Zingiberalean fossils from the late Paleocene of North Dakota, USA and their significance to the origin and diversification of Zingiberales

The Zingiberales, including the gingers (Zingiber), bananas (Musa) and ornamental flowers (Strelitzia, Canna, and Heliconia) are a diverse group of monocots that occupy the tropics and subtropics worldwide. The monophyly of the order is well supported, although relationships between families are not well resolved. A rapid divergence of the Zingiberales has been proposed to explain the poor resolution of paraphyletic families in the order, and direct fossil evidence shows members of both of these lineages of Zingiberaceae and Musaceae were present by the Late Cretaceous. Comparisons of the fossils with extant relatives and their systematic placement have been limited because variation within modern taxa is not completely known. The current study focuses on describing zingiberalean fossil material from North Dakota that includes seeds, leaves, buds, adventitious roots and rhizomes. A survey of extant zingiberalean seeds was conducted, including descriptions of those for which data were previously unknown, in order to resolve the taxonomic placement of the fossil material. Upon careful examination, anatomical characters of the seed coat in fossil and extant seeds provide the basis for a more accurate taxonomic placement of the fossils and a better understanding of character evolution within the order.