Opportunely enough, details of a new intermediate form, Liaoconodon hui, have just been published.Look, you believe life evolves so something like this is evidence to your mind, although it is only evidence because it fits with your theory, not the kind of evidence that actually proves anything. It's just another of those plausibilities that the whole theory is built of, just an exercise in recognizing structural analogues.
Some details here:The new genus and species described by Meng et al. comes form the exquisitely preserved Jehol biota of Liaoning, and shows the last tenuous connection between the mammalian ear ossicles and the lower jaw, via Meckel’s cartilage, an ancient part of the lower jaw lying along the medial surface of the dentary. They refer to it as a “transitional mammalian middle ear”, the transition being between the mandibular middle ear (i.e. attached to the lower jaw) of the earliest mammals (and most advanced reptiles), and the definitive mammalian middle ear present in the adults of all extant mammals, in which there is no persistent connection between the middle ear and the lower jaw.Now in modern mammals Meckel's cartilage disappears during embryological development:Living mammals, including humans, have Meckel's cartilage as embryos, but it disappears as they mature. In the L. hui fossil - an adult - it is ossified and the fossil shows how it supported some of the post-dentary bones as they shifted into the ear.This is more evidence for the evolution of this irreducibly complex structure.
Meanwhile, creationists continue to attribute this sort of structure to entirely unknown and unevidenced processes; and this they do based only on not being able to see how this sort of thing evolved --- despite the fact that, dammit, we can.
Since I do not believe life evolves, except for variations within a species, such phenomena are simply examples of design similarities that occur everywhere in nature. Its function in the embryo may be quite different than Evo theory makes of it, you're simply smugly content with a facile explanation that fits with the theory, and of course there is no way to falsify such an explanation so you have no fear that anything a creationist might say could unsettle your certainty.
And, we CAN "see how this sort of thing evolved" BASED ON YOUR ASSUMPTION THAT IT DID. We can "see" the same thing you see, we simply recognize that it's nothing but another imaginative construction and not evidence in the true sense at all.
Also, you ask us to take a lot for granted even in the description of the evidence. You ask us to believe that this really is the same cartilage in all the examples you mention though you provide no photographs to demonstrate it, that it occurs in the embryos of mammals and humans -- does it look exactly the same? Are you sure it's the same structure? -- and that it later "disappears," and that its function is as you describe with relation to dental development. Hey, maybe it is, but as I recall, a famous propagator of the "Biogenetic Law," Ontogeny Recapitulates Phylogeny, which my generation was raised on, had so fudged the illustrations he offered in proof of his thesis that eventually they were recognized as fraud -- all in the service of proving his belief in that principle and in evolution itself.
Yet we're still only presented with raw descriptions such as the above and not shown anything that would allow us to judge for ourselves whether the researchers are interpreting the phenomena correctly or perhaps imposing their own bias on the data -- fudging a bit here and there.
In any case, the occurrence of any particular structure across many species doesn't prove evolution, merely design similarity.
Oh, and terms like "ancient" and "modern" -- as well as "intermediate" -- are also interpretive bias imposed on the data. A species of word magic.
Evolutionary "science" is really laughable when you take the time to ask the right questions.