FOSSIL LIANAS FROM THE MIOCENE OF PANAMA AND THEIR PALEOENVIRONMENTAL IMPLICATIONS

Fossil lianas have been used as indicators of warm, wet paleoclimates; but recent studies show that extant liana diversity and abundance are related to seasonality, disturbance regime, and pCO₂ in predictable ways. Therefore, the presence of lianas in Cenozoic fossil assemblages can now be used to provide more precise information for paleoenvironmental reconstructions. Here, we report the presence of liana fossils from the 19Ma fluvial-delatic deposits of the Cucaracha Formation in Panama. So far, we have identified at least 5 distinct liana morphotypes based on stem anatomy; and several more are represented by fossil fruits. An analysis of growth rings in co-occurring fossil woods suggests a short dry season. Oxygen isotope data from co-occurring mammal teeth suggest minimal seasonality. During the early Miocene, pCO₂ levels were similar to modern, or slightly elevated. However, there are several potential sources of natural disturbance that could explain the high diversity of lianas in the Cucaracha Formation including volcanism, megafaunal disturbance, and fluvial processes. Therefore, we interpret the lianas from the Cucaracha as indicators of disturbance in a tropical forest community with a short dry season.