, Volume 43, Issue 5, pp 527-536

The evolution of the heteromorph and monomorph early cretaceous ammonites of the suborder Ancyloceratina Wiedmann

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Abstract

The relationship between the appearances of heteromorph and monomorph ammonoids and changes in the abiotic environment was studied. The correlation of these processes was examined for different intervals in the Early Cretaceous. The phylogeny of the superfamily Ancyloceratoidea Gill from the time of appearance of early heteromorphs (due to changes in ecological specialization) and the reversal process of the return to monomorph shells is examined for four superfamilies. The origin of monomorph ammonites of the superfamilies Theodoritoidea Baraboshkin et I. Michailova, superfam. nov., Douvilleiceratoidea Parona et Bonarelli, Parahoplitoidea Spath et Deshayesitoidea Stoyanow from heteromorph ancestral families Crioceratitidae Gill, Ancyloceratidae Gill, Hemihoplitidae Spath, and Heteroceratidae Spath in the superfamily Ancyloceratoidea Gill is suggested.

Original Russian Text © I.A. Mikhailova, E.Yu. Baraboshkin, 2009, published in Paleontologicheskii Zhurnal, 2009, No. 5, pp. 51–60.