 The Cretaceous Pierre Shale formation of the United States and Canada is well known for the abundant ammonite fauna it yields, including "Baculites", "Placenticeras", "Scaphites", "Hoploscaphites", and "Jeletzkytes", as well as many uncoiled forms.Many of these also have much or all of the original shell, as well as the complete body chamber, still intact.Many Pierre Shale ammonites, and indeed many ammonites throughout earth history, are found inside concretions.