Arietitidae
Encyclopedia
Arietitidae is a family of true ammonites that make up part of the superfamily Psilocerataceae
. They comprise medium-size to large or gigantic genera which in general are strongly ribbed, tuberculate in some, with keeled or grooved and keeled venters, and well differentiated ammonitic sutures. The aptycus is single valved with a shiny, concentrically striated surface.
Arietitidae dominated Lower Jurassic, Sinemurin ammonites, world wide, extending into the lower Pliensbachian
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The Arietitidae may have their origin in the Schlotheimiidae if not directly from the Psiloceratidae, and is the probably source for the Oxynoticeratidae
Psilocerataceae
The Psilocerataceae is a superfamily of Early Jurassic ammonoid cephalopods proposed by Alpheus Hyatt in 1867, assigned to the order Ammonitida....
. They comprise medium-size to large or gigantic genera which in general are strongly ribbed, tuberculate in some, with keeled or grooved and keeled venters, and well differentiated ammonitic sutures. The aptycus is single valved with a shiny, concentrically striated surface.
Arietitidae dominated Lower Jurassic, Sinemurin ammonites, world wide, extending into the lower Pliensbachian
Pliensbachian
The Pliensbachian is an age of the geologic timescale or stage in the stratigraphic column. It is part of the Early or Lower Jurassic epoch or series and spans the time between 189.6 ± 1.5 Ma and 183 ± 1.5 Ma . The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.The...
.
The Arietitidae may have their origin in the Schlotheimiidae if not directly from the Psiloceratidae, and is the probably source for the Oxynoticeratidae
Oxynoticeratidae
Oxynoticeratidae is a family of true ammonites from the Lower Jurassic. They are part of the superfamily Psilocerataceae, characterized by mostly involute, oxyconic shells with narrow venter and compressed, lanceolate whorl section. Suture is ammonitic. Ribbing is feeble, hardly functional and...