My set of Netter's Anatomy flashcards from medical school a decade ago describe the functions of the deep fibers of masseter (the 2nd layer of the masseter muscle) as 'retracting' the mandible. Interestingly the cards also say -here I interpret as regarding the superficial layer of masseter - that "some of its fibers may protrude the mandible" (which makes sense if you look at the diagram).
What is lost in translation or reinterpretation in the quote you've posted is that retracting the mandible is either the function of the deep layer of masseter or instead the function of this newly discovered third 'coronoid' layer (or quite possibly, both); it is not as though anatomists thought 'how the jaw retracts' to be unanswered before today, but rather it seems they have been using an incorrect or perhaps incomplete picture.
Interestingly I can see the stark difference in depiction between Netter's diagram illustrating deep masseter [1] and this other one.[2]
I also note the description from Netters, which states that part of Masseter inserts on "the lateral surface of the coronoid process", describes pretty well the muscle being announced in this paper, as per their photographs.
What is lost in translation or reinterpretation in the quote you've posted is that retracting the mandible is either the function of the deep layer of masseter or instead the function of this newly discovered third 'coronoid' layer (or quite possibly, both); it is not as though anatomists thought 'how the jaw retracts' to be unanswered before today, but rather it seems they have been using an incorrect or perhaps incomplete picture.
Interestingly I can see the stark difference in depiction between Netter's diagram illustrating deep masseter [1] and this other one.[2]
I also note the description from Netters, which states that part of Masseter inserts on "the lateral surface of the coronoid process", describes pretty well the muscle being announced in this paper, as per their photographs.
[1] https://ranzcrpart1.fandom.com/wiki/Temporal_fossa:Masseter_...
[2] https://www.medspine.es/wp-content/uploads/2017/02/Sin-t%C3%...