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Which fossil marks the beginning of the Devonian System at the Klonk section?
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Silurian Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the middle part of the Silurian Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The beginning of the Devonian System at the Klonk section in the Czech Republic is marked by the first occurrence of the graptolite species Monograptus uniformis.12
This horizon, which defines the base of the Monograptus uniformis biozone, serves as the international standardāoften referred to as a "golden spike"āfor the Silurian-Devonian boundary. While this graptolite taxon is the primary marker, the boundary is further reinforced by associated conodont and trilobite taxa.2