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This article presents an analysis of the affinities of legumes from the upper Cenozoic of the lower La Plata Basin (South America) with extant African genera and their implications for paleoecology and paleophytogeography. Permineralized woods, assigned to Entrerrioxylon victoriensis from the Paraná Formation (upper Miocene), Gossweilerodendroxylon palmariensis and Paraoxystigma concordiensis from the El Palmar Formation (upper Pleistocene), and Cylicodiscuxylon paragabunensis from the Arroyo Feliciano Formation (upper Pleistocene), show affinities with extant genera of the Detarioideae and Caesalpinioideae (mimosoid clade). Today, the taxa of the Detarioideae are distributed mainly in tropical regions of Africa, Central America and South America, and the monotypic genus Cylicodiscus is restricted to West Africa from Sierra Leone to Gabon. Currently, Cylicodiscus, Gossweilerodendron, and Oxystigma are not distributed in South America, which implies that in the past they were widely distributed and became extinct in this region at some point during the Pleistocene-Holocene, presumably related to the climatic changes that occurred during this time. The fossil record of the lower La Plata Basin with taxa related to the Detarioideae and Cylicodiscus supports a wider distribution during the Cenozoic as well as an ancient relationship with the tropical forests of West Africa. [ABSTRACT FROM AUTHOR]

In the La Plata Basin, indigenous populations used canoes for colonizing islands, moving people, fishing, transporting loads, and warfare. According to sixteenth century chronicles, dugout canoes were large, up to 24 m in length, and had a capacity for 40 people. In this paper, four dugout canoes recovered in La Plata River, and in the Paraná Delta, are studied. Their context of discovery, dimensions, radiocarbon dating, and the wood taxonomic identification are presented. Canoes were vital for the riverine populations that inhabited the study area since at least two thousand years ago but constitute a rare record given the low likelihood of preservation. The studied canoes measure between 10–8 m in length and 0.9–0.7 m beam. Two of the canoes were dated between 1509–1647 and 1414–1465 cal AD, 1σ. The diagnostic characters identified in the wood link all the samples to Enterolobium contortisiliquum. The use for centuries of the same species in different areas shows the importance of the type of raw material selected and reflects a shared knowledge of the properties of the dry wood: light and porous that contributes to buoyancy, easy to work, and with mechanical resistance. This, in addition to the size of the tree, up to 30 m high and 2.5 m in diameter, has favored its preference for the manufacture of hulls. These watercrafts constitute a unique cultural heritage on the pre-Hispanic naval engineering of the skilled navigators of the La Plata Basin. [ABSTRACT FROM AUTHOR]