First South American record of Winteroxylon, Eocene of Laguna del Hunco (Chubut, Patagonia, Argentina)

BREA MARIANA; ARI IGLESIAS; WILF, P. D.

La Plata

Simposio; XVI Simposio Argentino de Paleobotánica y Palinología; 2015

Universidad Nacional de La Plata

The early-diverging angiosperm family Winteraceae today includes c. 60?90 species of evergreen trees, shrubs, and rarely epiphytes in five genera: Drimys, Pseudowintera, Tasmannia, Takhtajania, and Zygogynums.l. (including Belliolum, Bubbia, Exospermum, and Zygogynum s.s.).The family is considered to have Gondwanan origins, and its range includes Australia, New Zealand, South and Central America, Madagascar, and the Philippines, primarily in rainforest environments. Here, we report the first fossil wood record of Winteraceae from South America, found  at Laguna del Hunco (LH, La Huitrera Formation), northwestern Chubut Province, Patagonia, Argentina. Theearly Eocene lakebedsat LH preserved an outstanding compression paleoflora with high taxonomic diversity and a strong representation of Gondwanan rainforest angiosperms, conifers, and ferns. The assemblage represents the frost-free humid biome that is well known from middle latitudes of the South American early Paleogene. The wood examined here may have been transported downslope from overlying, late early Eocene strata. We assign the fossil wood to Winteroxylon Gottwald emended Poole and Francis. The diagnostic anatomical features includeabsence of growth rings; absence of vessels; tracheids rectangular in cross-section with circular pits; diffuse axial parenchyma; rays showing two distinct sizes, uniseriate and multiseriate (3?15 cells wide); rays heterocellular, containing sclereids, cells with dark contents, and oil cells. The fossil most resembles extant genera of Australasia, especially Bubbia and Tasmannia. Winteroxylon mundlosi Gottwald and Winteroxylon jamesrossi Poole and Francis differ from the new winteraceous fossil wood because they lack sclereids and oil cells in their rays.