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

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

Botanical Journal of the Linnean Society

The Linnean Society of London

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

1095-8339

Today, Akaniaceae are confined to south-eastern Queensland, north-eastern New South Wales, south-easternChina, and northern Vietnam. Akanioxylon santacrucensis gen. and sp. nov. is described as the first fossil wood ofAkaniaceae from the early Miocene Santa Cruz Formation (c. 18?16 Ma; Burdigalian) on the Atlantic coast of SantaCruz Province, Argentina. The diagnostic features are growth rings inconspicuous, with most latewood vessels onlyslightly narrower than earlywood vessels; diffuse porous wood; mainly solitary vessels, occasionally radial or tangentialmultiples and clusters; mainly simple, occasionally reticulate and rarely scalariform with many interconnectionsbetween bars perforation plates; bordered, minute to small intervessel pits; axial parenchyma scanty paratrachealand apotracheal diffuse; vessel-ray parenchyma pits with much reduced borders to apparently simple; vessel-axialparenchyma pits scalariform or transitional; mainly multiseriate (four to six cells wide) and rare uniseriate rays,heterocellular, occasionally crystals in ray cells; septate and non-septate fibres with simple to minutely borderedpits. These features resemble the extant Akania Hook.f. and Bretschneidera Hemsl. The eco-anatomical analysissuggests that this fossil wood grew under temperate to warm-temperate and semi-arid climatic conditions. Thisrecord of Akania/Bretschneidera-like wood in South America reinforces the existence of an old relationship with theAustralasia flora. The discovery of Akaniaceae in the Santa Cruz Formation extends the record of the taxon in SouthAmerica c. 30 Ma and 10°S in latitude and suggests that the family was widespread in Patagonia as a component offorests developed in a frost-free humid biome in South American at mid to high latitudes.