Susiea newsalemae gen. et sp. nov. (Nymphaeaceae): Euryale-like seeds from the Late Paleocene Almont Flora, North Dakota, U.S.A

Susiea newsalemae Taylor, DeVore & Pigg gen. et sp. nov. is described for distinctive seeds referable to the water lily family Nymphaeaceae from the Late Paleocene Almont Flora of central North Dakota, U.S.A. Seeds are oval to barrel shaped, 5 mm long × 3 mm wide, and have an apical operculum and a prominent lateral raphe. The outer surface of the seeds is composed of palisade, shinglelike cells 40 μm high × 150 μm wide with smooth cell margins lacking papillae. The operculum is 1 mm across and surrounded by a narrow furrow, covering the micropyle but not the hilum. The raphe and micropyle are separated by several cells. Several specimens have a small embryo cavity surrounded by a small area of presumed endosperm below the micropyle and a well-developed perisperm filling the rest of the seed cavity. Susiea seeds are most similar to those of extant Euryale but differ in features of the epidermal cells, seed coat, and raphe morphology. They also share some features with Nymphaea, Nuphar, and Victoria. Susiea appears distinct from the permineralized fossil seeds of the middle Eocene Allenbya from the Princeton chert, Nuphar wutuensis from the Eocene of China, and Nuphar cf. wutuensis from the same Almont beds. Susiea is the oldest fossil taxon of the Euryale lineage, extending the previous Oligocene record back to the Late Paleocene and documenting a significantly older age for the Euryale/Victoria clade that is clearly a derived lineage based on phylogenetic analyses of modern taxa.