Calcium carbonate crystals in a distinctive structure that reveals that this ancient eggshell comes from a prehistoric flamingo egg from the Miocene epoch (23.03–5.33 million years ago). It is calcium carbonate that makes eggshells hard.

Visualised using electron backscatter diffraction by Dr Gerald Grellet-Tinner, the Field Museum, Chicago and Dr Pat Trimby, University of Sydney.

Size: about 0.6 millimetres thick.

The egg came from a nest at the Miocene site of Bardenas Reales – the oldest known nest built by a true bird. Australia had flamingos in the Miocene but they died out when the climate changed. Scientists can use information held in current and fossilised eggshells to understand how the birds respond to climate change. Dr Xabier Murelaga from the University of the Basque Country and Dr Juan Larrasoaña at the Instituo Geológico y Minero de España were also involved in this work.

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