Menispermaceae from the Cerrejon Formation, middle to late Paleocene, Colombia

Abstract

The origin and processes creating the high diversity of plant species in neotropical rain forests and their floristic composition and multistratitified forest structure are still uncertain. Here, we studied one of the most common leaf morphotypes of the Cerrejon flora (middle-late Paleocene, ca. 60-58 Ma), Guajira, Colombia, that contains one of the oldest records of neotropical rain forest floras. Fifty-seven leaf specimens were carefully examined with a focus on general morphology, venation patterns, and cuticular characteristics. The analysis allowed us to recognize four new species that were assigned to the fossil-leaf genus Menispermites 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. This set of characters suggests a possible affinity with the pantropical angiosperm family Menispermaceae. The predominantly climbing habit of this family suggests that the Cerrejon Paleocene tropical rain forest was already multistratified. These findings represent the earliest record for the family in northern South America.