Presence of an obturator groove in some Cercopithecoids and small-sized Platyrrhines

The presence of the obturator groove in the atelines and the hominoids is thought to be caused by the pressure of the active muscle obturator externus against the femoral neck during extension of the hip. However, the presence of an obturator groove is common in same Cercopithecoids and Platyrrhines who rarely extend the hip during their usual posture and locomotion. The functional significance of this groove is called into question, especially in some Cercopithecoids, with reference to a hip dissection of Macaca. It is suggested that the presence of the groove can also indicate a hip frequently flexed.