Jurassic ammonites

Asteroceras (from Ancient Greek ἀστήρ (astḗr), meaning "star", and κέρας (kéras), meaning "horn") is an extinct genus of cephalopod belonging to the Ammonite subclass. These fast-moving nektonic carnivores lived during the Triassic and Jurassic periods (from 205.6 to 189.6 Ma).

Dactylioceras was a widespread genus of ammonites from the Lower Jurassic period, approximately 180 million years ago (mya).Like many other ammonites, the genus Dactylioceras is extremely important in biostratigraphy, being a key index fossil for identifying their region of the Jurassic. It had a nearly cosmopolitan distribution during the time it existed.

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 Eoderoceratoidea.

thumb|Recreation of Hildoceras thumb|Hildoceras species from the Toarcian Bifrons Zone of the Gerecse Mts, Hungary. Collection Eötvös University, Dep. Palaeontology, Budapest. 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 Hy

Phylloceras is an extinct genus of ammonoid cephalopods belonging to the family Phylloceratidae. These nektonic carnivores lived from Early Jurassic (Hettangian age) to Late Cretaceous (Maastrichtian age) (from 201.30 to 66.043 Ma).

Psiloceras is an extinct genus of ammonite. Psiloceras is among the earliest known Jurassic ammonites, and the appearance of the earliest Psiloceras species form the definition for the base of the Jurassic. Unlike most earlier ammonites, which had complex shell shapes and ornamentation, Psiloceras had a smooth shell.

thumb|right|Arietites bucklandi fossil at the Geological Museum in Copenhagen

Stephanoceras (meaning crown horn) is an extinct genus of Stephanoceratoid ammonite which lived during the Bajocian (Middle Jurassic). It is the type genus of the family Stephanoceratidae.

Kosmoceratidae is an extinct ammonite family from the Callovian (Middle Jurassic) to Early Cretaceous.

Arnioceras is an extinct genus of large, evolute, discoidal ammonite from the Lower Jurassic. The shell is normally coiled so that all whorls are exposed. Sides bear strong sharp ribs that are straight until reaching the ventrolateral edge where they swing forward and fade. The rim (venter) is keeled and free of grooves.

Lytoceras is an ammonite genus that was extant during most of the Jurassic and Cretaceous periods, and is the type genus for the family Lytoceratidae. These cephalopods were fast-moving nektonic carnivores.

Peltoceras is an extinct ammonite genus from the aspidoceratid subfamily Peltoceratinae that lived during the later part of the Middle Jurassic (U Callovian).

Aspidoceras is an extinct ammonoid cephalopod genus belonging to the family Aspidoceratidae.

Berriasella is a discoidal evolute perisphinctacean ammonite, and type genus for the neocomitid subfamily Berriasellinae. Its ribbing is distinct, consisting of both simple and bifurcated ribs that extend from the umbilical seam across the venter; its whorl section generally compressed, the venter more or less narrowly rounded. The species Berriasella jacobi traditionally has been regarded an index fossil defining the base of the Cretaceous, however since 2016 this had been replaced by the first occurrence of Calpionella alpina. Some authors regard B. jacobi as instead belonging to the genus S

Bifericeras is a Lower Jurassic ammonite belonging to the family Eoderoceratidae, and sometimes placed in the subfamily Xipherceratinae. Whorls are strongly depressed, but still evolute in coiling. The early growth state is prolonged, and smooth, followed by a late growth stage with rounded, straight, bituberculate ribs.

Oppelia is a haploceratoid ammonite and type genus for the Oppeliidae that lived during the Middle Jurassic. Shells of Oppelia are involute with a small to moderate size umbilicus, bluntly rounded to sharp venter, and deeply impressed dorsum. Sides are generally smooth but may be variously ribbed on the outer flanks. Similar and related genera include Oxycerites and Oecotraustes.

Asthenoceras is a genus of ammonoid from the Middle Jurassic (Lower Bajocian) with dwarfish, evolute, smooth, compressed, discoidal, strongly keeled shell. Asthenoceras belongs to the Sonniniidae and may be a subgenus of the Lower Jurassic (Upper Toarcian) Grammoceras.

Promicroceras is an extinct ammonite genus from the upper Sinemurian (Lower Jurassic) of Europe, named by Leonard Spath in 1925. Promicroceras is included in the family Eoderoceratidae, which is part of the ammonitid superfamily Eoderoceratoidea.

Hildoceratidae is a family of ammonoid cephalopods from the Lower Jurassic, lower Pliensbachian (Jamesoni zone) to lower Bajocian (maybe even upper Bajocian) substages, generally with strongly ribbed, involute shells. They are combined with the Hammatoceratidae (= Phymatoceratidae), Graphoceratidae, and Sonniniidae to make up the Hildoceratoidea.

Idoceras is a genus of perisphictacean ammonite, belonging to the Perisphinctidae subfamily Idoceratinae. The genus is known from the Upper Jurassic, with a widespread distribution. Shells of Idoceras are evolute, with a wide umbilicus; ribbing strong, bifurcate high on flanks. Suture simpler than in the similar Ataxioceras.

Parkinsoniidae is a family of ammonites belonging to the order Ammonitida. The cephalopod family lived from the Bajocian stage to the Bathonian age of the Middle Jurassic.

genus of molluscs (fossil)

Leptosphinctes is an extinct genus from a well-known class of fossil cephalopods, the ammonites. It lived during the Jurassic Period, which lasted from approximately 200 to 145 million years ago.

Otoites is the type genus of the ammonite family Otoitidae that live during the Middle Jurassic.

Quenstedtoceras is a genus of ammonoid cephalopods that lived during the latter part of the Jurassic period in what is now France, Poland, Germany, and the United Kingdom.

Cardioceras is an extinct ammonite genus belonging to the family Cardioceratidae. These fast-moving nektonic carnivores lived during the Jurassic period, Oxfordian age.