The Paleobiology Database

Palfy North American Ammonite Chrons

Interval	Maximum correlate	Minimum correlate	Ma

Epizigzagiceras	Late/Upper Bajocian
			168.4

Rotundum	Late/Upper Bajocian


Oblatum	Early/Lower Bajocian


Kirschneri	Early/Lower Bajocian


Crassicostatus	Early/Lower Bajocian


Widebayense	Early/Lower Bajocian
			170.7

Howelli	Aalenian
			177.6

Scissum	Aalenian


Westermanni	Aalenian


Yakounensis	Late/Upper Toarcian


Hillebrandti	Late/Upper Toarcian


Crassicosta	Middle Toarcian
			180.1

Planulata	Middle Toarcian
			182

Kanense	Early/Lower Toarcian
			183.7

Carlottense	Late/Upper Pliensbachian
			184.1

Kunae	Early/Lower Pliensbachian	Late/Upper Pliensbachian
			185.7

Freboldi	Early/Lower Pliensbachian
			186.7

Whiteavesi	Early/Lower Pliensbachian


Imlayi	Early/Lower Pliensbachian


Tetraspidoceras	Late/Upper Sinemurian	Early/Lower Pliensbachian
			190.7

Plesechioceras harbledownense	Late/Upper Sinemurian


Asteroceras varians	Late/Upper Sinemurian


Arnioceras arnouldi	Early/Lower Sinemurian


Coroniceras	Early/Lower Sinemurian


Canadensis	Hettangian	Early/Lower Sinemurian
			195.3

Pseudaetomoceras	Hettangian
			196.6

Franziceras	Hettangian


Euphyllites	Hettangian


Psiloceras	Hettangian
			199.6

Authorizer: J. Alroy Enterer: J. Alroy

Continent: North America Rank of each interval: chron/zone

Basis of scale: paleontological