The morphology, systematic position and inferred biology of Spirematospermum — An extinct genus of Zingiberales

A new extraordinary mass occurrence of Spirematospermum wetzleri capsules from the Middle Miocene of Ponholz (Germany) allowed comprehensive studies of this intriguing Zingiberalean species to be carried out. Parietal placentation, flower remains and a dual generative reproductive strategy by seed dispersal and capsule abscission were found. The petiole anatomy and a putative pollen grain of S. wetzleri are described. Fossil rhizomes and Zingiberales-type leaves are associated. Phytoliths of seeds, leaves, and rhizome sheaths are described and compared to extant Zingiberales phytoliths. Analysis of characters places the fossils as sister to the clade of Musa and Ensete in the Musaceae. We propose a new Musaceae subfamily for Spirematospermum. Cluster analysis of 81 Eurasian Palaeogene and Neogene floras with Spirematospermum identified water-associated habitats and divergent plant associations distinctly changing from the Oligocene to the Pliocene. The extraordinary longevity of S. wetzleri is explained by its broad ecological amplitude. Its wide palaeobiogeographic and stratigraphic distributions are summarized and correlated with the Cretaceous or Paleocene North American extinction event and the final Pliocene Eurasian extinction.