Dactylioceras was a widespread genus of ammonites from the Lower Jurassic period, approximately 180 million years ago (mya).
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
Hildoceras is a genus of ammonite from the Jurassic period in the family Hildoceratidae. The shells are characterized by a narrow discoidal evolute shape, keeled venter, concave ribs along the outer flanks, and a shallow spiral groove running along smooth inner flanks. Whorls slightly overlap, cross sections are compressed. The ventral keel is bordered on either side by a shallow groove. The genus was named by Alpheus Hyatt after Saint Hilda in 1876.
Harpoceratinae is an extinct subfamily of cephalopods belonging to the family Hildoceratidae. Ammonites of this subfamily had involute and compressed shells with strong keels. Keel might be rarely missing, but this is considered to be an abnormality. This has been observed both in Cleviceras and Harpoceras and called as genus Monestieria, which is now known to be invalid. Another example is Pseudolioceras, whose unkeeled specimen was used as type for description of invalid genus Praehaploceras. Oxyconic forms of this subfamily does not have any keel. Ribs were single, but in some genera also bifurcating with shapes from sigmoidal to falcate. Sometimes, shell can have only striate ribs or is smooth. Tubercules are rare. Dimorphism is known in some genera and it is observable mostly in size. Macrochons can be 4, to 6 times larger than microconchs. As an example, macroconchs of Pseudolioceras are more than 150mm in diameter, while adult microconchs are only 35-50mm. There are big size differences even within dimorphs. Specimens ca be 2, or sometimes even 3 times bigger than other specimens of same dimorph.
Cleviceras is an extinct genus of cephalopod belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during Toarcian and possibly even uppermost Pliensbachian age. Sometimes, it is considered to be a synonym of Eleganticeras.
Porpoceras is genus of ammonite that lived during the early and middle Toarcian stage of early Jurassic. Members of this genus existed from uppermost part of the Harpoceras serpentinum zone to the Haugia variabilis zone. Their fossils were found in Europe, Asia, North America and South America.
Reynesoceras is genus of ammonites that lived during the upper Pliensbachian stage of early Jurassic. It has evolved from Prodactylioceras, or Cetonoceras. Dactylioceras (Eodactylites) has probably evolved from this genus. Aveyroniceras is a name for macroconchs of this genus. Their fossils were found in Europe, northern Africa, Asia, North America and South America.
Septimaniceras is genus of ammonites that has probably evolved from Peronoceras and lived during the middle Toarcian stage of early Jurassic. Members of this genus existed from Bifrons Subzone to lower part of Variabilis Subzone. Their fossils were found in France, Hungary and probably also in Austria.
Collina is genus of ammonite that lived during lower to upper Toarcian stage of early Jurassic. Members of this genus existed from Braunianus Subzone to Variabilis Zone. Their fossils were found in Europe, Asia, North America and South America. It has evolved from Mesodactylites.
Catacoeloceras is genus of ammonite that lived during middle to late Toarcian stage of early Jurassic. Members of this genus existed from Crassum Subzone of Bifrons Zone to Variabilis Zone. Their fossils were found in Europe, northern Africa, Asia, North America and South America. It has evolved from Peronoceras, or Porpoceras.
Nodicoeloceras is genus of ammonite that lived during early to middle Toarcian stage of early Jurassic. Members of this genus existed from Exaratum Subzone of Falciferum Zone to Commune subzone of Bifrons Zone. Their fossils were found in Europe, northern Africa, Asia, North America and South America. It has probably evolved from Dactylioceras (Orthodactylites) or Kedonoceras and gave rise to Mesodactylites.
The subfamily Nodicoeloceratinae comprises early Jurassic ammonite genera that lived during early to middle Toarcian stage. Origin of this subfamily is unknown, but first genus Nodicoeloceras has evolved from Dactylioceras (Orthodactylites) or Kedonoceras.
Mesodactylites, which is sometimes considered to be a synonym of Nodicoeloceras is genus of ammonite that lived during early to middle Toarcian stage of early Jurassic. Their fossils were found in southern and central Europe and northern Africa. It has evolved from Nodicoeloceras.
Telodactylites, which is sometimes considered to be a synonym of Porpoceras is genus of ammonite that lived during Toarcian stage of early Jurassic. Their fossils were found in Europe, northern Africa and South America. It has probably evolved from Mesodactylites.
Microdactylites, which is sometimes considered to be a synonym of Dactylioceras, is genus of ammonite that lived during early to middle Toarcian stage of early Jurassic. Their fossils were found in England, France, Italy, Germany and Hungary. Species belonging to this genus were microconchs of Dactylioceras.
Mucrodactylites, which is sometimes considered to be a synonym of Collina, is genus of ammonite that lived during middle to late Toarcian stage of early Jurassic. Their fossils were found in Europe, northern Africa and South America. Species belonging to this genus were probably microconchs of Catacoeloceras. As macroconch of M. mucronatus is considered to be Catacoeloceras raquinianum.
Orthildaites is a genus of ammonites that lived during the lower Toarcian stage of early Jurassic, during Falciferum subzone.
Dumortieria is a genus of ammonites belonging to the family Hildocerataceae.
Juraphyllites is a genus of ammonites belonging to the family Juraphyllitidae.
Mercaticeras is an extinct genus of ammonites belonging to the family Hildoceratidae.
