MICROLOBIUSXYLON PARANAENSIS GEN. ET SP NOV (FABACEAE, MIMOSOIDEAE) FROM THE PLIOCENE-PLEISTOCENE OF ITUZAINGO FORMATION, PARANA BASIN, ARGENTINA

A fossil wood with Fabaceae affinity from the Pliocene-Pleistocene sediments of Ituzaingo Formation is described. The silicified wood was collected at the Toma Vieja fossil locality, Parana Basin, Argentina. The relationship and comparison with the nearest living relatives (NLRs) are discussed. Wood anatomical characters suggest an affinity with the genus Microlobius C. Presl. In South America, the genus Microlobius occurs in Brazil, Bolivia (Santa Cruz), Argentina (Chaco and Formosa) and Paraguay and is an important extant element of the Paraguay-Parana system. The presence of this fossil in the Ituzaingo Formation supports the idea that the morphogenus Microlobiusxylon might have been an important component of seasonally dry tropical forests (SDTFs) during the Pliocene-Pleistocene. Today, this forest type has a relict distribution, occurring in isolated localities in the north of Argentina, southeast of Bolivia and Brazil, but in the past were more widespread to the east and south in South America. The presence of Microlobiusxylon paranaensis gen. et sp. nov. would indicate a temperate-warm climate during the Pliocene-Pleistocene.