Spirematospermum wetzleri (Heer) Chandler (Zingiberaceae) from the Miocene of Weichang, Hebei Province, North China and the phytogeographic history of the genus

Spirematospermum is a well-known extinct zingiberalean taxon, characterized by trilocular capsules containing many distinctive, spirally striate and arillate seeds. It is frequently found and studied in European Neogene carpological floras, but is scarcely represented in East Asia floras. In this work we recognize a new fossil record of Spirematospermum wetzleri (Heer) Chandler based on the capsules and seeds from the Miocene of Weichang, Hebei Province, North China. These fossils represent the first record of the species in the Miocene of China. Fossil data indicate that Spirematospermum probably originated in the Late Cretaceous of North America or Central Europe. The genus still existed in the Paleocene of North America, but became extinct after that time. However, the genus successively survived in Europe from the Eocene to Pliocene, and flourished luxuriantly during the Oligocene to Miocene. As there was Turgai Strait between Europe and Asia during the Eocene, the genus did not spread to Central Asia and West Siberia until the strait closed in the late Eocene/early Oligocene, and further expanded eastwardly to eastern Siberia, Russia, northern China and central Japan during the Miocene, but became extinct in Asia after the Miocene. The genus contracted its distribution to Europe in the Pliocene, and afterwards it became extinct in the world.