Subdivision of the Kimmeridgian Autissiodorensis Zone (Upper Jurassic, UK)
Abstract
Ammonites hitherto included in the species Aulacostephanus autissiodorensis in fact belong to two quite separate forms that as well as being readily distinguishable morphologically have different stratigraphical ranges. A new species, Aulacostephanus camericensis, is proposed for forms which are equicostate throughout and the name A. autissiodorensis restricted to later forms that lose their ornamentation on the outer whorl. Two new subzones are proposed for the Autissiodorensis Zone: a lower Camericensis Subzone and an upper Autissiodorensis Subzone.
- Publication:
-
Proceedings of the Geologists' Association
- Pub Date:
- October 2020
- DOI:
- 10.1016/j.pgeola.2020.03.006
- Bibcode:
- 2020PrGA..131..528C
- Keywords:
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- Kimmeridgian Stage;
- Autissiodorensis Zone;
- Autissiodorenis Subzone;
- Camericensis Subzone