[massifist]

Is there a reason why they don't suggest the possibility that this was a mammal scavenging the carcass of a dinosaur?

And would this be a surprise, other than providing an interesting specimen?

[riccardomc]

Yes, there is a reason: “The lack of bite marks on the dinosaur skeleton, the position of the mammal atop the dinosaur, and the grasping and biting actions of the mammal, collectively signal that the mammal was preying on the weakened dinosaur when the two were suddenly entombed by a volcanic debris flow,”