摘要
对于哺乳类来说,始新世中、晚期是一个很重要的“更新”时期。许多古老的哺乳动物明显地衰退,甚至绝灭,同时,更为进步的种类的出现,却为现代动物群的形成奠定了基础。对于这一哺乳动物发展的重要时期的研究,在我国起步较晚,但也有近百年的历史。 1892年,俄国著名的地质学家V.A.Obruchev在内蒙古采到一块雷兽的牙齿碎片(见Osborn,1930),这也许是我国中、晚始新世哺乳类化石第一次有纪录的发现。在本世纪的二、三十年代,国外学者在我国进行大规模的调查研究,奠定我国中。
The Middle and Late Eocene mammalian fossil localities are widespread in 28 basins in China. This paper gives a review on the main localities. Although certain mammalian families have been studied, no Summary of the total assemblages is available until recently. The Middle and Late Eocene mammalian faunas in China are most adequately represented by those derived from Nei Mongol. Since the first tooth fragment of brontothere waa found by V. A. Obruchev in 1892, a number of mammalian fossils have been collected from the Irdin Manha, Camp Margetts, and Shara Murun areas. The fossilbearing deposits and the mammalian faunas of these areas have been used as the basis for subdividing the Middle and Late Eocene into the Arshatan, Irdinmanhan, and Sharamurunian ages. The Arshatan age was not clear until Qi (1987) described the Arshato mammalian fauna. In the Camp Margetts area (Hubebolhe) the yellow and grey sandstones originally labeled 'Houldin' have been proved to be equivalent to the Irdin Manha beds in age, and the red and grey clays, labeled 'Irdin Manha' to the Arshato beds, Therefore, Gobiatherium mirificum, Advenimus burkei, etc. should be considered to come from the Arshato beds, and Hypercoryphodon themsoni to be an element of the Irdinmanhan faunas. Some important localities scatter in several intermontane basins of the Qinliing Mountains. The Wangjiapo (Mengchiapo) local fauna and the Hetaoyuan local fauna are good representatives for the Irdinmanhan faunas, in Central China. In the Lushi and Liguanqiao basins, there have been found the Arshatan and Sharamurunian mammalian fossils (Xu et al., 1979; Tong and Wang, 1980, 1981), with a major Sharamurunian fossil locality situated near the Rencun Village in the Yuanqu Basin, from where about 21 taxa were recorded. Overlying the deposits containing typical Sharamurunian mammals in this basin are the dark clays alternating with grey marls, which are called the Zhaili Member of the Heti Formation (Zdansky's, Loc. 1). From the grey clays there have been collected some primitive cricetids and zapodids associated with abundant anthracotheres. A Middle Eocene fauna comparable to the Arshato fauna of Nei Mongol has been found in the middle part of the Guanzhuang Formation near the Xizhou Village, west of the Xintai County in Shandong. The fossilbearing deposits may be younger in age than those around the Guanzhuang Village, NW of the Mengyin County. The mammalian taxa from Xizhou are listed in Table 1. Paleontologically, the Lunan and Bose Basins are important in South China. In the Lunan Basin, the taxa from the upper and lower parts of the Lumeiyi Formation are roughly comparable with the Sharamurunian and Irdinmanhan mammals of North and Central China respectively. In the Bose Basin, the Dongjun Formation is here considered to be Sharamurunian in age based on the presence of Diplolophodon, Gigantamynodon, Paramynodon, llianodon, and Probrachyodus. Overying the Dongjun Formation is the Naduo Formation from which more abundant artiodactyls have been recorded than perissodactyls either in taxa or in specimens. It is characterized by the abnndance of anthraeotheres and primitive hornless ruminants, and the absence of index fossils for the Early Oligocene Ulangochuian faunas, such as Embalotherium, Cadurcodn, Entelodon, Miomeryx, Lophiameryx, etc. The Naduo fauna might represent an assemblage of the interval between the Sharamurunian and Ulangochuian ages; the living time of this fauna is named the Naduan age in this paper. The faunas listed in Table 1 exhibit the, scantiness of smaller mammals, followed by the larger mammals which provide the main evidence available for our discussion on the characters of the mammalian faunas. The Arshatan faunas are dominated by perissodactyls with helaletid tapiroids as main elements; while archaic ungulates, uintatheres, coryphodonts, and mesonychid condylarths are frequently present. In these faunas Uintatherium. Mesonyx, Thinocyon, Helaletes, Hyrachyus., and Telmatherium are also known from the Bridgerian deposits of North America. In the Irdinmanhan age, the mammalian faunas are mainly dominated by perissodactyls in composition, with a lower percentage of archaic ungulates. Among the perissodactyls, endemic lophialetid and deperetellid tapiroids, which first appeared in the Arshatan age, are flourishing in contrast with the decline of helaletids. Eomoropids and anmynodonts are the first recorded mammals from the Irdinmanhan deposits, although they might have appeared earlier. Remainsof coryphodonts are usually found, but rather rare, and so far uintatheres have not been collected from the Irdinmanhan deposits. Mesonychid condylarths are various in Nei Mongol, but scant in other areas. The most common carnivorous animals are Propterodon (Creodonta) and Miacis (Carnivora). In particular, the presence of Eomoropus, Forsterco operia, Triplopus?, and Harpagoletes? in the Irdinmanhan faunas can be taken as an evidence for correlation with the early Uintan faunas in North America. In the Sharamurunian faunas, perissodactyls still play a major role; rhinoceratids are quite numerous and diverse although tapiroids tend to reduce, especially lophialetids. Amynodonts and hyracodonts are widespread and progressively spe- cialzed, and the primitive rhinoceratids, Prohyracodon and llainodon, have been found in Central and South China In that time, artiodactyts became an important part; Dichobune-like and Gobiohyuslike artiodactyls still remained; ruminants made their first appearance in Asia, and anthracotheres were greatly diversified; coryphodonts and mesonychid condylarths were surviving and their distributions were only restrioted within central and South China, Pterodon and Hyaenodon are the most common carnivorous mammals, which also appeared in North America, until the Duchenan age. The aspect of the Naduan faunas has not been perfectly understood up to now, however, available material shows that they are distinguishable from the Sharamurunian faunas in composition. Their most significant features are the ascendancy of artiodaetyls and the descendancy of perissdactyls. The diversified and flourishing anthracotheres and primitive ruminants make up the main parts oftheir composition, In addition, primitive tayassuids have been first recorded in the Nadu Formation. The reduction of perissodactyls is distinct, with only several amynodonts and rhihoceratids ever reported. There is no sharp break between these Middle and Late Eocene mammalian faunas, but changes in faunal composition are prominent. The extinction or decline of archaic ungulates and the re duction of perissodactyls are almost simultaneous with the rise of artiodactyls. An tnorease in the endemic genera from Arshatan age to Naduan age suggests relatively regional isolation. Nevertheless, it is also true that some lineages, rising in Central Asia immigrated into other continents at the end of Eocene or later, for example, lagomorphs, cricetids, zapodids, tayassuids, etc. The discoveries of largea anthracothere, Anthracothema, in Japan and in Timor, Indonesia perhaps indicate the lower sea level sometime in the Naduan age, or later, which was beneficial to the emigration: from the Asiatic mainland to remote oceanic islands for non-volant land-mammals.
出处
《古生物学报》
CAS
CSCD
北大核心
1989年第5期663-682,共20页
Acta Palaeontologica Sinica
