Dalbergieae (Fabaceae) Samara Fruits from the Late Eocene of Colombia

Premise of research.Species richness of Leguminosae (Fabaceae) is highest in the Neotropics today, but the fossil evidence of the family from this region remains sparse. The study of a fossilized indehiscent winged fruit (samara) from a recently discovered flora from the late Eocene Esmeraldas Formation in Colombia increases our understanding of the fossil record of Leguminosae from the Neotropics and sheds light on the evolution and ecology of this emblematic angiosperm family.Methodology.Plant fossils were collected from a new locality in the late Eocene Esmeraldas Formation. Fifteen fossilized samara fruits were described and compared to fossil and extant angiosperm fruits based on herbarium collections and literature. Taxonomic affinities of the fossil fruits within the clade Dalbergieae (Papilionoideae, Fabaceae) were evaluated by a combined analysis of morphological and molecular data.Pivotal results.A new fossil fruit, Luckowcarpa gunnii gen. and sp. nov., is described and associated with the Pterocarpus clade (Dalbergieae) based on the presence of two-seeded unicarpellate samaras with a proximal seed chamber and a style remnant at the distal end of the wing. Luckowcarpa gunnii represents the earliest fruit fossil record of the Dalbergieae clade.Conclusions.The phylogenetic position of L. gunnii, nested within the clade Dalbergieae, supports the hypothesis that legume diversification occurred early in the Tertiary in low latitudes and suggests that this fossil taxon could have been adapted to tropical dry forest ecosystems.