Q What are the muscles of mastication?
A: Temporalis
Masseter
Medial and lateral pterygoid
Q What is the synapsid opening
A The opening formed by the zygomatic arch, which the temporalis passes through.
Q What is a synapsid
A: Some classify synapsids as premamalian reptiles, an important step in the evolution to mammals.
Reference:
http://www.amnh.org/our-research/paleontology/collections/fossil-amphibians-reptiles-and-birds/
https://www.researchgate.net/publication/13773726_Paleontology_of_the_temporal_fossa