and three molars in each half of the jaw for both jaws. The canines, due to a lack of honing facets (which keep them sharp) and their overall stoutness, have been suggested to have functioned like premolars and molars (cheek teeth). Like other apes with enlarged molars, the incisors of Gigantopithecus are reduced. Wearing on the tongue-side of the incisors (the lingual face), which can extend as far down as the tooth root, suggests an underbite. Overall mandibular anatomy and tooth wearing suggests a side-to-side movement of the jaw while chewing (lateral excursion). The incisors and canines have extremely long tooth roots, at least double the length of the tooth crown (the visible part of the tooth). These teeth were closely packed together. In the upper jaw, the first premolar (P3) averages in surface area, the second premolar (P4) , the first and/or second molars (M1/2, which are difficult to distinguish) , and the third molar (M3) . In the lower jaw, P3 averages , P4 , M1/2 , and M3 . The molars are the biggest of any known ape. Teeth continually evolved to become larger and larger. The premolars are high-crowned, and the lower have two tooth roots, whereas the upper have three. The lower molars are low-crowned, long and narrow, and waist at the midline—which is more pronounced in the lower molars—with low-lying and bulbous cusps and rounded-off crests. The tooth enamel on the molars is in absolute measure the thickest of any known ape, averaging in three different molars, and over on the tongue-side (lingual) cusps of an upper molar. This has attracted comparisons with the extinct Paranthropus hominins, which had extremely large molars and thick enamel for their size. However, in relation to the tooth's size, enamel thickness for Gigantopithecus overlaps with that of several other living and extinct apes. Like orangutans and potentially all pongines (though unlike African apes) the Gigantopithecus molar had a large and flat (tabular) grinding surface, with an even enamel coating, and short dentine horns (the areas of the dentine layer which project upwards into the top enamel layer). The molars are the most hypsodont (where the enamel extends beyond the gums) of any ape. Palaeobiology Diet Gigantopithecus is considered to have been a herbivore. Carbon-13 isotope analysis suggests consumption of C3 plants, such as fruits, leaves, and other forest plants. The robust mandible of Gigantopithecus indicates it was capable