Cornified papillae (both labial and buccal) are found in much of the mouth of at least cattle and elands (to my knowledge so far). They are definitely not found to any similar degree in horses. I seem to recall a few raised bumps in the corner of the mouth of our (now deceased) family dog, but I just did a quick check on my brother's pit bull here, and [updated 12/29, now that I inspected her lips under good light] she has a few widely spaced papillae that seem to be uncornified (or at least not noticeably cornified). Broader sampling needed . . .
Just in front of the incisors the labial papillae are low rounded bumps (seen on both upper and lower lips in this pic. She has a bit of an underbite since a good portion of the skull's weight is resting on the back of the jaw, pushing the jaw forward. And there are no upper incisors on any bovid, in case you are wondering.)
What surprised me was how the papillae became long and pointed, shaped like sharks' teeth in the angle of the mouth - individually and in their spiral out-folding arrangement collectively.
The papillae look to be part of a widespread pattern of epithelial modification in the mouth; you can see lines of somewhat similar bumps on the roof of the mouth (hard palate). (Sorry for the washed out pic; I had one hand dedicated to the specimen, one had dedicated to the camera, no help, my contacts were corroding my eyeballs, and it was midnight).
According to Budras & Habel's Bovine Anatomy (1st ed.) both labial and buccal papillae help keep cud in the mouth during the wide lateral jaw movements during rumination (thank you, GoogleBook Search). Which might help to explain why dogs and horses (and people) don't have these papillae.
And now you (and I) know!