The 'articular' bone is in the lower jaw of most
tetrapods, including
amphibians,
sauropsids ("reptiles"),
birds and early
synapsids. In these animals it is connected to two other lower jaw bones, the
suprangular and the
angular; and it forms the jaw joint by articulating with the
quadrate bone of the skull.
But in
mammals the articular and quadrate bones have migrated to the
middle ear and are known as the
malleus and
incus. In fact
paleontologists regard this modification as the defining characteristic of mammals.
[1]
References
1. Mammaliformes: Overview - Palaeos