广西百色第三纪哺乳动物群与气候变迁

在广西百色共发现了三个层位:晚始新世早期的洞均组,晚始新世晚期的那读组和早渐新世的公康组。它们的哺乳动物的种类数目分别为14,27和ll,而其南方类型的百分含量则分别为50,77.8和54.5。故在晚始新世早期或早渐新世,气候较凉;而在晚始新世晚期,气候较暖。这是与北美的情况相类似的。

PALEOGENE CLIMATE CHANGE AND MAMMALIAN FAUNA IN BOSE BASIN OF GUANGXI

There are three successive mammalian faunas in Bose Basin of Guangxi. Table 2 shows the correlation of mammalian faunas in Eastern Asia. Table 2. Fischer and Arthur (1977) held that warm periods largely correspond to the polytaxic ones, while colder episodes coincide with states of oligotaxy or biotic crisis. Fig. 1 indicates the specific diversity of the above three mammalian faunas. Therefore the climate was cool in the early stage of Late Eocene (Dongjun Fauna), warm in the late stage of Late Eocene (Nadu Fauna), and cold in the Early Oligocene (Gongkang Fauna). The following forms are present in Dongjun Fauna. Carnivora Eudinoceras crassum Felidae Perissodaetyla ?. Eusmilus sp. Brontotheriidae Condylartbra cf.Protitan sp. Mesonychidae Metatelmatherium sp. Andrewsarchus crassum Deperetellidae Pantodonta Diplolophodon cf. similis Coryphodontidae Teleolophus sp. Amynodontidae Prohyracodon sp. cf. Gigantamynodon sp. ? Ilianodon sp. Amynodon sp. Artiodactyla cf. Paramynodon sp. Anthracotheriidae Rhinocerotoidea ? Probrachyodus sp. Forstercooperia sp. The six genera (Andrewsarchus, Eudinoceras, Protitan, Metatelmatherium, Teleolophus and Forstercooperia) have beenfound in Irdin Manha Fauna of Inner Mongolia, and Eusmilus found in Lushi Fauna of Henan. So in the early stage of Late Eocene there are seven genera (50%) found both in southern and in northern parts of Eastern Asia. There are four genera (Paramynodon, Prohyracodon, Ilianodon and Probrachyodus) present only in southern parts (i.e. Bose Basin of Guangxi and Lunan Basin of Yunnan). Therefore the percent of typical southern elements is 28.6% in Dongjun Fauna. Gigantamynodon, Amynodon and Diplolophodon have been found in northern parts too, but the former two in Shara Murun Fauna of Inner Mongolia and the last one in Hoti Fauna of Shanxi. So there is no evidence to demonstrate that in the early stage of Late Eocene these genera once lived in northern parts. It is probable that'during the late stage of Late Eocene they migrated from southern parts to northern ones of Eastern Asia. Therefore the percent of southern elements is 50% in Dongjun Fauna (Fig. 2). Listed below are the known mammals of Nadu Fauna. Creodont Hyraeodontidae Hyaenodontidae Gaenolophus sp. ? Propterodon sp. Artiodactyla Carnivora Anthracotheriidae Canidae Anthracothema rubricae ? Pachycynodon sp. Anthracokeryx birmanicus Urasidae Anthracokeryx moriturus Cephalogale sp. Anthracokeryx cf. bambasae cf. Cephalogale sp. Heothema chengbiensis Condylarthra Heothema media Mesonyehidae Heothema angusticalxia Guilestes acares Bothriodon tientongensis cf. Harpagolestes sp. Bothriodon Chyelingensis Phenacodontidae Tayassuidae Eodesmatodon spanios gen. 1 indet. Perissodactyla gen. 11 indet. Eomoropidae Hypertragulidae Eomoropus cf. quadridentatus Indomeryx cotteri Amynodontidae Indomeryx youjiangensis Paramynodon sp. Indomeryx sp. Huananodon hui Notomeryx baisensis Guixia simplex Propterodon has been found in Irdin Manha Fauna of Inner Mongolia, Harpagolestes, Caenolophus in Shara Murun Fauna of Inner Mongolia, Eomoropus in Hoti Fauna of Shanxi, Bothriodon in Late Eocene Fauna of Xinjiang. Therefore in the late stage of Late Eocene there are five genera (six species) (i.e. 22.2%) found both in southern and in northern parts of Eastern Asia. As discussed above, Paramynodon found only in southern parts. Anthracothema, Anthracokeryx, Indomeryx are also present in Pondaung Fauna of Burma. Many species, such as Anthracothema rubricae, Anthracokeryx birmanicus, Anthracokeryx moriturus, Anthracokeryx bambasae, Indomeryx cotteri, have been found both in Guangxi and in Burma. Besides, Guilestes, Eodesmatodon, Huananodon, Guixia and Notomeryx are endemic animals in Guangxi. Therefore the percent of typical southern elements is 59.2% in Nadu Fauna. Pachycynodon, Cephalogale and the two genera of Tayassuidae are present in many places of Eurasia, but they are all found in the Oligocene. So there is no evidence to indicate that in the late stage of Late Eocene they once lived in northern parts. Perhaps, they spread over the vast areas during the Oligocene. Therefore the percent of southern elements is 77.8% in Nadu Fauna (Fig. 2). As mentioned above, the number of species of Dongjun and Nadu Faunas is 14 and 27 respectively. The percent of southern elements is 50% and 77.8% in Dongjun and Nadu Faunas separately. Besides, Nadu Fauna of Guangxi and Pondaung Fauna of Burma are very similar. Both of them have many species of Anthracotheriidae. All these facts indicate that the climate in the late stage of Late Eocene was much warmer than that in the early stage of Late Eocene. The number of species in Gongkang Fauna is lesser than in Dongjun and Nadu Faunas. A list of its mammals is given below. Carnivora Artiodactyla Machairodontinae Anthracotheriidac ? Hoplophoneus sp. Huananothema imparilica gen. indet. Heothema bellia Perissodaetyla Anthracokeryx gungkangensis. Amynodontidae Anthracokeryx kwangsiensis Guixia youjiangensis Bothriodon tientongensis Huananodon hyypodonta Tayassnidae Chalicotheriidae gen. indet. Schizotherium nabanensis Schizotherium has also been found in Oligocene Fauna of Inner Mongolia, Bothriodon and the genera of Machairodontinae and Tayassuidae are present in many places of Eurasia and also in North America. So in Early Oligocene there are five genera (i.e. 45.5%) found both in southern and northern parts of Eastern Asia. All the others, such as Guixia, Huananodon, Huananothema, Heothema and Anthracokeryx ate the specialized forms survived from the time of Nadu Fauna. The percent of southern elements is 54.5% in Gongkang Fauna. Obviously, they are much lesser than those of Nadu Fauna. The number of species of Gongkang Fauna is much lesser than that of Nadu Fauna too. These facts indicate that the climate in Early Oligocene was much colder than that in the late stage of Late Eocene. Fig. 3 was given by Wolfe (1978). It shows that in North America the climate in the late stage of Late Eocene was warmer than that in the early stage of Late Eocene, as in the case of Guangxi. During the Early Oligocene, just as Wolfe (1980) said, "The climate deterioration at the terminus of the Eocene resulted in a major shift. Not only did mean annual temperature radically decline, there was a major shift to low equability." Therefore the climatic changes in North America and those in Eastern Asia are very similar.