Potomacanthus lobatus gen. et sp. nov., a new flower of probable Lauraceae from the Early Cretaceous (Early to Middle Albian) of eastern North America.

A charcoalified fossil flower, Potomacanthus lobatus gen. et sp. nov., is described from the Early Cretaceous (Early to Middle Albian) Puddledock locality, Virginia, USA. Internal floral structure was studied using nondestructive synchrotron-radiation x-ray tomographic microscopy (SRXTM). The flower is bisexual and trimerous. The perianth consists of two whorls of tepals. The androecium has two whorls of fertile stamens. Anthers open by two distally hinged valves. The gynoecium consists of a single carpel that is plicate in the style and ascidiate in the ovary and contains a single pendant ovule. The fossil flower shares many similarities with flowers of extant Lauraceae and is unlike flowers of other families of Laurales. However, the fossil flower also differs in detail from all extant or fossil Lauraceae, particularly in configuration of the androecium. The new taxon, together with previously described but more fragmentary material from the Puddledock locality, provides the earliest fossil record of plants more closely related to Lauraceae than to any other extant family. It reveals several derived morphological characters that are potential synapomorphies among extant representatives of the family Lauraceae and contributes to the growing evidence for an early diversification of Laurales before the end of the Early Cretaceous.

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