Silurian noncalcified macroscopic algal fossils from the Kalana Lagerstätte, Estonia

Humanity’s knowledge of organisms our planet’s past organisms, come from fossil record, which is predominated by animals who possessed some kind of skeleton. Soft-bodied organisms, like invertebrates without mineralized tissues or non-calcified algae have only rarely been preserved as fossils. The Kalana (Otisaare) quarry in Central Estonia has revealed unique algal fossils, which show anatomical details and species diversity, which widen our knowledge about marine ecosystems in the Silurian times. The aim of the present research was to study systematics of the algal fossils in Kalana, to give an overview of algal fossils in Estonia and the whole world and to interpret the environment conditions (water depth, temperature, bottom conditions) where the algae lived and were buried. Among the species described in the present thesis, two (Palaeocymopolia silurica and Kalania pusilla) belong to green algal (Chlorophyta) order Dasycladales. The third species described from the Kalana Lagerstätte is Leveilleites hartnageli, which according to external morphology and position of reproductive structures belongs to red algae (Rhodophyta), class Floridophyceae. The algal thalli were buried in situ, probably in a lagoonal environment with normal salinity, which was protected from wave action and where water depth did not exceed 15 meters and temperature was around 20 °C. In addition to the Kalana quarry, in Estonia, noncalcified algal material has been discovered from some other quarries and drillcores, proving that noncalcified algae were widespread all over the present territory of Estonia in the early Silurian marine environments ca. 440 Ma. World-wide, 37 localities with noncalcified macroscopic algal fossils have been described from the Silurian strata, most of them have been discovered from Baltica and Laurentia palaeocontinents