| Progeronia Temporal range: | |
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| Progeronia lictor from Tulear (Madagascar), Kimmeridgian stage | |
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| Genus: | Progeronia (Arkell 1953) |
Progeronia is a genus of ammonites belonging to the family Perisphinctidae. [1]
These fast-moving nektonic carnivores lived in the Jurassic period, from 155.7 to 150.8 Ma. [2]
Species within this genus include: [3]
Shells of Progeronia species can reach a diameter of 6–23 millimetres (0.24–0.91 in). [1] These large shell are large and involute, with a bifurcated or trifurcated ribs. [1]
Fossils of species within this genus have been found in the Jurassic sediments of Algeria and Hungary. [2]
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 appeared during the Devonian, and the last species either vanished in the Cretaceous–Paleogene extinction event, or shortly after during the Danian epoch of the Paleocene.
Belemnoids are an extinct group of marine cephalopod, very similar in many ways to the modern squid and closely related to the modern cuttlefish. Like them, the belemnoids possessed an ink sac, but, unlike the squid, they possessed ten arms of roughly equal length, and no tentacles. The name "belemnoid" comes from the Greek word βέλεμνον, belemnon meaning "a dart or arrow" and the Greek word είδος, eidos meaning "form".
Baculites is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the K-Pg mass extinction event, was named by Lamarck in 1799.
Dactylioceras was a widespread genus of ammonites from the Lower Jurassic period, approximately 180 million years ago (mya).
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
Stephanoceras is an extinct genus of Stephanoceratoid ammonite which lived during the Bajocian. It is the type genus of the family Stephanoceratidae.
Ataxioceras is an extinct Ammonite cephalopod genus confined to the Upper Jurassic of Europe, included in the superfamily Perisphinctoidea.
Audaxlytoceras is an extinct genus of lytoceratid ammonites.
Frechiella is an ammonite with a smooth, somewhat globose involute shell that lived during the later part of the Early Jurassic, which has been found in England and Italy. The shell is coiled so that the outer whorls cover most of the inner, leaving the inner whorls only slightly exposed. The outer rim, known as the venter, is broadly arched, with either a low narrow keel bordered by small grooves, or a large median groove.
Nannolytoceras is an extinct genus of lytoceratid ammonite, family Lytoceratidae, with a stratigraphic range extending from the Bajocian age to Bathonian age.
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.
Harpoceratinae is an extinct subfamily of cephalopods belonging to the family Hildoceratidae. Ammonites of this subfamily had involute and compressed shells with strong keels. Keel might be rarely missing, but this is considered to be an abnormality. This has been observed both in Cleviceras and Harpoceras and called as genus Monestieria, which is now known to be invalid. Another example is Pseudolioceras, whose unkeeled specimen was used as type for description of invalid genus Praehaploceras. Oxyconic forms of this subfamily does not have any keel. Ribs were single, but in some genera also bifurcating with shapes from sigmoidal to falcate. Sometimes, shell can have only striate ribs or is smooth. Tubercules are rare. Dimorphism is known in some genera and it is observable mostly in size. Macrochons can be 4, to 6 times larger than microconchs. As an example, macroconchs of Pseudolioceras are more than 150mm in diameter, while adult microconchs are only 35-50mm. There are big size differences even within dimorphs. Specimens ca be 2, or sometimes even 3 times bigger than other specimens of same dimorph.
Parkinsonia is a genus of ammonites belonging to the family Parkinsoniidae.
Taffertia is an extinct genus of cephalopod belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during Toarcian age in the Falciferum zone and possibly only in Exaratum subzone. Its fossils were found in Canada, Morocco, Algeria and Italy
Osperleioceras is an extinct genus of cephalopod belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during Toarcian stage. Its fossils were found in Europe and South America. First species of this genus, Osperleioceras bicarinatum has evolved in what is now France from Harpoceras subplanatum.
Cleviceras is an extinct genus of cephalopod belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during Toarcian and possibly even uppermost Pliensbachian age. Sometimes, it is considered to be a synonym of Eleganticeras.
Prodactylioceras is genus of ammonite that lived during the Pliensbachian stage of early Jurassic. It has evolved from Reynesocoeloceras, but maybe not directly, but through Bettoniceras. Its fossils were found in Europe, Asia and North America.
This list, 2018 in paleomalacology, is a list of new taxa of ammonites and other fossil cephalopods, as well as fossil gastropods, bivalves and other molluscs that are scheduled to be described during the year 2018, as well as other significant discoveries and events related to molluscan paleontology that are scheduled to occur in the year 2018.
Orthildaites is a genus of ammonites that lived during the lower Toarcian stage of early Jurassic, during Falciferum subzone.
Mercaticeras is an extinct genus of ammonites belonging to the family Hildoceratidae.
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