First Pleistocene record of fossil wood of Bignoniaceae in the Americas and a comparison with the extant Tabebuia alliance and Tecomeae

Abstract

A fossil wood specimen is described from the Late Pleistocene Arroyo Feliciano Formation, Entre Ríos, Argentina. Wood anatomical characteristics indicate a close affinity with extant Bignoniaceae. The diagnostic features are: growth rings indistinct; diffuse-porous wood; vessels predominantly solitary, occasionally radial (two to four cells) and tangential multiples (two to seven cells) and in clusters; simple perforation plates; alternate, bordered and non-vestured intervessel pits; axial parenchyma apotracheal diffuse and paratracheal, vasicentric complete and incomplete, lozenge aliform and confluent; strands of two to four cells; homocellular rays; mainly uniseriate and some biseriate rays; fibres septate and non-septate; prismatic crystals in chambered axial parenchyma cells; and partially and irregularly storied structure in vessels, rays and/or parenchyma. This is the first wood fossil evidence of Bignoniaceae in the Americas; it exhibits anatomical features similar to extant Handroanthus, Parmentiera, Tabebuia and Tecoma, genera currently included in the Tabebuia alliance (Neotropical clade) and Tecomeae. This new fossil species has the potential synapomorphy (storied structure) of the Tabebuia alliance. The eco-anatomical features indicate warmer and humid climatic conditions and reconfirm the presence of tropical and subtropical forests during the Late Pleistocene. This is consistent with sedimentological and microfossil data and adds a new component to the palaeoflora of the Arroyo Feliciano Formation. Also, this fossil extends the biochron of Bignoniaceae in South America, especially Argentina, by c. 5 My, from the Miocene to the Late Pleistocene.