First record of Styracoxylon (Styracaceae) from Southern Hemisphere: Arroyo Feliciano Formation (Upper Pleistocene), Entre Ríos, Argentina

Abstract

A new species, Styracoxylon thyllosum sp. nov., is described from the Upper Pleistocene Arroyo Feliciano Formation of the Gualeguay Basin in eastern Argentina. It is the first unequivocal record of the Styracoxylon Burgh 1978 in South America and was previously known only from the Pliocene of the Rhine area, Netherlands. This fossil specimen was recovered in the Consorcio Paso Sociedad Locality (Federal, Entre Ríos, Argentina). The new fossil species is characterized by growth ring boundaries distinct, with diffuse-porous wood. Vessels are mostly in radial multiples of 2?6 elements, occasionally solitary and rarely in clusters. Tylosis is abundant. Perforation plates are usually scalariform (5?20 bars) and rarely simple. Intervessel pits are small, bordered, alternate to opposite. Rays are frequently 2?4 (6) seriate and rarely uniseriate, heterocellular, and of two distinct ray sizes. Fibres are non-septate, with distinctly bordered pits, and rounded to hexagonal in outline. The axial parenchyma is apotracheal diffuse and diffuse-in-aggregates, and in strands of 8?12 cells.Vascular tracheids possibly present. Wood anatomical features suggest a relationship with Styracaceae, and the fossil specimen shows affinity with the extant genus Styrax Linnaeus.