Mussentuchit member fossil eggshell light microscope photographs and corresponding metrics

The first fossil eggshell from the Cenomanian-age Mussentuchit Member of the Cedar Mountain Formation was described over fifty years ago. In the half-century since, oodiversity of this rock unit has been limited to a single, taxonomically unstable ootaxon, currently formulated as Macroelongatoolithus carlylei. Recently, there has been a renewed effort to recover and describe the macrofauna of the Mussentuchit; however, these advances are limited to the body fossil record. Here, we examine the range of eggshells present in the Mussentuchit Member and assess the preserved biodiversity they represent. Gross morphological and microstructural inspection reveals a greater diversity of eggshells than previously described. We identify six ootaxa: three Elongatoolithidae oogenera (Macroelongatoolithus, Undulatoolithus, Continuoolithus), eggs laid by oviraptorosaur dinosaurs; two oospecies of Spheroolithus laid by ornithopod dinosaurs; and Mycomorphoolithus kohringi, laid by a crocodylomorph. The..., In this study, we examined all fossilized eggshells recovered from the Mussentuchit Member of the Cedar Mountain Formation and housed at the NCSM (n > 2,500), plus additional loaned material from the OMNH (n > 1,500), FMNH (n = 77), and BYU (n = 8), to extensively analyze ootaxonomic diversity across twenty localities.  NCSM and FMNH fragments from the Mussentuchit Member were collected between 2012 and 2022, and fragments and thin section slides loaned from BYU and the OMNH were collected by Jensen and Cifelli et al., respectively.
We systematically categorized fragments of eggshell into ‘morphotypes’ based on external ornamentation patterns, and selected the highest quality samples (free of additional matrix, appropriately sized) for photography and consumptive sampling. Fragments selected were photographed with a Keyence VHX-7000 Digital Microscope before creating radial thin sections to assess microstructural features such as crystal arrangement, pore networks, the ML/CL bound..., , # Mussentuchit member fossil eggshell light microscope photographs and corresponding metrics

[https://doi.org/10.5061/dryad.51c59zwjb](https://doi.org/10.5061/dryad.51c59zwjb)

## Description of the data and file structure

These data were collected as part of a study to assess the diversity of the eggshell assemblage of the Cenomanian-age Mussentuchit Member of the Cedar Mountain Formation in Emery County, Utah.

### Files and variables

#### File: Mussentuchit\_Egg\_Cross\_Sections.zip

**Description:** Images of the eggshells used in this study in radial cross section under both plane- and cross-polarized light

#### File: Mussentuchit\_Egg\_Fragments\_Photographs.zip

**Description:** Images of the fragments used in this study. There are images of both the surfaces of the eggs and then in cross section at two magnifications.

#### File: Mussentuchit\_Eggshell\_Thin\_Section\_Matrix.csv

**Description:** Final matrix assembled to assess quantitative and qualitative values for the e...