A few thoughts on past comment. There is a reptile alive today that also qualifies as a vertebrate.
The spitting cobra squirts venom from forward facing holes in its fangs.
So there exists a precedent in nature for a reptile squirting a liquid from its mouth. (not flammable, but highly toxic.)
Surly it would be feasible and possible for a large dinosaur or other large beast to have existed that could quirt or spit white phosphorus? White phosphorus is highly toxic, but so is the cobra's venom. White phosphorus will spontaneous combust in air.
In
Job 41:21, I think the reference to fire here could pretty well be satisfied by the use of phosphorus.
Just a few thoughts of mine