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A new scheme of Late Triassic palaeophytogeographic regionalization of China is put forward on the basis of three principles given as follows:1. The palaeophytogeographic regionalization should be based on the characters of the various floras themselves. These characters include the types of the dominant floras, compositional patterns of various communities and existence of dominant genera or those genera and species characteristic of a region.2. The palaeogeographic positions of the floras in geologic time should be considered.3. The distribution of the floras was influenced in three directions——latitudinal, longitudinal and vertical——in geological time.Formerly, a number of Chinese palaeobotanists based the palaeophytogeographic regionalization only on the factor of latitude, and neglected the characters of the floras themselves and the effect of their three-directional zonation. However the discovery of the Tianqiaoling flora(located at latitude 43.5°N in NE China) rich in fossils of Dipteridaceae and Cycadophyta, indicating tropic or subtropic conditions, and a comprehensive consideration of assigning the floras of southern Tibet on the basis of palaeomagnetism, plate tectonics, etc., suggest that the palaeophytogeographic regionalization is a rather complicated subject. As the climatic conditions controlling the growth of vegetation changed in three directions one should consider not only the effect of latitudinal change(which usually causes temperature variations from south to north), but also the effect of longitudinal change(which usually brings about variations in humidity from sea to inland) and moreover the effect of vertical or elevation change(which also leads to variations in temperature and humidity). At the same time, it is also necessary to take into consideration the actual palaeogeographic positions of the floras in geologic time.Therefore, it is suggested that the Late Triassic floras in China should be grouped into three floristic regions, namely.(1) the Northern Floristic Region with the Danaeopsis-Symopteris flora,(2) the Southern Floristic Region with the Dictyophyllum-Clathropteris flora, and(3) the Yaflung Zangbo River Floristic Region. It is inferred here that the floral characters of the 3rd region are similar to those of the Dicroidium-Lepidopleris flora growing on Gondwana land at that time.
A new scheme of Late Triassic palaeophytogeographic regionalization of China is put forward on the basis of three principles given as follows: 1. The palaeophytogeographic regionalization should be based on the characters of the various floras themselves. These characters include the types of the dominant floras, compositional patterns of various communities and existence of dominant genera or those genera and species characteristic of a region.2. The palaeogeographic positions of the floras in geologic time should be considered.3. The distribution of the floras was influenced in three directions - latitudinal , longitudinal and vertical - in geological time. Formerly, a number of Chinese palaeobotanists based on the palaeophytogeographic regionalization only on the factor of latitude, and neglected the characters of the floras themselves and the effect of their three-directional zonation. However the discovery of the Tianqiaoling flora (located at latitude 43.5 ° N in NE China) rich in fossils of Dipteridaceae and Cycadophyta, indicating tropic or subtropic conditions, and a comprehensive consideration of assigning the floras of southern Tibet on the basis of palaeomagnetism, plate tectonics, etc., suggest that the palaeophytogeographic regionalization is a rather complicated subject. As the climatic conditions controlling the growth of vegetation changed in three directions one (which usually causes temperature variations from south to north), but also the effect of longitudinal change (which usually knows about variations in humidity from sea to inland ) and moreover the effect of vertical or elevation change (which also leads to variations in temperature and humidity). At the same time, it is also necessary to take into consideration the actual palaeogeographic positions of the floras in geologic time.Therefore, it is suggested that the Late Triassic floras in China should be grouped into three floristic regio ns, name(1) the Northern Floristic Region with the Danaeopsis-Symopteris flora, (2) the Southern Floristic Region with the Dictyophyllum-Clathropteris flora, and (3) the Yaflung Zangbo River Floristic Region. It is inferred here that the floral characters of the 3rd region are similar to those of the Dicroidium-Lepidopleris flora on Gondwana land at that time.