Orangutan-Human Characters -- Incisive Foramen

In mammals and monkeys, and gibbons there are two anterior palatine fenestrae or holes that provide entry to the palate by the left and right greater palatine nerve and nasopalatine nerves respectively (see gibbon top left).

In the Great Apes these holes are closed immediately above, but there are still two openings to the palate in the gorilla and chimpanzee although in the latter they are positioned very close together.

The human and orangutan are unique in having a single opening or incisive foramen, with the orangutan having the most derived condition where the foramen is reduced to a narrow slit. (Schwartz, 1983, 1988b, p. 171).

Groves (1987: 539) states the human and orangutan condition to be correct.

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