Middle ear to sounds of higher frequency, because these are better taken up by the inner ear (which also responds to higher frequencies than those of non-mammals). The malleus, or "hammer", evolved from the articular bone of the lower jaw, and the incus, or "anvil", from the quadrate. In other vertebrates, these bones form the primary jaw joint, but the expansion of the dentary bone in mammals led to the evolution of an entirely new jaw joint, freeing up the old joint to become part of the ear. For a period of time, both jaw joints existed together, one medially and one
Anvil tools and pritchels. An anvil may also have a softer "pad" for chisel work. An anvil for a power hammer is usually supported on a massive anvil block, sometimes weighing over 800 tons for a 12-ton hammer; this again rests on a strong foundation of timber and masonry or concrete. An anvil may have a marking indicating its weight, manufacturer, or place of origin. American-made anvils were often marked in pounds. European anvils are sometimes marked in kilograms. English anvils were often marked in hundredweight, the marking consisting of three numbers, indicating hundredweight, quarter hundredweight and pounds. For example, a