Morphological variability and method of opening of the Devonian acritarch Navifusa bacilla ( Deunff, 1955) Playford, 1977

The morphological variability of the genus Navifusa Combaz et al. 1967ex Eisenack 1976 has been investigated within three populations from a Lower Devonian section at Císařská rokle, near Srbsko (Barrandian area, Czech Republic). All observed specimens can be attributed to the single species Navifusa bacilla. Differences in size ratio are interpreted ecologically, initiated by sea level changes. The method of cyst opening of this species is discussed, as it allows recognition of different phases of excystment.