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Paranthropus boisei: OH 5

  • Common Name:

    Nutcraker Man

  • Geologic Age:

    1.8 Ma

  • Discovery Date:

    17 Jul 1959

  • Discovered By:

    Mary Leakey

  • Discovery Location:

    Olduvai Gorge, Tanzania

  • Cranial Capacity:

    530 cc

  • Specimen Age:

    Young adult

  • Sex:


  • Estimated Weight:

    70 kg

    The OH 5 cranium displays classic Paranthropus anatomy such as "hyper robust" cranial morphologies, and has been used to informed inferences about the taxonomic assignments of later P. boisei skulls.

    Among the more notable characters exhibited on OH 5 are laterally flaring zygomatic arches, a broad concave face, and highly specialized craniofacial configurations that suggest a powerful chewing apparatus. With its prominent sagittal crest (that acts as an anchor for the heavy temporalis muscles) and enormous premolars and molars (known as megadontia), OH 5 had a powerful and extremely efficient chewing apparatus that utilized remarkable vertical force during mastication.

    Concerning dentition, the incisors and canines of OH 5 are relatively small compared to the premolars and molars; coupled with the massive cheek teeth, this implies that P. boisei did not heavily rely on slicing and piercing during mastication. Rather, the specialized dentition suggests that OH 5's diet included more on tough, abrasive vegetal foods.

    Other distinct morphologies present in OH 5 consist of a retracted palate, laterally sloping supraorbital tori, and a pronounced sagittal crest that is relatively more anteriorly positioned on the cranium. The face exhibits relatively reduced prognatism.

    While debate persists concerning the phylogenetic origin of Paranthropus, the extremely specialized and robust cranial morphologies, in addition to the highly derived dentition specializations tend to exclude P. boisei, and its robust counterparts, from being ancestral species to Homo sapiens.

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