Mammalian Middle Ear Evolution

Not necessarily. A primitive characteristic can survive in some lineages while the derived characteristic develops in others. So Yanoconodon's middle ear may be a morphological intermediate between modern mammals and other mammaliaforms but it doesn't necessarily put Yanoconodon in any sort of direct lineage from ancestral to modern mammals. Yanoconodon may have simply been part of a lineage where the intermediate form of middle ear persisted while the modern mammalian middle ear evolved in a parallel lineage. Therefore the timing of the evolution of the DMME is not given any sort of lower bound by Yanoconodon.The Nature paper describing this discovery by Luo et al. (2007) suggests that this may be a retained feature from the common ancestor of monotremes, eutriconodonts and therians rather than that Yanoconodon is itself some sort of ancestral form and the detachment evolved separately in monotremes and therians. Alternatively the ancestral feature may have re-occurred in Yanoconodon.The only timing we can state at all definitively is an upper bound for when a particular feature appears for the first time in the fossil record, this can only really be a guide to when it actually evolved.As a further instance, many people will present extant modern species as possessing intermediate forms of optical sensory organs along the progression from rudimentary light sensing patches to a vertebrate like compound eye, this doesn't suggest any of these extant modern organisms are in any direct evolutionary lineage leading to modern vertebrates.TTFN,WKEdited by Wounded King, : corrected some typing errors

The first appearance of the DMME in the fossil record, it can have evolved no later than that, although obviously if we are talking about 2 separate lineages where the trait evolves independently then its a bit more complex.The earliest know mammalian fossil with a DMME is, I think, Hadrocodium (Luo et al., 2007). Hadrocodium is dated at ~195 MYA, but even before then the earliest instance of the DMME was at ~150 MYA, still well before your Yanoconodon date of 125 MYA. This is not supported from the original paper or from the Wikipedia article. In fact looking at the wikipedia article you lined to I have to ask if you even bothered to actually read it? It says right there in the wiki ... So do you understand what a transitional fossil is yet? As I pointed out right at the start all it means is that it shows an intermediate morphology in terms of the middle ear between modern mammals and their early mammaliaform ancestors, not that it is itself necessarily an ancestral species to modern mammals.Therefore we can have an 'intermediate fossil' appear in the fossil record well after the first instance of the trait it is an intermediate stage to.To reiterate ... it was a transitional but for all we know it was extant after the DMME was already established in the mammalian lineage. From considerably before that although related mammaliaforms, such as Yanoconodon, obviously still showed the transitional middle ear morphology at later times. No and no. What the evolutionary theory did predict was that such an intermediate form would exist. When it is actually found in the fossil record is relatively immaterial.TTFN,WK

It includes changes to the ear but not those changes which would produce what is termed the definite mammalian middle ear (DMME) in which the connection to the mandible is entirely lost when Meckel's cartilage is absorbed. It is this specific change that AOK seems to be focusing on and for which Yanoconodont is presented as an intermediate form.TTFN,WK

Not really. H. wui is the same as Hadrocodium which I mentioned in Message 11, The paper describing H. wui (Luo et al., 2001) definitely does mention Meckel's cartilage ... So there is strong evidence for a detached middle ear already in H. wui. So a common ancestor showing an intermediate middle ear, if that is what we are looking for, should have been extant before ~195 MYA.I'm not sure what the point of this line of thought is though since Yanoconodon shows us exactly what we would expect that intermediate middle ear morphology to look like with all the ossicles developed but the malleus is still attached to Meckel's cartilage when the cartilage ossifies.Given the fact that Hadrocodium was already mentioned in his references one has to wonder if AOK was trying to pull a fast one; getting people to state that ToE would predict a date after Yanoconodon appears in the fossil record for the first appearance of the DMME so he can then whip out Hadrocodium and say 'ah hah! This feature appears in the fossil record almost 100 MY before Yanoconodon, therefore evolution is false!'. Pretty much all of the early mammaliaforms.TTFN,WK

Hi AOK,Do you think you have a satisfactory answer to your OP now?TTFN,WK