Nitellopsis (Charophyta) from the Miocene of northern Thailand

Charophyte gyrogonites from two Miocene sites in northern Thailand are studied and compared for population variation. Morphometrical differences between the two populations, determined as Nitellopsis merianii and N. meriani globula, correspond to variation at the interpopulation level and do not justify the distinction of two separate species as made by previous authors. The first exhaustive synonymy for both taxa is listed. Morphological differences can be attributed to environmental differences as reflected by distinct lithologies of the samples concerned. The eurasian character of N. merianii is underlined through its biogeographical distribution in China. The flora is in accordance with the early Middle Miocene age (16–14 My) previously published for vertebrate faunas from the same sites.