''Catacoeloceras'' is a genus of

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

that lived during Middle

Toarcian The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...

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� ...

. Members of this genus existed from the Bifrons Subzone of the Bifrons Zone to the Variabilis Zone. Their fossils have been found in Europe, northern Africa, Asia, North America and South America. It is believed to have 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 spheroconic shells and these ones were designated as genus '' Transicoeloceras''. Transicoeloceras is now considered a synonym of ''Catacoeloceras'' by some authors, although others still regard it as a valid genus. The ribs on these shells can be either simple or bifurcating. Most species display ventrolateral tubercules and the venter between these tubercles on the body chamber is often smooth and flat. A constriction is present near the mouth border. The genus also exhibits size dimorphism. Genus '' Mucrodactylites'' is considered to be a microconch.

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