Mammal Ear Bones, evolved once, twice or three times?

Mammals have three ear bones (stapes, malleus, and incus) that lay in the air filled cavity called the middle ear. Sound is transported through these bones from the tympanic membrane ("ear drum") to the fluid filled inner ear. A remarkible early Cretacoues fossil mammal (reported in the Feb. 11th issue of Science by Tom Rich et al.) from Victoria, Australia, Teinolophos, exhibits a prominent mandidular trough and well-developed ridge that implys that the middle ear bones were still in contact with the lower jaw. This is not all that surprising since Jurassic mammals such as Morganucodon and Docodon have this primitive feature as well. Yet, based on the "funky" morphology of the teeth, Teinolophos is closely related to living Monotremes. If one excepts a cladogram that places Tricondonts (our Dinosaur eating mammal, see previous post), Multituberculates, Symmetrodonts, Dryolestids, Amphiterium, Marsupials and Placentals into a clade (called Theriimorpha) and Teinolophos and modern Monotremes in a sister clade, the detachment of the ear bones from the lower jaw must have occured twice, once in the ancestor of Monotremes, and once in the ancestor of "Theriimorpha." Although even if you used an alternate cladogram, you only get ear bones detaching from the lower jaw once if you place Teinolophos as the ancestor of all the other mammal groups, but then you would have to neglect all the other characters of Teinolophos, such as those "funky" teeth that place it with Monotremes.