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| Fossil of Mercaticeras species, from Luserna, Trento | |
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| Genus: | †Mercaticeras |
Mercaticeras is an extinct genus of ammonites belonging to the family Hildoceratidae.
The genus name Mercaticeras derives from Michele Mercati (a Tuscan physician who lived in the 16th century, superintendent of the Vatican Botanical Gardens) and ceras = horn, therefore the genus name means horn of Mercati. [1]
Mercaticeras shows a subquadratic section, sometimes wider than high. The shell is averagely evolute, with a spiral that grows more rapidly in the internal whirls. It is adorned by sturdy, clavate, simple ribs. The suture is simple. [1]
These ammonites lived in the Jurassic, Middle Toarcian age, Bifrons Zone to lower Variabilis/Gradatus Zone (age range: 182.0 to 175.6 million years ago). [2]
Fossils of this genus can be found in Albania, Algeria, Austria, Bulgaria, Canada, France, Germany, Greece, Herzegovina, Hungary, Italy, Morocco, Portugal, Spain, Switzerland, Tunisia, Turkey. [3] [4]
Species within this genus include: [3]
The suprageneric classification has been discussed in the literature. Researchers of the Toarcian Mediterranean domain agree that Mercaticeras belongs to the subfamily Mercaticeratinae Guex, 1974 (Hildoceratidae) with genera Praemercaticeras Venturi, 1981, Pseudomercaticeras Merla, 1932, Merlaites Gabilly, 1974, Crassiceras Merla, 1932, and Pseudocrassiceras Rulleau et Jattiot, 2019. [5]
Dactylioceras was a widespread genus of ammonites from the Lower Jurassic period, approximately 180 million years ago (mya).
Abbasites is an extinct genus of ammonites from the early Middle Jurassic epoch, included in the ammonitid family Erycitidae.
Arctomercaticeras is an extinct genus of cephalopod belonging to the Ammonite subclass and the family Hildoceratidae that lived during the Early Jurassic in the Arctic zone of Russia.
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.
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 Hyatt after Saint Hilda in 1876.
Hildoceratoidea, formerly Hildoceratacaea, is a superfamily of compressed or planulate ammonites, some tending to develop acute outer rims; generally with arcuate or sigmoidal ribs. Aptichus were found in place are double-valved.
Harpoceras is an extinct genus of ammonite belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during the Toarcian age from the Falciferum zone to the Commune subzone of the Bifrons zone. They were fast-moving nektonic carnivores.
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.
Hammatoceras is a genus of ammonites belonging to the family Hammatoceratidae which lived during the Toarcian stage of the Early/Lower Jurassic between about 184 and 175 million year ago.
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
Porpoceras is genus of ammonite that lived during the early and middle Toarcian stage of early Jurassic. Members of this genus existed from uppermost part of the Harpoceras serpentinum zone to the Haugia variabilis zone. Their fossils were found in Europe, Asia, North America and South America.
Reynesoceras is genus of ammonites that lived during the upper Pliensbachian stage of early Jurassic. It has evolved from Prodactylioceras, or Cetonoceras. Dactylioceras (Eodactylites) has probably evolved from this genus. Aveyroniceras is a name for macroconchs of this genus. Their fossils were found in Europe, northern Africa, Asia, North America and South America.
Catacoeloceras is a genus of ammonite that lived during middle to late Toarcian stage of early Jurassic. Members of this genus existed from Bifrons Subzone of Bifrons Zone to Variabilis Zone. Their fossils were found in Europe, northern Africa, Asia, North America and South America. It has evolved from Peronoceras, or Porpoceras.
Nodicoeloceras is genus of ammonite that lived during early to middle Toarcian stage of early Jurassic. Members of this genus existed from Exaratum Subzone of Falciferum Zone to Commune subzone of Bifrons Zone. Their fossils were found in Europe, northern Africa, Asia, North America and South America. It has probably evolved from Dactylioceras (Orthodactylites) or Kedonoceras and gave rise to Mesodactylites.
Transicoeloceras, which is sometimes considered to be a synonym of Catacoeloceras is genus of ammonite that lived during Toarcian stage of early Jurassic. Their fossils were found in Hungary, Italy, France, southern Spain and South America. It has evolved from Mesodactylites.
The subfamily Dactylioceratinae comprises early Jurassic ammonite genera that lived during Upper Pliensbachian to Upper Toarcian stage. These dactylioceratids existed from Margaritatus ammonite Zone, when they have evolved from Reynesocoeloceratinae and died out in Variabilis Zone without leaving any descendants.
Microdactylites, which is sometimes considered to be a synonym of Dactylioceras, is genus of ammonite that lived during early to middle Toarcian stage of early Jurassic. Their fossils were found in England, France, Italy, Germany and Hungary. Species belonging to this genus were microconchs of Dactylioceras.
Mucrodactylites, which is sometimes considered to be a synonym of Collina, is genus of ammonite that lived during middle to late Toarcian stage of early Jurassic. Their fossils were found in Europe, northern Africa and South America. Species belonging to this genus were probably microconchs of Catacoeloceras. As macroconch of M. mucronatus is considered to be Catacoeloceras raquinianum.
Hildoceratinae is an extinct subfamily of cephalopods belonging to the family Hildoceratidae. Ammonites of this subfamily had shells with elliptical or quadrate whorl section with keel or tricarinate, bisulcate venter. Ribs were variable, from falcate to strongly angled and from fine to strong. They can be interrupted by spiral groove in midlateral part of the shell. While some species can be smooth, strongly ribbed ones can have tubercules. Microconchs have short lapplets that is in its shape similar to the shape of growth lines in spiral midlateral groove.
Federico Venturi was an Italian paleontologist. He is internationally known as a specialist of Early Jurassic ammonites.
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