Pollen with viscin threads from the Late Cretaceous and Paleocene, Merida Andes, western Venezuela

Fossil pollen exhibiting viscin threads are reported from Upper Cretaceous and Paleocene deposits in western Venezuela. The sediments were deposited in a marginal marine environment in an area presently occupied by the northern flank of the Venezuelan Andes. The palynofloras are well preserved and diverse and provide insight into the ancient vegetation of Venezuela. Pollen-bearing viscin threads from the Upper Cretaceous Mito Juan Formation are assigned to the genus Colombipollis Sarmiento Perez 1994. The pollen grains are tri(col)porate, normally quite smooth, and most often viewed in an oblate (flattened) state. The viscin threads are on the proximal and distal sides of the pollen and vary in length; they appear to have a simple morphology unlike the complex, rope-like threads seen on pollen of the Onagraceae and some other angiosperm families. All observations to date are made using a standard light microscope but more morphological detail could be revealed using scanning electron microscopy. The pollen exhibiting viscin threads from the Paleocene Los Cuervos Formation are clearly related to onagraceous types and are assigned to the genus Corsinipollenites Nakomen 1995. The pollen is triporate and the viscin threads originate from the polar regions of the pollen. They resemble pollen reported from Eocene to Miocene deposits in the southern hemisphere (Australia, New Zealand) although are smaller in overall dimensions. The Venezuelan pollen reported in this paper post date the earliest record of viscin threads in the Turonian of the eastern United States. They represent the first reported forms from the South American region. In modern plants the presence of viscin threads has been related to the development of highly specific plant-pollinator relationships; their presence in the Late Cretaceous and Paleocene in Venezuela may help constrain the timing of the origin of certain insect groups in this area.