I am not an expert on oviraptorids, cranial anatomy in dinosaurs, jaw function in tetrapods, or any other thing, really. I’m just a dude who likes oviraptorids so much he started trying to learn how to figure out what they ate, and consequently started sharing his ideas for what he thought the skulls seemed to say. This would be based on attempts at thorough reading of the literature, personal observation from that literature, examination (such as it is) of the skulls in question, and of other animals, and the constraints that what animals we have access to alive today may say about the shapes or arrangement of the bones of the jaw and so forth. There’s other stuff, too, like whether or not there’s evidence they were herbivorous, or just omnivorous, or that pesky pet theory about them being ovivorous. The real silly bit among these is that I’ve gained a healthy positive relationship with these dinosaurs, and so avid was my desire to learn of them that I learned a lot more about other stuff, and that’s really the beauty of Science. You almost never end up where you began; if you did, you’re doing it wrong.
So, here are the general placements for the jaw muscles of an oviraptorid, based on my perennial scapegoat Big Beak. There’s a beautiful study cast of this skull in the hands of the Witmer Lab folks, in huge and various perspectives, and there are various casts and photos of it floating around. Unfortunately, study of this specimen is difficult as it is in a perpetual world tour, just like that White Elephant oviraptorid, MPC-D 100/42.
This is not going to be a very helpful post if you want my discussion on the jaw muscle placement, since I am saving that for next year. But know that the sizes for these muscles is arbitrary: I’m not scaling them to size at all, and thus there are no arguments for constraints on how big these are. I will say that despite their slim configuration, these muscles are very large, and very curiously oriented. It has been a fun project to study and look at various animals to examine the various adductor muscle maps, looking at protractors, retractors, orthal adductors, eversive muscles (they try to rotate the jaw around on its long axis, or enable or restrain transverse movements) and depressors. The extent these muscles affect the jaws is interesting, and has been somewhat of a wrench in the works of trying to do this examination purely by paper and pen. Thing is, some of this can be done digitally — should be — but that’s simply not possible for me.