Some Small Two-valve Shell. Chengjiang Biota Arthropods

As we all know, Bilateral symmetry, three-layer embryo, metamerism and having a relatively developed head are the common characteristics of the Arthropoda and Annelida, So it is believed that arthropod originated from annelid. But as a matter of fact, Athropoda has some more complex characteristics than Annelida, such as the exoskeleton, departmental body-plan and segmented appendages, which, as one parameter, results in the abundance of arthropod fossils in the Chengjiang Fossil Lagerstatte.During the primary research work of Chengjiang biota, the Paleontologists had an idea that the bivalved arthropod Kunmingella douvilleiyas the dominant species because they found that eighty percent of the fossils they excavated in Chengjiang Fossil Lagerstatte were Kunmingella douvillei. And they also found that Naraoia longicaudata, Naraoia spinosa and Isoxys auritus which belong to Arthropoda were the sub-dominant species. Heliomedusa orienta and Maotianshania cylindrical were also two different sub-dominant species. The former is a kind of brachiopod and the latter belongs to Vermes. The fossils of each sub-dominant species took its place from three percent to five percent in quantity.On one hand, the fossils of early Vertebrata, Hemichordata, Urochordata, Cephalochordata and Vetulicolian which connects Invertebrata and Vertebrata have been caught one by one in the continuous excavating work of Early Life Institute field work team of North West University since 1996. And all of these fossils provide us with a best Window into the "Cambrian Explosion" . On the other hand, because of the big quantity of the arthropod fossils, Arthropoda is still the phylum which is researched most frequently and deeply.The order Nebalia belongs to Arthropoda. There are about 20 kinds of living nebalia, and the fossils of Nebalia are being excavated. The Chuandianella, one genus in Nebalia, has been published. In this dissertation except for Chuandianella ovata being described in more detail, several new species and a species whose name is not determinedare described based on studying the collected specimens, All of these species belong to one family: Chuandianidae.This dissertation is composed of five main aspects:1. The geological setting of Chengjiang biotaFirstly, the pattern of Chinese tectonic has been cited, which can help us to understand the place of China in the world clearly and easily. Secondly, The Lower Cambrian of China and the early cambrian geomorph of eastern YunNan have been included. And the paleogeomorph of Chengjiang Fossil Lagerstatte is refered as well.2. The distribution of Chengjiang biotaIn this part some new localities in Wuding, Anning, Yiliang, Haikou, and so on, which are discovered by ELI field work team, are showed. Two sections are described particularly, from which most of the fossils to be described in this dissertation are excavated.3. The traditional classification of fossils and some essential entombment theory throwing light on the forming process of the soft-bodied fossils.4. The study situation of genus Chuandianella.5. The suggestion to establish the new genus and the description of type species.