The Aalenian is a subdivision of the Middle Jurassic Epoch/Series of the geologic timescale that extends from about 174.7 ±0.8 Ma to about 170.9 ±0.8 Ma. It was preceded by the Toarcian and succeeded by the Bajocian.
In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma. The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age.
Stephanoceras is an extinct genus of Stephanoceratoid ammonite which lived during the Bajocian. It is the type genus of the family Stephanoceratidae.
Abbasites is an extinct genus of ammonites from the early Middle Jurassic epoch, included in the ammonitid family Erycitidae.
Arcticoceras is an extinct ammonoid cephalopod genus from the late Middle Jurassic belonging to the ammonite family Cardioceratidae, more commonly found to high northern latitudes.
Arctocephalites is an extinct ammonitic cephalopod genus from the Middle Jurassic with a wide northern distribution belonging to the stephanoceratacean family, Cardioceratidae.
Glochiceras is a haploceratid ammonite characterized by a small, smooth, compressed, evolute shells with large lappets and a median lateral groove. Its geographic distribution is fairly cosmopolitan, but it is limited stratigraphically to the Oxfordian and Kimmeridgian stages in the Upper Jurassic.
Cadomites is an extinct ammonite genus from the superfamily Stephanoceratoidea that lived during the Middle Jurassic.
Emileia is an extinct genus from a well-known class of fossil cephalopods, the ammonites, that lived during the early part of the Bajocian.
Durotrigensia is a genus of ammonites (Ammonitida) in the perisphinctoid family Parkinsoniidae.
Phaulostephanus is an extinct genus from the ammonoid family Stephanoceratidae, which is part of the ammonitid superfamily Stephanoceratoidea, that lived during the early Middle Jurassic.
Parastrenoceras is an extinct genus from the ammonoid cephalopod order Ammonitida, included in the family Spiroceratidae that lived during the Bajocian stage of the Middle Jurassic.
Nannolytoceras is an extinct genus of lytoceratid ammonite, family Lytoceratidae, with a stratigraphic range extending from the Bajocian age to Bathonian age.
Hyperlioceras is an extinct genus of cephalopod included in the ammonitid family Graphoceratidae that lived during the Bajocian stage of the Middle Jurassic. The type species is Hyperlioceras discites
Graphoceras is an extinct ammonite genus included in the hildoceratacean family Graphoceratidae that lived during the Aalenian and Bajocian stages, Middle Jurassic in what is now Europe, north Africa, and Iran.
Parkinsoniidae is a family of ammonites belonging to the order Ammonitida. The cephalopod family lived from the Bajocian stage to the Bathonian age of the Middle Jurassic.
Parkinsonia is a genus of ammonites belonging to the family Parkinsoniidae.
Skirroceras is a Stephanoceratacean (ammonite) genus belonging to the family Stephanoceratidae. These fast-swimming carnivores lived during the Jurassic period, in the Bajocian age.
Cadoceras is an extinct ammonite genus belonging to the Cardioceratidae that lived during the Jurassic period from the late Bajocian to the early Callovian.
Skirroceras macrum is a Stephanoceratacean (ammonite) species belonging to the family Stephanoceratidae.
