Comparative paleontology and stratigraphy of Valanginian by Jeletzky J.A., Kemper E.

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By Jeletzky J.A., Kemper E.

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However, it is supposed to be derived from the Aslieria-marls (Baumberger, 1908) and so should be considerably younger than the true Euryptychites forms. g. " pavlowi Voronets 1962) are merely homoemorphic derivatives of the Stberiptychilites lineage. ites. However, the evaluation of some other cadicone representatives of PoIyptychitinae describcd from the Arctic basins remains difficult. The genus Euryptychites s. us {Neumayr and Uhlig 1881) PI. 3, fig. 2A, B; PI. 26, fig. 1, 4; PI. 27, fig. 1, 4; Figures 14a-14c.

These cadicone species are also characterized by the presence of only two lateral lobes on their siphonal side. However, they differ in the presence of at least three auxiliaries on their umbilical wall and by a relatively greater width of their saddles which are always considerably to much wider than the preceding Iobes (which are aIso relatively more narrow than their equivalents in true Euryptychites; Voronets, 1962, Figures 29-31). These Cadocerus-like representatives of Siberiptychifes also differ from true Euryptychites in a constant presence of constrictions, which were never observed in the latter genus, and a considerabIy later appearance of truIy cadicone whorl shape and proportions se(- Pseudoetrryptychites for further details).

The last preserved whorl is ornamented by trivirgatitpartitous rib bundles, which alternate with intercalated single ribs and also with intercalated dichotomous ribs, ~ h e s eintercalated ribs are not connected with the primary ribs. They may, at the most, touch the anterior secondary ribs. The remarkable density of the sculpture is, therefore, not caused by an increased number of ribs in individuaI bundIes (as happens in Prodiehotorniter species) but by a dense sequence of primitive polyptychitine bundles associated with some intercalated ribs.

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