First Miocene record of Akaniaceae in Patagonia (Argentina): a fossil wood from the Early Miocene Santa Cruz Formation and its palaeobiogeographical implications.

BREA, M.; ZUCOL, A. F.; BARGO, M.S.; FERNICOLA, J.C.; VIZCAÍNO, S.

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 183 p. 334 - 347

0024-4074

Today, the Akaniaceae are confined to SE Queensland, NE New South Wales, southeast China and northern Vietnam. Akanioxylon santacrucensis gen. nov. et sp. nov. is described as the first fossil wood of Akaniaceae from the Early Miocene Santa Cruz Formation (~18?16 Ma; Burdigalian) on the Atlantic coast of Santa Cruz Province, Argentina. The diagnostic features are: growth rings inconspicuous, with most latewood vessels only slightly narrower than earlywood vessels; diffuse porous wood; mainly solitary vessels, occasionally radial or tangential multiples and clusters; mainly simple, occasionally reticulate and rarely scalariform with many interconnections between bars perforation plates; bordered, minute to small intervessel pits; axial parenchyma scanty paratracheal and apotracheal diffuse; vessel-ray parenchyma pits with much reduced borders to apparently simple; vessel-axial parenchyma pits scalariform or transitional; mainly multiseriate (4?6 cells wide) and rare uniseriate rays, heterocellular, occasionally crystals in ray cells; septate and non-septate fibers with simple to minutely bordered pits. These features resemble the extant Akania Hook. F. and Bretschneidera Hemsl. The eco-anatomical analysis suggests that this fossil wood grew under temperate to warm-temperate and semiarid climatic conditions. This record of wood Akania/Bretschneidera-like in South America reinforces the existence of an old relationship with the Australasia flora. The discovery of Akaniaceae in the Santa Cruz Formation extends the record of the taxon in South America about 30 Ma and 10 degrees south latitude, and suggests that the family was widespread in Patagonia as a component of forests developed in a frost-free humid biome in South American middle to high latitudes.