Both left and right quadratojugals are fused to the quadrates.
A groove is present laterally on the quadrates where the dorsal processes of the quadratojugals overlap.
The dorsal end of the right quadrate is expanded slightly and narrow anteroposteriorly.
Part of the pterygoid overlaps and is fused to the anteromedial end of the pterygoid process of the left quadrate.
Originally, the quadrate-mandibular joint was probably placed under the mid-region of the orbit.
The bone is triradiate in lateral view, with a ventral process that is concave on its medial side for articulation with the head of the quadrate.
The quadrate is subtriangular, fan-shaped.
In later mammal ancestors, the articular and quadrate separated from the jaw joint while the articular developed into the malleus bone of the middle ear.
