DOI: 10.5061/dryad.6djh9w1cd
title: Data from: Biogenic origin of secondary eggshell units in dinosaur eggshells elucidates lost biomineralization process in maniraptoran dinosaurs

description: Although rarely seen in modern avian eggshells, secondary eggshell units
 are remarkable structures in non-avian dinosaur eggshells and provide
 paleobiological information. However, the origin of secondary eggshell
 units has rarely been studied, which has resulted in controversies in
 paleontology because abiogenic origin has also been suggested for the
 formation of secondary eggshell units. Here, we show that secondary
 eggshell units of non-avian dinosaur eggshells are biogenic structures
 using a combination of microscopic techniques, mainly electron backscatter
 diffraction (EBSD) and scanning electron microscope (SEM). The features of
 secondary eggshell units suggest that the formation mechanism of
 non-maniraptoran dinosaur eggshells is comparable to that of turtle and
 crocodile eggshells. Matrix fibers appear to be the initiators of
 secondary eggshell units. A weakening trend of secondary eggshell units
 toward non-avian maniraptoran dinosaurs supports that maniraptoran
 dinosaurs evolved a more organized physiological mechanism of eggshell
 formation.
description: The thin sections are prepared following the usual thin section
 preparation methods of geological studies and the images were obtained
 using a polarized light microscope. EBSD analysis of
 fossil eggshells followed an established protocol (see Choi et al. 2023,
 Journal of Vertebrate Paleontology). 
description: # Data from: Biogenic origin of secondary eggshell units in dinosaur
 eggshells elucidates lost biomineralization process in maniraptoran
 dinosaurs Dataset DOI: [10.5061/dryad.6djh9w1cd](10.5061/dryad.6djh9w1cd)
 ## Description of the data and file structure --- General Information Data
 from: "Biogenic origin of secondary eggshell units in dinosaur
 eggshells elucidates lost biomineralization process in maniraptoran
 dinosaurs" Please contact Seung Choi
 ([seung0521@gmail.com](mailto:seung0521@gmail.com);
 [seung0521@snu.ac.kr](mailto:seung0521@snu.ac.kr)) for information. The
 data were collected during 2019-2025. Data and File Overview This
 submission contains PLM images (JPEG files), and EBSD files in.ctf format
 which can be viewed with an open source, such as ATEX EBSD software
 ([http://www.atex-software.eu/)](http://www.atex-software.eu/\))) and .cpr
 and .crc format which is available at Channel 5. The JPEG files in the
 EBSD file folders show the representative EBSD images (Inverse Pole Figure
 Y maps) that can be acquired from the respective EBSD files, so the users
 can check whether the EBSD files correspond to the ones that we authors
 have uploaded. For following ootaxa and modern turtle (*Astrochelys
 radiata*) and crocodile (*Caiman crocodilus*) eggs, both PLM images and
 EBSD files are available: *Placoolithus tumiaolingensis*: 19-1, 1-7, and
 3-22, all of which belong to the egg clutch TML 4. Dictyoolithid eggshell:
 8889(g) (ZMNH M8889). *Faveoloolithus ningxiaensis*: F5-1(IVPP V4709).
 *Youngoolithus xiaguanensis*: Y1-1, Y3-1, and Y3-2, all of which belong to
 the egg clutch IVPP V5783. Stalicoolithid eggshells: 8102, 8929-a, and
 8929-b (ZMNH M8102 and M8929). *Megaloolithus siruguei*: p2 and p4 (IVPP
 V31358). *Paraspheroolithus irenensis*: 731 (IVPP V731).
 *Multifissoolithus megadermus*: 2337 (IVPP V2337). *Stromatoolithus
 pinglingensis*: cgd75 (IVPP V33471) For *Testudoolithus zelenitskyae* (MOR
 710), only EBSD files are available. The PLM images contain the regions of
 interest photographed under both transmitted and polarized lights. The
 secondary eggshell units are marked by white and black arrows. Some of
 them are selected to perform EBSD analysis. Because secondary eggshell
 units can be observed more easily on IPF maps, the secondary eggshell
 units with typical crystallographic characteristics but not shown in the
 PLM images are also selected for EBSD analysis.  Some of the EBSD files
 correspond to the figures in the main text and supplementary figures, but
 some files are not shown as figures in the text. With these files, one can
 reconstruct the diverse types of EBSD mappings, including inverse pole
 figures (IPF), grain boundary (GB), and Euler mappings. Code/Software ATEX
 EBSD software
 ([http://www.atex-software.eu/](http://www.atex-software.eu/)). The
 version 3.3.0 is able to open the EBSD files that we uploaded. One can
 click 1. Import data-&gt;2. Select data-&gt;3. Select “.ctf” files that we
 uploaded-&gt;4. Click “Create ATEX file”-&gt; Then one can see the
 reconstructed EBSD images.