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Description
In this picture we begin our coverage of the next family of the superfamily Turrilitoidea ancyloceratine ammonites. The Nostoceratidae had to contain without question the most bizarre of the heteromorph ammonites of these This first page sees the least odd of the group, with several more basal genera that had simple loosely coiled but otherwise relatively normal shells (Such as Exiteloceras). Others had helical shells combined with an oxbow like extension (like Ainoceras). Others had weird loosely coiled helical shells such as (Bostrychoceras). As a group the family emerged in the Late Cretaceous and ended with the famous asteroid impact that ended the period. While some of these early forms were likely decent swimmers of the proto pacific (Eubostrychoceras). The others were likely unable to swim efficiently at all and due to this are hypothesized to have lived in two niches. One says they were passive floaters others say they were bottom dwellers. Personally, I think it's not an either-or question as it is likely there were species in both places.
Left to Right:
Top Row: Ainoceras, Anaklinoceras minutum, A. reflexum
Second Row: Axonoceras, Bostrychoceras, Exiteloceras
Bottom Row: Eubostrychoceras, Jouaniceras, Hyphantoceras

Description
In this picture we begin our coverage of the next family of the superfamily Turrilitoidea ancyloceratine ammonites. The Nostoceratidae had to contain without question the most bizarre of the heteromorph ammonites of these This first page sees the least odd of the group, with several more basal genera that had simple loosely coiled but otherwise relatively normal shells (Such as Exiteloceras). Others had helical shells combined with an oxbow like extension (like Ainoceras). Others had weird loosely coiled helical shells such as (Bostrychoceras). As a group the family emerged in the Late Cretaceous and ended with the famous asteroid impact that ended the period. While some of these early forms were likely decent swimmers of the proto pacific (Eubostrychoceras). The others were likely unable to swim efficiently at all and due to this are hypothesized to have lived in two niches. One says they were passive floaters others say they were bottom dwellers. Personally, I think it's not an either-or question as it is likely there were species in both places.
Left to Right:
Top Row: Ainoceras, Anaklinoceras minutum, A. reflexum
Second Row: Axonoceras, Bostrychoceras, Exiteloceras
Bottom Row: Eubostrychoceras, Jouaniceras, Hyphantoceras