Recent Topics Posters
Doria, Gabriela , Jaramillo, Carlos , Herrera, Fabiany .
Menispermaceae leaves from the Paleocene of Colombia.
The origin and processes creating the high diversity of plant species in neotropical rainforests and their floristic composition are still uncertain. The plant fossil record of the middleĖlate Paleocene (ca. 60Ė58 Ma) Cerrej√≥n flora, Guajira, Colombia, represents one of the oldest records of neotropical rain forest floras. We studied one of the most common leaf morphotypes. Fifty-seven leaf specimens were carefully examined with a focus on general morphology, venation patterns, and cuticular characteristics. Four new species assigned to the fossil-leaf genus Menispermites L. were described on the basis of an ovate leaf shape with cordate to truncate bases, actinodromous primary venation, brochidodromous secondary venation, percurrent tertiary venation, regular polygonal reticulate fourth and fifth venation, well-developed polygonal areoles, entire margin, and the presence of a fimbrial vein. Leaf morphology and venation patterns of the morphotype are remarkably similar to those of the modern lianas of the pantropical angiosperm family Menispermaceae. The presence of extant families of climbing plants as Menispermaceae has been suggested as an indicator of the multilayered structure of Cenozoic forests in contrast with Late Cretaceous forests. In El Cerrej√≥n paleoflora this multilayered structure is also indicated by the fossil record of families as Fabaceae, Lauraceae, Euphorbiaceae, Zingiberales, Araceae, and Arecaceae, present in tall canopy megathermal rain forests. Although there are very few records of fossil floras from the Late Cretaceous of tropical South America, the absence of Menispermaceae in a preliminary analysis of a new Maastrichtian assemblage (ca. 70 Ma) from central Colombia, the Guaduas flora, indicates that the Paleocene Cerrej√≥n paleoflora could be the oldest record of a multistratified tropical rain forest in the neotropics.
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1 - Wesleyan University, Earth and Environmental Sciences, 265 Church Street, Room 307, Middletown, CT, 06459, United States
2 - Center for Tropical Paleoecology and Archeology, Smithsonian Tropical Research Institute, Box 0843-03092 & # 8232, Balboa, Ancon, 34002-0948, Republic of Panama
Presentation Type: Recent Topics Poster
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM