April 13, 2011
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| Close-up view of Liaoconodon hui: the ear ossicles (circular ectotympanic area) and the ossified Meckel's cartilage aligned with the lower jaw. Image courtesy of Jin Meng. |
Described by paleontologists from the American Museum of Natural History and the Chinese Academy of Sciences, Liaoconodon hui is a complete fossil mammal from the Mesozoic that includes the long-sought transitional middle ear between reptiles and true mammals. The specimen shows the bones associated with hearing in mammals— the malleus and incus, as well as the ectotympanic area —are decoupled from the lower jaw, as had been predicted, but were held in place by an ossified cartilage that rested in a groove on the lower jaw.
“People have been looking for this specimen for over 150 years since noticing a puzzling groove on the lower jaw of some early mammals, “ says Jin Meng, curator in the Division of Paleontology at the Museum and first author of the paper. “Now we have cartilage with ear bones attached, the first clear paleontological evidence showing relationships between the lower jaw and middle ear.”
The new research also suggests that the middle ear evolved at least twice in mammals, for monotremes and for the marsupial-placental group.
Jin Meng talks about the discovery in the video below.
