Fractal analysis of the distribution and morphology of pores in dinosaur eggshells collected in Mexico: implications to understand the biomineralization of calcium carbonate

Abstract

In this work, we present an investigation of the surface area and roughness of different dinosaur eggshells of 70 million years old using fractal dimension analysis obtained from atomic force microscopy (AFM) and scanning electron microscopy (SEM) information. We also conduct qualitative analyses on the external and inner surfaces of eggshells, which are mainly composed of calcium carbonate. The morphological characteristics of both surfaces can be revealed by both SEM and AFM techniques. It is observed that the inner surface of the eggshell has greater roughness that increases the surface area due to the vaster number of pores compared to the external face, making, therefore, the fractal dimension also greater. The aim of this contribution is to identify the morphology of the pores, as well as the external and inner surfaces of the eggshells, since the morphology is very similar on both surfaces and will otherwise be difficult to determine with the naked eye by SEM and AFM. In addition, the sole AFM analysis is very complicated for these types of samples due to the intrinsic roughness. However, it needs additional methods or strategies to complete this purpose. This contribution used the fractal dimension to show the same behavior obtained in both SEM and AFM techniques, indicating the fractal nature of the structures.