First Miocene record of Akaniaceae in Patagonia: fossil wood from the late Early Miocene Santa Cruz Formation.

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

Córdoba

Workshop; Reunión Anual de Comunicaciones de la Asociación Paleontológica Argentina.; 2013

Asociación Paleontológica Argentina

Akaniaceae is a family composed by two monotypic genera, Akania and Bretschneidera Today, Akania is confined to coastal and near-coastal rain forests of SE Queensland and NE New South Wales and Bretschneidera is widely distributed across southeast China and northern Vietnam. Fossil impressions attributed to Akania are known in Patagonia (Argentina) from the Laguna del Hunco and Río Pichileufú floras (La Huitrera and Ventana Formations, 51.9?47.5 Ma, Early Eocene) in Chubut Province. This contribution reports the first record of Akaniaceae from the late Early Miocene Santa Cruz Formation on the Atlantic coast of Santa Cruz Province (18?16 Ma). It consists of fossil wood with the following diagnostic features of Akaniaceae: growth rings inconspicuous, with most latewood vessels only slightly narrower than earlywood vessels; diffuse porous; vessels mainly solitary, occasionally radial multiples and clusters; perforation plates mainly simple, occasionally reticulate and rarely scalariform, with many interconnections between bars; intervessel pits bordered, minute to small; imperforate vascular tracheids; axial parenchyma vasicentric, scarce and apotracheal diffuse; vessel-ray parenchyma pits similar to intervascular pits; vessel-axial parenchyma pits scalariform; rays heterocellular, mainly multiseriate (4?6 cells wide) and rarely uniseriate, occasionally crystals in ray cells; fibers septate and non-septate, with simple to minutely bordered pits. The discovery of Akaniaceae in the Santa Cruz Formation extends the record of the taxon in South America about 30 Ma 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.