Resumen
Three species belonging to the fern genus Ochotopteris E. Lebedev, including the new species O. lebedevii Herman et Domogatskaya, are revised, described and illustrated in this paper. The fossils come from Albian, Cenomanian, Turonian and Coniacian beds exposed at seven sites in North-Eastern Asia and Northern Alaska. These sites are located in the Cretaceous Arctic, with their palaeolatitudes ranging from 60° N to 80° N. The high endemism characteristic of the mid-Cretaceous Arctic flora is most probably due to adaptations in the globally distinctive Arctic conditions: the unique combination of temperatures, precipitation and the highly seasonal polar light regime. Being an endemic plant of the mid-Cretaceous Arctic, Ochotopteris ferns were adapted to a regional wet temperate to a wet warm temperate palaeoclimate accompanied by marked sunlight seasonality with a prolonged?up to several weeks?winter darkness and continuous summer daylight, also lasting for several weeks. The majority of the mid-Cretaceous Arctic plants were deciduous. Their predominant deciduousness was most probably due to the polar light seasonality: at the end of the growing season, some plants dropped their leaves or leafy shoots, whereas others?including Ochotopteris ferns?died back to rhizome systems.