Kimmeridgian
[2] The Kimmeridgian Stage takes its name from the village of Kimmeridge on the Dorset coast, England.The name was introduced into the literature by French geologist Alcide d'Orbigny in 1842,[3] although it seems to have been first suggested by Thomas Webster in 1812.The differences have not yet been fully resolved; As of 2004[update] Tithonian is the uppermost stage of the Jurassic in the timescale of the ICS.[5] The base of the Kimmeridgian is at the first appearance of ammonite species Pictonia baylei in the stratigraphic column.[8] The top of the Kimmeridgian (the base of the Tithonian) is at the first appearance of ammonite species Hybonoticeras hybonotum.