First Bignoniaceae liana from the Miocene of South America and its evolutionary significance.

PREMISE: Two Bignoniaceae stems with the distinctive anatomy of a liana are described from the Miocene of South America. They are the first fossil evidence of climbing habit in Bignoniaceae. METHODS: The fossil lianas are siliceous permineralizations. Transverse, tangential, and radial thin sections of the woods were prepared for study using standard petrographic techniques and observed under both light and scanning electron microscopy. RESULTS: The stems consist of wood and presumably bark (peripheral tissues). They exhibit phloem wedges, a cambial variant associated with the climbing habit in Bignoniaceae. The wood is diffuse-porous; solitary and in radial multiples vessels; alternated intervessel pitting; ray-vessel pitting with distinct borders; simple perforation plates; rays 1-3 seriate, composed of procumbent cells or body ray cells procumbent with one or two-row of upright or square marginal cells; fibers septate and non-septate, with simple to minutely bordered pits; axial parenchyma scanty paratracheal, vasicentric, septate; perforated ray cells; prismatic crystals in rays, and rays and fibers irregularly storied. The fossil stems are related to extant Dolichandra unguis-cati (L.) Miers. CONCLUSIONS: The fossils represent a new taxon, Dolichandra pacei sp. nov., which confirms the presence of a neotropical Bignoniaceae liana from the Miocene and provides the first and oldest evidence of the climbing habit in the family. Paleobotanical studies in the Mariño Formation, with the record of Bignoniaceae and Verbenaceae, and phylogenetic and biogeographical studies have great importance to understand plant evolution and diversification in South American Andes.

Guadua zuloagae sp. nov., the first petrified bamboo culm record from the Ituzaingó Formation (Pliocene), Paraná basin, Argentina.

BACKGROUND AND AIMS: The anatomical characterization and morphology of Guadua zuloagae nov. sp. (Poaceae-Bambusoideae) culm was determined. This material was collected at the Toma Vieja fossil locality, Paraná basin, Argentina. This fossil culm is the first record of Bambusoideae in sediments of the Pliocene from the Ituzaingó Formation. The studied specimen was compared with the taxa of the Bambusoideae sub-family, especially with the American woody bamboos and others taxa that have woody culms, including Arundo, Thysalonaena and Gynerium. METHODS: The material was preserved by siliceous cellular permineralization, and it was prepared for microscopic examination by surface polishing and thin sections. The morphology and anatomy of this new species were described. The estimated height, critical buckling height and safety factor were calculated on the basis of the fossil bamboo diameter using the formula of Niklas. The relationship and comparison with the nearest living relatives (NLRs) are discussed. KEY RESULTS: Well-preserved petrified culm with internodes and nodes from the Pliocene of Argentina provides the basis for the description of a new fossil bamboo, Guadua zuloagae. The results of the anatomical analysis of the fossil bamboo showed a great affinity with the extant species Guadua angustifolia and constitute the first evidence of petrified bamboo culm. CONCLUSIONS: The new fossil bamboo culm constitutes the only fossil record, preserved as permineralized by silicification, in the world. This fossil record indicates that the genus Guadua was more widespread in the past than today. Discovery of G. zuloagae allows the presence of a Bambusoideae understorey in the mixed forests described for the Ituzaingó Formation to be inferred. The climatic conditions inferred from fossil bamboo and sedimentary deposits indicate a temperate-warm, humid climate.