Abstract:
Microstructures of the siphonal and cameral deposits in a well preserved Telychian nautiloid Eridites undulatum collected from Guizhou are studied through thin sections under a polarization microscope and etched,polished sections under a scanning electron microscope.Organic sheets and layers of mineral crystals,whose form and thickness are stable,are found in the siphonal deposits.Two layers overlap alternatively with growth of the siphonal deposits.Organic sheets and layers of mineral crystals of the cameral deposits are irregular in form and thickness,prismatic crystals can be seen in the layers of mineral crystals.Based on the microstructural characteristics,it has been suggested that the siphonal deposits may have been precipitated directly by the epithelial cells of the soft body,and the cameral deposits could have been produced by body fluids which penetrated into the connecting rings and resulted in the formation of an organic membrane that made the organic sheets and crystal layers deposit successively in the camerae.Furthermore,through the comparison with the microstructural features of the siphonal and cameral deposits of Carboniferous pseudorthocerids,the microstructural characteristics of pseudorthoceroids may not be used as a valid taxonomical criterion.
