Winged Fruits of Friisifructus aligeri gen. et sp. nov. from the Late Cretaceous of Western North America

Abstract

Premise of research. Fossil flowers and fruits with unresolved affinities among extant angiosperms may potentially represent extinct families or orders. The characterization and systematic assessments of such fossils will undoubtedly further our understanding of extinct angiosperm diversity, which is crucial for reconstructing the evolution of angiosperms in deep time. Here, we report two three-dimensionally preserved winged fruits from Campanian (∼82–80 Ma) deposits on Sucia Island, Washington State, that represent a new genus. We explore potential phylogenetic relationships of this genus relative to higher taxa across the angiosperm phylogeny. Methodology. The fossils were studied using microcomputed tomography (μCT) scanning and light microscopy. A three-dimensional reconstruction of one winged fruit was created from the μCT scans. The phyloscan method was used to assess the systematic positions of the winged fruits. Using the reconstruction, the fossil fruits were compared to extant angiosperms and extinct winged fruits to assess potential affinities. Pivotal results. The μCT scans and reconstruction of the winged fruit reveal a pentamerous perianth, five pairs of fin-wings, two whorls of persistent stamens, five semicircular nectary pads, an inferior unilocular ovary, and a style with three stylar branches. Phyloscan analyses recover the winged fruits within the rosid clade, but they cannot be assigned to any extant family or order within the group because of differing floral and fruit morphologies. Conclusions. The winged fruits are assigned to Friisifructus aligeri gen. et sp. nov. This new genus and species add to the diversity of winged fruits from the Cretaceous, which are relatively uncommon. Moreover, the unique morphology of Friisifructus indicates that this genus may belong to an extinct family of rosids.