Fossil legume woods from the Late Miocene, Chiquimil Formation (Santa María Basin), Argentina

The legume fossil record is varied and abundant in the Cenozoic strata, especially throughout the Neogene. In northwestern Argentina there are outcrops of the Santa María Group, including the Miocene and Pliocene continental formations of the Santa María valley. These cenozoic formations contain a great variety of fossil remains (plants, invertebrates and vertebrates). In this paper, a new species of fossil wood, Paraalbizioxylon caccavariae Martínez (Leguminosae, Mimosoideae) nov. sp., from Upper Miocene Argentina, is described. The fossil wood herein described has features of the Mimosoideae subfamily, and particularly of the extant genus Albizia Durazzini and Acacia Miller. The diagnostic features present in the new fossil are: semi-ring to diffuse porous, medium to large diameter vessels, simple perforation plates, alternate and vestured intervessel pits, homogenous rays (generally 2-seriate), scanty paratracheal parenchyma, and diffuse and cristaliferous apotracheal parenchyma. The possible climatic conditions of the Chiquimil Formation were inferred from the xylological features present in the fossil wood described, suggesting a humid forest with a marked season in the localities studied.