''Catacoeloceras'' is a 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 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 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 ''
Porpoceras''.
[Kovács, Z. (2014). Toarcian Dactylioceratidae (Ammonitina) from the Gerecse Mts (Hungary). Hantkeniana, 9, 45-77.]
Description
Ammonites belonging to this genus have cadicone shells with depressed, rounded whorl section. Some species have almost sphaeroconic shells and these ones were designated as genus ''
Transicoeloceras'', which is considered to be a synonym of ''Catacoeloceras'' by some authors, while sometimes it is considered to be a valid genus. Ribs can be both simple or bifurcating. In the case of most of the species, ventrolateral tubercules are present. On body chamber, between tubercules, venter can be smooth and flat. Before mouth border, there is constriction. Size dimorphism is present in this genus. Genus ''
Mucrodactylites'' is considered to be a microconch.
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References
Dactylioceratidae
Toarcian life
Early Jurassic ammonites of Europe
Ammonites of Africa
Ammonites of Asia
Ammonites of North America
Ammonites of South America
Ammonitida genera
{{Ammonitina-stub