[citation needed] In the past decades, many different hypotheses were made on the possible function of the postorbital bar.
Greaves suggests that the bar strengthens the relatively weak orbital area against torsional loading, imposed by bite force in species with large masseter and temporalis muscles.
[9][10] Cartmill[7][11][12] suggests that in small mammals with large eyes and relatively small temporal fossae, where the anterior temporal muscle and the temporalis fascia are pulled to a more lateral position with increasing orbital convergence (front-facing eyes), the tension caused by the contraction of these muscles would distort the orbital margins and disrupt oculomotor precision.
Without a stiffened lateral orbit, deformation would displace soft tissues, when contraction of the anterior temporalis muscle takes place, thus impeding eye movement.
Well-developed postorbital processes have evolved separately within the orders of the Dermoptera and Hyracoidae and the Chiropteran families of Emballonuridae and Pteropodidae and to varying degrees within many carnivorian taxa.