Morphometric Study of The Ediacaran Tubular Fossils Sinotubulites

Sinotubulites is a kind of late Neoproterozoic straight or slightly curved cylindrical tubular fossils with multiple sets of wall structure and both ends open. It has now been found worldwide, and regarded as one of the representatives of the tubular animal radiation before the Cambrian explosion. In this paper, morphological data about Sinotubulites in the Ediacaran Gaojiashan Biota at the Lijiagou section of Ningqiang, Shaanxi province were analyzed to explore the possible relationship between the characteristics of each part of Sinotubulites in ontogenetic process. A total of 378 well preserved fossil samples were selected for measurement, among which 150 apertural and 134 side view samples were examined under scanning electron microscopy (SEM), and 94 samples were examined under micro-scope, of them, the latter was only used as supplementary data for more accuracy analysis. Through the data processing, it was found that a positive linear relationship exists between the maximum diameter and the diameter of the inner circle (Linear regression R²=0.7), and the linear relationship between the maximum diameter (both five radiant and six radiant tubes) and unilateral length is the most robust (Linear regression, R²=0.8903) in Sinotubulites tubes. In general, there is no significant correlation between the tube length and the wall thickness, either bet ween the tube length and the maximum diameter. The results showed that Sinotubulites may simply discarded its old tube, and secreted a new one to construct a home at different stages of the growth. At the same time, under turbulent hydrodynamic conditions, Sinotubulites, may rely on the variable longitudinal ridges to stabilize the tubes, instead of the secretion of thicker shell walls.