separate genus, but other authors find the morphological differences too small to legitimate that status. Support for both opinions can still be found all over scientific and colloquial sources. Phylogeny Genetic analysis suggest that three monophyletic groups can be identified. C. natans turns out to be sister to all other species. It also turns out that C. leptosepala is the sister of all Southern Hemisphere species and should be moved into the Psychrophila group. Within that section the New Zealand and Australian species form one cluster, C. appendiculata and C. dionaeifolia form a second cluster, while the third South American species, C. sagittata, is sister to both these clusters. The remaining Northern Hemisphere species, C. palustris and C. scaposa make up the new content of the Caltha group. This suggests the genus originates in the Northern Hemisphere, and dispersed from North America to South America and from there to New Zealand and Australia. Relations between the species are represented by the following tree. Reassigned species Some species that were described as Caltha have been reassigned to other genera later on. C. bisma = Aconitum undetermined sp. C. camschatica = Oxygraphis glacialis C. codua = Aconitum undetermined sp. C. glacialis = Oxygraphis glacialis C. hiranoi = Ranunculus ficaria C. nirbisia = Aconitum undetermined sp. C. officinalis = Calendula officinalis Etymology The generic name Caltha is derived from the (kalathos), meaning "goblet", and is said to refer to the shape of the flower. Distribution Caltha species are found in the cold and temperate regions of the Northern Hemisphere, the Andes and Patagonia, and alpine areas in Australia and New Zealand. It is absent from lower altitudes in the tropics and subtropics, in Africa, on Greenland and some other arctic island, from Antarctica and subantarctic islands and from oceanic islands. C. natans occurs in Siberia and North America, but not in Europe. C. palustris has the widest distribution and is present in the cold and temperate regions of the Northern Hemisphere, but cannot be found in the Western United States. C. scaposa is an alpine species with a limited distribution on the south-eastern rim of the Highland of Tibet. Caltha leptosepala occurs in western North-America from Alaska to California and Colorado. C. sagittata is another species that occurs in moist alpine meadows, in this case from Colombia to Tierra del Fuego, growing at less altitude further from the equator. C. appendiculata occurs in