the large back teeth (molars and premolars). Flaring cheekbones gave P. boisei a very wide and dish-shaped face, creating a larger opening for bigger jaw muscles to pass through and support massive cheek teeth four times the size of a modern humans. This species had even larger cheek teeth than P. robustus, a flatter, bigger-brained skull than P. aethiopicus, and the thickest dental enamel of any known early human. Cranial capacity in this species suggests a slight rise in brain size (about 100 cc in 1 million years) independent of brain enlargement in the genus Homo.
Oh, I get it now.