Fossiilseid

Fossiilseid is the Estonian term for fossils, referring to the preserved remains, impressions, or traces of once-living organisms from past geological time. Fossils encompass both body fossils and trace fossils. They are typically found in sedimentary rocks and occasionally in amber, ice, tar, or mineral nodules.

Formation and preservation: Fossilization requires rapid burial and conditions that limit decay. Common preservation modes include permineralization (minerals fill pore spaces in originally organic material), recrystallization or replacement of original material, carbonization (dark, planar compression of organic matter), and the formation of external or internal molds and casts. Trace fossils record activities such as footprints, burrows, feeding marks, and feces (coprolites).

Types and biases: Body fossils preserve physical remains such as bones, teeth, shells, or impression fossils. Trace fossils preserve evidence of behavior. The fossil record is biased toward organisms with hard parts and those living in environments conducive to rapid burial, such as rivers, deltas, and shallow seas. Soft-bodied organisms are underrepresented.

Dating and interpretation: Fossils are dated using relative methods, including stratigraphic position and index fossils, and absolute (radiometric) dating when suitable materials are available. Together, these methods reconstruct timelines of evolution, climate, and biogeography.

Significance: Fossils provide direct evidence of ancient life, its diversity, morphology, and ecology, and illuminate major transitions such as the emergence of multicellular life, vertebrates, and plants. They also help reconstruct ancient environments and climatic conditions.