‘A fossil unearthed in northeastern China has middle ear anatomy somewhere between more primitive and modern mammals, confirming for the first time transitional steps in the evolution of the important structure.
Scientists suspected the malleus or hammer, incus or anvil, and stapes or stirrup, split off from a location at the hinge of the lower jaw to become separate structures.
The new find, 125 million-year-old Yanoconodon allini, has middle ear bones that are partly separated from the jaw, but remain connected by a bridge of ossified cartilage. [..]
As Dr. Luo put it: “We have now a clear case documenting why a very elaborate and very delicate and very sophisticated ear structure came about and how it came about.”‘