Forms of prognathism: Upper Maxilla vs. Lower Maxilla
Top: Prognathism in 16-year-old - Upper jaw together with base of nose is extended forward to an extreme degree, but lower jaw is formed normally.
Bottom: Prognathism in 50-year-old - Superior maxilla normal, but lower jaw protrudes to such an extent that its teeth, when the mouth is closed, lie in front of the upper jaw.
Prognathism is also known as Habsburg (or Hapsburg) Jaw - The term applies to either jaw (“gnath”) being forward of/before the other (“pro”). It’s known as “Hapsburg Jaw” because near the end of their reign, each successive generation of the House of Hapsburg (from the 12th to the final generation) had increasingly severe jaw protrusion going along with other genetic disorders. By the time of Charles II, the jaw deformation (in his case, the protrusion of the lower maxilla, very similar to the lower illustration) was so severe that when combined with mental deficiencies, speech was nearly impossible, and constant drooling was noted even by his flatterers.
Atlas and Text-Book of Dentistry. Gustav Preiswerk, translated by George W. Warren, 1906.