Zygodiscaceae
Zygodiscus Bramlette & Sullivan, 1961
Optical Properties: The outer wall remains in constant extinction, while the inner wall exhibits first-order interference colours with inclined extinction lines and length-fast (−) elongation in the plan view. The optical properties of the central structure vary.
This elliptical discolith consists of three primary structural units: a central structure (bar or crossbar), a dextrally imbricated outer wall, and an inner wall, which may be dextrally or sinistrally imbricated or tangentially arranged.
The two main genera discussed in this study within the Zygodiscaeae family, Neochiastozygus and Zygodiscus, are distinguished by the following structural differences:
- Neochiastozygus has a central area spanned by a disjunct crossbar.
- Zygodiscus has a central area spanned by a disjunct bar.
Bramlette, M. N. & Sullivan, F. R. 1961, Coccolithophorids and related nannoplankton of the Early Tertiary in California. Micropaleontology 7(2): 129-188.
Hay, W. W. & Mohler, H. P. 1967, Calcareous nannoplankton from Early Tertiary rocks at Point Labau, France and Paleocene-Early Eocene correlations. Journal of Paleontology 41(6): 1505-1541.
