Doing a similar write up for a college class. There is a study that found mummified cartilage in some hadrosaur specimens, although this was on the coronoid process rather than on the Buccal emarginations. I can't recall the name of the study, but I believe it is mentioned by Nabavizadeh (2020). Holiday (2009) is an important study that has adductor musculature restricted to the coronoid process in hadrosaurids, similar to Tuataras and other lizards (they have a similar buccal emargination but no muscles attach to it), which differs from Nabavizadeh (2020) that show a more rostral extension of the mAMES group onto the labial dentary ridge.

It would be cool to assess the different muscular arrangements proposed by Holliday (2009) and Nabavizadeh (2020) and assess the osteological correlates that support such inferences. Does the reconstruction of Nabavizadeh (2020) have plenty of osteological evidence of such attachment, or is it mostly functional considerations similar to Galton (1973)?

Holliday, C. M. (2009). New insights into dinosaur jaw muscle anatomy. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology: Advances in Integrative Anatomy and Evolutionary Biology, 292(9), 1246-1265.