Amaltheidae
Encyclopedia
Amaltheidae is a family of eoderoceratacean
ammonitids from the Lower Jurassic consisting of genera characterised by stigated discoidal oxycones—narrow involute shells with narrowly rounded to angular venters that bear a series of grooves, or ridges, along broad flanks, which according to the Treatise
L, 1957, evolved into strongly ribbed planulates (discoidal evolute shells) with quadrate whorls, typically with crenulated keels; involving all together four genera.
Donovan in Donovan et al. (1981) retains the Amaltheidae in the sense of Arkell, et al., in the Treatise in Invertebrate Paleontology, Part L
but synonomizes Pseudoamaltheus with Amaltheus
, (a subgenus in the Treatise), reducing the number of valid genera to three. These are Amaltheus
, Amauroceras
, and Pleuroceras.
Amaltheus, included subgenera, is oxyconic, keeled, strigated, and ribbed on the outer flanks.
Amauroceras is smooth, compressed, without ribs or stigation, and the keel is reduced.
Pleuroceras has a planulate shell with a quadrate whorl section, bearing strong radial ribs ending in ventro-lateral tubercles. The venter is tabulate with a strong serrated keel.
The Amaltheidae are derived from the Liparoceratidae
and have a principally boreal
distribution
Eoderocerataceae
Eoderocerataceae is a superfamily of true ammonites from the Lower Jurassic, comprising seven phylogenetically related families, characterized in general by having ribbed evolute shells that commonly bear spines or tubercles...
ammonitids from the Lower Jurassic consisting of genera characterised by stigated discoidal oxycones—narrow involute shells with narrowly rounded to angular venters that bear a series of grooves, or ridges, along broad flanks, which according to the Treatise
Treatise on Invertebrate Paleontology
The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
L, 1957, evolved into strongly ribbed planulates (discoidal evolute shells) with quadrate whorls, typically with crenulated keels; involving all together four genera.
Donovan in Donovan et al. (1981) retains the Amaltheidae in the sense of Arkell, et al., in the Treatise in Invertebrate Paleontology, Part L
Treatise on Invertebrate Paleontology
The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
but synonomizes Pseudoamaltheus with Amaltheus
Amaltheus
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...
, (a subgenus in the Treatise), reducing the number of valid genera to three. These are Amaltheus
Amaltheus
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...
, Amauroceras
Amauroceras
Amauroceras is an extinct genus of eoderoceratacean ammonites in the family Amaltheidae.-References:* Arkell, et al, 1957. Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology, Part L; Geological Society of America and University Kansas press....
, and Pleuroceras.
Amaltheus, included subgenera, is oxyconic, keeled, strigated, and ribbed on the outer flanks.
Amauroceras is smooth, compressed, without ribs or stigation, and the keel is reduced.
Pleuroceras has a planulate shell with a quadrate whorl section, bearing strong radial ribs ending in ventro-lateral tubercles. The venter is tabulate with a strong serrated keel.
The Amaltheidae are derived from the Liparoceratidae
Liparoceratidae
Liparoceratidae is a family of eoderoceratacean ammonites from the Lower Jurassic that combines genera with a variety of forms including dimorphs that change from one form to another during ontogeny....
and have a principally boreal
Boreal
Boreal may refer to*Boreal ecosystem**Boreal climate, the climate found in a region of boreal forests, and designated Dfc, Dwc or Dsc in the Köppen climate classification scheme.*boreal forest*Boreal forest of Canada*Boreal Bluet...
distribution