Freshwater centric diatoms from Middle Miocene deposits of the Khanka Depression, Primorye Territory (Far East of Russia)

The centric diatom flora from the Middle Miocene deposits of the Khanka Depression of Primorye (Far East of Russia) was in detail studied. The centric diatoms were presented by 10 species and intraspecies taxa belonging to four genera (Aulacoseira Thwaites, Alveolophora Moiseeva et Nevretdinova, Ellerbeckia Crawford, Melosira Agard) and three orders (Aulacoseirales, Paraliales and Melosirales). A detailed study with the use of LM and SEM allowed us to establish the high morphologic variability of the predominant representatives of the genus Aulacoseira. The diagnoses for the Alveolophora tscheremissinovae, Ellerbeckia kochii, Melosira undulata species were supplemented. The comparison of the taxonomic compositions of the centric diatoms from the Khanka complex with the even-aged complexes from other regions has shown the wide spreading of the genus Aulacoseira taxa in the freshwater bodies during this time period.