Multivariate analysis of Lower Cretaceous monosulcate pollen from central-western Argentina

Abstract

Monosulcate pollen grains are an important component of the Mesozoic palynofloras around the world. These type of grains are produced by several groups of plants and because of the morphological similarities among them, their taxonomic determination is difficult. Currently, there is scarce information about morphological differences of monosulcate pollen grains and this makes their botanical affinity in fossil specimens challenging. In this work, we analyzed statistically the morphological features of monosulcate fossil pollen grains recovered from six palynological assemblages from the Lower Cretaceous Lagarcito Formation of central-western Argentina. We used our own fossil dataset and data from the description of monosulcate pollen grains published from Cretaceous cycadalean in situ male cones from Patagonia. Furthermore, morphological variables from selected living species were added to support the analysis. According to our results, two main groups with clear morphological features were characterized among fossils. The use of an extant dataset allowed us to support the exine sculpture as an important variable when characterizing fossil pollen grains. Finally, our fossil dataset showed similarities with the in-situ pollen grains from the cycadalean cone species Androstrobus munku and Androstrobus patagonicus. This work is the first attempt to identify different morphological types among fossil monosulcate pollen grains recovered from the Lagarcito Formation of central-western Argentina. Our results will contribute to elucidate morphological variations in fossil pollen grains and may improve future taxonomic studies.