Amaltheus
Encyclopedia
Amaltheus is an oxyconic ammonite
with a fairly open umbilicus, serrated keel, and slightly sigmoidal ribs from the Lower Jurassic
, many of which are strigate. Amaltheus, named by de Montfort ,1808, is indicative of the upper Pliensbachian
stage in Europe, north Africa, Caucasus, Siberia, N. Alaska, Canada, Oregon, and possibly Honduras; and is the type for the Amaltheidae and a member of the Eoderocerataceae.
Two subgenera are recognized. One, A.(Amaltheus) is already described. The other A. (Pseudamaltheus), sometimes expressed as as genus, is a late derivative of {Amaltheus) with an early loss of keel and ribbing and an extreme development of strigation.
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
with a fairly open umbilicus, serrated keel, and slightly sigmoidal ribs from the Lower Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
, many of which are strigate. Amaltheus, named by de Montfort ,1808, is indicative of the upper 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...
stage in Europe, north Africa, Caucasus, Siberia, N. Alaska, Canada, Oregon, and possibly Honduras; and is the type for the Amaltheidae and a member of the Eoderocerataceae.
Two subgenera are recognized. One, A.(Amaltheus) is already described. The other A. (Pseudamaltheus), sometimes expressed as as genus, is a late derivative of {Amaltheus) with an early loss of keel and ribbing and an extreme development of strigation.