| Abstract: | The first photographs of Cardioceratinae out of exactly defined horizons from the Latest Callovian to the Middle Oxfordian of northern Switzerland are given in this article. Most specimens were either collected in large-scale excavations, or from measured sections. The Cardioceratinae from the Cordatum Subzone are important because they are very numerous, and because particularly well-preserved specimens are abundant. Cardioceratinae of this subzone are uncommon elsewhere in Europe. All representatives of the subfamily from the Cordatum Subzone, macro- as well as microconchs, are grouped into the single genus Cardioceras. An abrupt morphological change has been recognized between the Cardioceratinae of the Densiplicatum Zone and those of the Transversarium Zone.Most of the figured specimens have been found in an incomplete sequence of thin or even condensed horizons. These beds are the distal, starved basin facies of a thick, argillaceous, shoaling-up succession in northwestern Switzerland. Sedimentologic and taphonomic methods have been used in order to work out the time sequence of sediments and ammonite faunas in condensed beds, and to arrive at a correct zonation. These methods as well as observations on the distribution of chamosite and glauconite, and the ammonite assemblages, in two coeval horizons lead us to the conclusion that the Cardioceratinae of the Cordatum Subzone in northern Switzerland lived preferentially in water less than about 100 m deep. |
