CONICET | Buscador de Institutos y Recursos Humanos

In the last years, the number of Anacardiaceae fossil woods found in the upper Cenozoic of northeastern Argentina has increased significantly. A new analyses and delimitation of diagnostic characters was proposed because some fossil taxa were based on non-informative features probably because this family has homogeneous wood anatomy, hindering the delimitation of the fossil species common in the region. The aim of this study is to determine taxonomically relevant characters, anatomical variability and relationships among Anacardiaceae species, found in Ituzaingó, Paraná, El Palmar and ?Salto Chico? formations. Correspondence and Cluster analyses were used in order to establish the taxonomic limits and the diagnostic characters in fossil taxa; we also propose a taxonomic key. This taxonomic revision was based on seventeen fossil specimens (ten of Astroniumxylon Brea, Aceñolaza et Zucol, 2001, five of Schinopsixylon Lutz 1979 and two of a new genus and species) and four extant species (Astronium balansae Engl., Astronium urundeuva Engl., Schinopsis balansae Engl. and Metopium sp.). Thirty-three anatomical wood variables were defined (twenty-one double-state and twelve multi-state characters). Anacardiaceae genera and species included in this study are clearly distinguished. Nevertheless, species of Schinopsixylon (S. heckii Lutz 1979 and S. herbstii Lutz 1979) are not clearly segregated. Characters that allowed separating Schinopsixylon from Astroniumxylon are the presence of mostly 4?10 seriate rays, commonly ≥6 cells wide, 301?400 μm in height, and axial parenchyma exclusively paratracheal. These multivariate analyses contribute to assure the taxonomic placement of specimens, especially when some characters are unpreserved or not clearly observed.