Fossil wood of the Mimosoideae from the Early Paleocene of Patagonia, Argentina
BREA, M., ZAMUNER, A.B., MATHEOS,S., IGLESIAS, A. Y ZUCOL, A.F.
Taylor & Francis
Lugar: Wollongong (Australia); Año: 2008 vol. 32 p. 431 - 445
An anatomically preserved mature stem from the Salamanca Formation (early Paleocene) at Palacio de Los Loros locality, central Patagonia, Argentina, is described and assigned to Paracacioxylon frenguellii sp. nov. The material was preserved by siliceous permineralization and shows features of the secondary xylem typical of subfamily Mimosoideae. This species represents the oldest record of the genus and of the Leguminosae along the western border of Gondwana, and is the world is second oldest record for wood of subfamily Mimosoideae. The species is characterized by ring-porous to semi-ring-porous, vessels that are solitary, multiples of 2-4 and clustered in, simple perforation plates, alternate and vestured inter-vessel pitting, homocellular 1-6 seriate rays, tyloses, crystals and diffuse apotracheal, vasicentric paratracheal and confluent axial parenchyma. Paracacioxylon frenguellii has anatomical similarities to Acacia Muller. The presence of Paracacioxylon frenguellii associated with pulvinate leaves suggests that the legumes might have been a component of mesothermal forests developed along the western margin of the Golfo San Jorge Basin during the early Paleocene.