Complex sentence: All extant Feliforms have auditory bullae (bony capsules enclosing the middle and inner ear), which are double-chambered--composed of two bones joined by a septum.
Split into simpler sentences: All extant Feliforms share a common attribute: their auditory bullae (bony capsules enclosing the middle and inner ear). In all extant Feliforms the auditory bullae are double-chambered, composed of two bones joined by a septum.