RUPRECHTIA IN THE MIOCENE EL CIEN FORMATION, BAJA CALIFORNIA SUR, MEXICO

Fossil woods from the El Cien Formation have yielded important information on the taxonomic composition and climate of a flora established in the west coast of Mexico during the Miocene. This report of a new genus and species, Ruprechtioxylon multiseptatus Cevallos-Ferriz, Martinez Cabrera et Calvillo-Canadell, is based on woods with the following combination of features: vessels solitary and in radial multiples of 2-3; vestured, alternate, oval to polygonal intervessel pits; vessel-ray and vessel-parenchyma pits similar in size to intervessel pits, but with slightly reduced to reduced borders; 2-5 septa per fibre; scanty paratracheal, unilateral and vasicentric axial parenchyma; uniseriate homocellular rays, occasionally locally biseriate; crystals in fibres. The presence of Ruprechtioxylon (Polygonaceae) in the El Cien Formation confirms that plants of lineages growing today under contrasting climates lived together in the past. This record adds a new species to the growing list of Neotropical taxa that were present in Mexico prior to the great Plio-Pleistocene exchange of biota in the Americas.