Anatomically preserved seeds of Corylopsis (Hamamelidaceae) from the miocene of Yunnan, China, and their phytogeographic implications

Lignitized seeds from the Early to Middle Miocene of Yunnan Province, southwestern China, are assigned to the genus Corylopsis (Hamamelidaceae) on the basis of morphological and anatomical details. The seeds are ovoid, with a conspicuous sunken, asymmetrical hilar scar on the ventral side and a large hilar facet on the dorsal side. The seed coat is composed of a massive testa, consisting of exotesta, mesotesta, and endotesta, and a tegmen consists of one layer of columnar cells. A new species, Corylopsis tengchongensis Zhao et Li sp. nov., has been erected to accommodate them. The abundance of these seeds suggests that they represent plants that probably grew in a nearby swampy environment. While Corylopsis is an eastern Asian genus today, the fossil record documents that the genus had a wide geographical distribution during the Tertiary in Europe, North America, and Asia. The absence of Corylopsis in post-Eocene floras of North America and in post-Pleistocene floras of Europe suggests that the range of its distribution was reduced in response to the climatic cooling of the Eocene/Oligocene boundary and the Pleistocene glaciations, respectively. The new species confirms the unequivocal presence of Corylopsis in China in the Miocene. As the earliest evidence of Corylopsis in eastern Asia, these fossil seeds might shed light on the migration of this genus.