Mite houses, or acarodomatia, are found on the leaves of over 2,000 living species of flowering plants today. These structures facilitate tri-trophic interactions between the host plant, its fungi or herbivore adversaries, and fungivorous or predaceous mites by providing shelter for the consumers. Previously, the oldest acarodomatia were described on a Cenozoic Era fossil leaf dating to 49 million years in age. Here, we report the first occurrence of Mesozoic Era acarodomatia in the fossil record from leaves discovered in the Late Cretaceous Kaiparowits Formation (76.6–74.5 Ma) in southern Utah, USA. This discovery extends the origin of acarodomatia by >25 million years, and the antiquity of this plant–mite mutualism provides important constraints for the evolutionary history of acarodomatia on angiosperms.

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