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Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids than they are to shelled nautiloids such as the living Nautilus species. The earliest ammonites appear during the Devonian, and the last species vanished in the Cretaceous–Paleogene extinction event.
Acanthohoplites is an extinct genus of ammonites in the family Parahoplitidae that lived in the Aptian and Early Albian stages of the Early Cretaceous.
Australiceras is an extinct ammonite genus from the upper part of the Early Cretaceous, Aptian stage, included in the family Ancyloceratidae.
Anagaudryceras is an extinct genus of ammonite from the later Cretaceous belonging to the Ammonoidea family Gaudryceratidae. Anagaudryceras has a moderately involute shell with a deep umbilicus and strongly ribbed outer whorl. Ribs are thick and rounded and cross over the venter uninterrupted.
Anapachydiscus is an extinct cephalopod genus from the Upper Cretaceous, Santonian - Maastrichtian of Europe, Africa, Madagascar, S.India, N Z, Calif. Mexico, Argentina, and the Antarctic belonging to the ammonoid family Pachydiscidae.
Astiericeras is an ammonite from the Lower Cretaceous, the shell of which is evolute, stout; outer whorl with strong, well spaced, transverse ribs that cross smoothly over the broad venter; early whorls with lateral tubercles. The outer, mature whorl separates from the coil but hooks back quickly, referred to as a heteromorph.
Argonauticeras is an extinct ammonoid cephalopod genus that lived during the latter part of the Early Cretaceous, included in the Lytoceratida and found in lower and possibly middle Aptian marine sediments. It has been thought of as a subgenus of Ammonoceratites.
Balearites is an extinct ancyloceratin genus included in the family Crioceratitidae, subclass Ammonoidea, from the Upper Hauterivian.
Barroisiceras is an acanthoceratacean ammonite from the Upper Cretaceous, Coniacian, included in the family Collignoniceratidae.
Beudanticeras is an extinct cephalopod genus from the Late Cretaceous period; Albian and Cenomanian, belonging to the ammonoid subclass and included in the family Desmoceratidae.
Zurcherella is a Lower Cretaceous (Upper Barremian - Upper Aptian desmoceratid ammonite from France and Colombia. Its shell is moderately compressed and rather involute, with fine sinuous ribs that arise some distance above the umbilical rim. Zurcherella differs from its descendant Uhligella in that in the latter, ribs arise from the umbilical shoulder.
Uhligella is an extinct cephalopod genus from the Early Cretaceous, belonging to the ammonoid subclass and included in the Desmoceratidae.
Ammonitina comprises a diverse suborder of ammonite cephalopods that lived during the Jurassic and Cretaceous periods of the Mesozoic Era. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods.
Turrilites is a genus of helically coiled ammonoid cephalopods from the lower part of the Upper Cretaceous ; generally included in the Ancyloceratina. Previously it was included in the ammonoid suborder, Lytoceratina.
Engonoceratidae is a family of typically compressed, more or less flat sided and involute ammonites from the mid Cretaceous belonging to the Hoplitoidea. shells have flat sided outer rims ( venters), at least in some stage. Single or branching irregular ribs and variably placed tubercles may occur. Sutures have numerous auxiliary and adventive elements of similar form, in general radially arranged. Forwardly divergent saddles tend to be simple, without subdivision. Lobes, pointing apically, may be simple and undivided or may be frilled with short irregular serrations.
Leymeriellidae is a family of Lower Cretaceous ammonites comprising rather small forms distinguished from Hoplitidae by their flattened and grooved ribs and virtual absence of umbilical tubercles. The family is derived from the Desmoceratidae. Leymeriella schrammeni anterior has evolved from Desmoceras keilhacki keilhacki.
Melchiorites is a desmoceratid ammonite genus included in the subfamily Puzosiinae. Member species are characterized by an essentially evolute shell in which the early whorls are smooth, with sinuous radial or oblique constrictions but in which later whorls have feeble intermediate ribs on the outer part of the sides and venter.
Proplacenticeras is a discoidal ammonite from the lower part of the Upper Cretaceous and precursor of the overall similar Placenticeras.
Mammitinae comprises a subfamily within the Acanthoceratidae (Ammonoidea) characterized by moderately to very evolute shells with rectangular to squarish whorl sections along with blunt umbilical and prominent inner and outer ventrolateral tubercles on sparse ribs that may be round and strong, sharp and narrow, or absent. The suture is somewhat simpler than that of the Acanthoceratinae. Range is restricted to the lower Turonian stage of the Upper Cretaceous.
Neocardioceras is a genus of evolute acanthoceratid ammonites from the uppermost Cenomanian, Upper Cretaceous, of Europe, western U.S. and Brazil.
References
- W.J. Arkell, et al., 1957. Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology Part L, Ammonoidea
- Frenguelliceras-Paleodb
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