Searching for a Clue to Characterize a Crystalline Dinosaur’s Eggshell of Baja California, Mexico

Abstract

This work presents a detailed structural and morphological analysis of different dinosaur eggshells such as Spheroolithus (sample 1, 2), lambeosaurinae, Prismatoolithus , and one unidentified ootaxon performed by high-resolution scanning electron microscopy (HRSEM). These ancient eggshells of Late Cretaceous dinosaurs were collected in the coastal area of El Rosario, Baja California in Mexico. Additionally, a thorough study was performed on the elements present in the samples by different techniques such as energy-dispersive spectroscopy (EDS), X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS). The XPS technique was performed to make an accurate identification of the compounds of two different types of eggshells ( Spheroolithus sample 1 and Prismatoolithus ). This contribution compares the surface of five different dinosaur eggshells of 74 Ma and their inner section to determine the morphology, distribution of the chemical elements present, as well as their relationship. The observed morphology of the ornithopod eggshells of the herbivorous species shows that the mammillary cones are in the form of columns with microaggregates and irregular pores. In contrast, in the theropod eggshells, the mammillary cones are observed in different forms with wider pores. Finally, the chemical components present in the structures of each of the samples were estimated using the information obtained from SEM-EDS, evidencing the presence of calcite, quartz, and albite in each of the samples. The composition reveals that eggshells contain Si, P, S, K, Ca, Mn, Fe, and Sr and trace elements such as Cr, Cu, and Zn. The presence of heavy metals may be an indication that the eggshells presented diagenetic alterations.

Molecular Analysis of the Mineral Phase and Examination of Possible Intramineral Proteins of Dinosaur Eggshells Collected in El Rosario, Baja California, Mexico

“…The emission lines found correspond mainly to calcite, albite, and quartz, which were also observed in previous studies. 18 As it was almost impossible to identify other peaks appearing at low emission intensities, the fluorescence of the eggshell of current species such as the ostrich, emu, and crocodile had been developed (see the Supporting Information), to clarify if these wavelengths corresponded to calcium, since it was known by SEM-EDS that the eggshells of the current species were composed only of calcium carbonate (Figure S4).…”

Fractal Analysis of the Distribution and Morphology of Pores in Dinosaur Eggshells Collected in Mexico: Implications to Understand the Biomineralization of Calcium Carbonate

“…Some samples of eggshells belong to ornithopod (herbivores) and theropod (carnivores) dinosaurs of the Hadrosauridae and Troodontidae families, respectively. Those of the Hadrosauridae family correspond to the oogenus Spheroolithus , and the oogenus Prismatoolithus correspond to the Troodontidae family . The prefixes “oo” (egg) and “ oolithus ” (stone egg) are added to differentiate oospecies, oogenus, and oofamilies of dinosaurs. , …”

“…Among these records is the collection of eggshells in the town of El Rosario, Baja California, corresponding to the Late Cretaceous (74 MY). 26 The prefixes "oo" (egg) and "oolithus" (stone egg) are added to differentiate oospecies, oogenus, and oofamilies of dinosaurs. 27,28 We analyzed two eggshells of the oogenus Spheroolithus (samples 1 (I) and 2 (III)); one of the family Lambeosaurinae (II), which is part of the Hadrosauridae family, with the oogenus nonidentified; one of the oogenus Prismatoolithus (IV); and one nonidentified ootaxon (V).…”

“…These ancient eggshells of Late Cretaceous dinosaurs were collected in the coastal area of El Rosario, Baja California in Mexico. 26 These eggshells of different species of dinosaurs were first washed with 5% ethylenediaminetetraacetic acid (EDTA) with the aim of eliminating the organic membrane and then they were washed with Milli-Q water and air-dried. All samples were observed with an SZH10 OLYMPUS microscope on both sides to determine the corresponding sides of the eggshells.…”