''Porpoceras'' is genus of

ammonite 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 (i.e., octopuses, squid and cuttlefish) ...

that lived during the early and middle

Toarcian 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 (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarcian ...

stage of

early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

. Members of this genus existed from uppermost part of the ''

Harpoceras ''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.Sepkoski, JacSep ...

serpentinum'' zone to the '' Haugia variabilis'' zone.Jattiot, R., Fara, E., Brayard, A., & Vennin, E. (2016). Revised stratigraphic range of the Toarcian ammonite genus Porpoceras Buckman, 1911. Geodiversitas, 38(4), 505-513. Their fossils were found in Europe, Asia, North America and South America.

Description

Ammonites belonging to this genus have evolute shells, with compressed to depressed whorl section. Flanks were slightly convex and venter has been low. Whorl section is subrectangular. Prorsiradiate ribs are strong and fibulate on inner whorls and tuberculate to spined on the place of ventrolateral shoulder.KOVÁCS, Z. (2014). Toarcian Dactylioceratidae (Ammonitina) from the Gerecse Mts (Hungary). Hantkeniana, 9, 45-77. It differs from '' Peronoceras'' by not having compressed whorl section and regular fibulation. ''

Catacoeloceras ''Catacoeloceras'' is a genus of ammonite that lived during Middle Toarcian stage of early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earl ...

'' is also similar, but it has regular ventrolateral tubercules and is missing fibulation.

References

Dactylioceratidae Toarcian life Early Jurassic ammonites of Europe Early Jurassic ammonites of Africa Early Jurassic ammonites of Asia Early Jurassic ammonites of North America Early Jurassic ammonites of South America Ammonitida genera {{Ammonitina-stub