Fossils in thin section

Trilobites in thin section

Long, sinuous shell sections, often ending in a recurved 'shepherd's crook'. Walls are generally under 1 mm thick, with calcite crystals perpendicular to the wall. The fabric looks homogeneous in plane light and shows sweeping (undulose) extinction under crossed polars. The hook resembles an ostracod's edge but is larger.

Age: Trilobites went extinct at the end of the Permian.

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All fossil groups Carbonate classification