The Peninj mandible is a nearly complete lower jaw from a male Paranthropus boisei. Note the combination of megadont cheek teeth and the relatively small incisor teeth, which reflect the adaptations of Paranthropus boisei towards heavy chewing (grinding of tough, fibrous foods). Note as well the buttressing of the jaw, visible in the bottom photograph as a thickening of the bone at the molars where the ascending ramus converges with the corpus of the mandible (if you need help with these terms go to the skull lesson). This buttress is a structural adaptation to help the jaw withstand the pressure applied to it by the powerful chewing muscles.