Origin of the pterygoid bones and pharyngeal musculature in mammals

Living reptiles lack pharyngeal muscles. This was probably also true for primitive synapsids, or "mammal-like reptiles," as well. On the other hand, mammals possess a complex array of pharyngeal muscles that play an important role in feeding.  Suckling and the control of airflow to and from the lungs are prerequisites for endothermy. In order speculate on the progressive addition of pharyngeal muscles in the phylogenetic line leading to mammals, the challenge is to to identify osteological features that can be associated with the pharyngeal muscles.