Cashew nut fossils have been identified in 47-million year old lake sediment in Germany, revealing that the cashew genus Anacardium was once distributed in Europe, remote from its modern native distribution in Central and South America. It was previously proposed that Anacardium and its African sister genus, Fegimanra, diverged from their common ancestor when the landmasses of Africa and South America separated. However, groundbreaking new data in the October issue of the International Journal of Plant Sciences indicate that Europe may be an important biogeographic link between Africa and the New World.
The occurrence of cashews in both Europe and tropical America suggests that they were distributed in both North America and Europe during the Tertiary and spread across the North Atlantic landbridge that linked North America and Europe by way of Greenland before the rifting and divergence of these landmasses, explain Steven R. Manchester (University of Florida), Volker Wilde (Forschungsinstitut Senckenberg, Sektion Palaeobotanik, Frankfurt am Main, Germany), and Margaret E. Collinson (Royal Holloway University of London, UK). They apparently became extinct in northern latitudes with climatic cooling near the end of the Tertiary and Quaternary but were able to survive at more southerly latitudes.
The cashew family (Anacardiaceae) includes trees, shrubs, and climbers prominent in tropical, subtropical, and warm temperate climates around the world. A key feature is an enlarged hypocarp, or fleshy enlargement of the fruit stalk, which is a specialized structure known only in the cashew family.
The researchers examined possible fossil remains found in the Messel oil shales, near Darmstadt, Germany, which are dated to about 47 million years before the present and reveal the presence of a conspicuously thickened stalk. In four out of five specimens, this hypocarp was still firmly attached to the nut, indicating that the two were disperse
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