Monetianthus mirus gen. et sp. nov., a nymphaealean flower from the Early Cretaceous of Portugal

Monetianthus mirus gen. et sp. nov. is described based on a single coalified flower from the Early Cretaceous (Late Aptian-Early Albian) Vale de Agua locality, western Portugal. The flower is actinomorphic and probably bisexual, with a perianth of nine or 10 tepals, an androecium of 20 stamens, and a syncarpous gynoecium with a partly inferior ovary of 12 carpels arranged radially around a central column. Phyllotaxis of tepals and stamens is uncertain. Nondestructive synchrotron radiation x-ray tomographic microscopy of internal structures documents laminar placentation with around six anatropous and ascending ovules in each locule. Comparison of Monetianthus with living plants indicates a clear relationship to extant Nymphaeales in particular with the Barclaya and Nymphaeoideae clade. Monetianthus thus provides evidence of crown group Nymphaeales, and probably crown group Nymphaeaceae, at a very early stage in the initial diversification of flowering plants.