''Ataxioceras'' is an extinct

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) ...

cephalopod genus confined to the Upper Jurassic of Europe, included in the superfamily

Perisphinctoidea Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic (Bajocian) to Lower Cretaceous (Barremian) ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the ven ...

. Previously ''Ataxioceras'' was assigned to the Perisphinctidae but has now been placed in the

Ataxioceratidae Ataxioceratidae is an extinct Ammonite cephalopod family included in the superfamily Perisphinctoidea. These fast-moving nektonic carnivores lived during the Jurassic and Cretaceous periods. Genera *'' Catutosphinctes'' *'' Choicensisphinctes'' ...

for which it is the type genus. These fast-moving nektonic carnivores lived during the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

period, from 155.7 to 150.8 Ma.

Description

The shell is evolute, strongly ribbed and moderately umbilicate. Primary ribs, on the order of 32 -36 per whorl, are sharp and widely spaced, originate at the umbilical shoulder. Secondary ribs form about mid flank, generally by trifurcation, but sometimes quadrifurcation (splitting into threes or sometimes fours) of the primaries. The umbilicus is about 0.4 the shell diameter.

Distribution

Fossils of species within this genus have been found in the

sediments in Germany, France, India and Romania.

References

*D.T. Donovan et al. Classification of the Jurassic Ammonitina, ''in'' The Ammonoidea, M.R. House and J.R. Senior (eds); Academic Press 1981. Systematics Association Special Volume. 18
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Jurassic ammonites Ammonites of Europe {{Ammonite-stub