Astroniumxylon, Schinopsixylon and Parametopioxylon n. gen. fossil woods from Upper Cenozoic of Argentina: Taxonomic revision, new taxon and new records

This paper presents new descriptions of Anacardiaceae fossil woods from
the Ituzaingó Formation (late Cenozoic) at the Toma Vieja, Curtiembre, and
Arroyo El Espinillo localities, Argentina. We describe eight silicified
woods assigned to four different species in three genera, one of which,
Parametopioxylon crystalliferum n. gen. n. sp., is new. Similarities
between these three genera and the six Anacardiaceae species previously
recorded from the late Cenozoic in northeastern Argentina are investigated
using multivariate analysis techniques (correspondence and cluster
analysis). Our study is based on thirty-three characters scored for
seventeen fossil specimens (ten Astroniumxylon Brea, Aceñolaza et Zucol
2001, five Schinopsixylon Lutz 1979 and two Parametopioxylon n. gen.) and
four extant species (Astronium balansae Engl., Astronium urundeuva Engl.,
Schinopsis balansae Engl. and Metopium sp.). Our main goal is to determine
the wood anatomical features useful for distinguishing among these
species. The results of the multivariate analyses support the previous
classification where Schinopsixylon is distinguished from Astroniumxylon
by having exclusively paratracheal axial parenchyma, ≥30% multiseriate
rays, and multiseriate rays that are ≥5 cells wide and commonly 301–400 µm
in height. Additionally, we propose that Schinopsixylon heckii Lutz 1979
is synonymous with S. herbstii Lutz, 1979. A diagnostic key for the fossil
species studied is given. Wood anatomy of Anacardiaceae fossil woods from
Argentina (late Cenozoic) suggests a warm dry to semi-humid climate for
this region supporting previous studies.