Cynodonts had a more mammal-like jaw musculature, but the ear ossicles were still attached to the lower jaw, as they are in reptiles.
Dissection of the middle ear has revealed morphological defects of the ossicles which disrupt the ossicular chain resulting in a conductive hearing loss.
Much scarcer are other types of bituminous skeletal limestones, which consist mostly of crinoid ossicles associated with rare brachiopod and trilobite remains.
Mandible, maxilla and auditory ossicles (malleus, incus and stapes) are branchial arch derivatives.
Belemnites, bivalves, crinoid ossicles and wood remains are scattered throughout.
The ossicles function as an impedance transformer to provide sufficient force at the oval window to move the fluid which fills the cochlea in response to external acoustic vibrations.
As well as the local fauna, the mudstone also contains smaller debris: five-sided star-shaped crinoid ossicles, a few small belemnites, a possible echinoid spine impression and probable fish scales.
All of the ossicles move as a unit.
