New information on multispherulitic dinosaur eggs: Faveoloolithidae and Dendroolithidae

ABSTRACT

Dinosaurs produced a broad range of different types of eggs. Some of which have no analogue among those laid by living reptiles and birds. Eggs with shell units branching into an unusual labyrinth associated with a complicated pneumatic system were assigned to the parataxonomic oofamilies Faveoloolithidae and Dendroolithidae. While numerous new related ootaxa were described recently, many biological aspects as well as the identity of their producers have remained unknown or unresolved. Here, we provide the first experimental evidence that some mid-sized dendroolithid eggs were laid by a therizinosauroid theropod. We scanned and studied two faveoloolithid eggs. One of them contains putative embryonic remains that correspond to an articulated cranial skeleton exhibiting rather reduced antorbital region/opening similar to that in titanosaurian embryos. Another faveoloolithid egg exhibits unusual bending of the uninterrupted shell; we discuss three alternative interpretations: natural deformation, pathology and pliability, to explain this unusual phenomenon.

KEYWORDS:

• Dinosauria
• reproduction
• egg
• eggshell flexibility
• pathology
• Faveoloolithidae
• Dendroolithidae

Acknowledgements

We thank Michael J. Benton (University of Bristol, School of Earth Sciences, Bristol, UK) and Hans-Dieter Sues (National Museum of Natural History, Smithsonian Institution, Washington, USA) for their valuable comments and improvements to the manuscript; Anna Ďurišová (Curator of Vertebrate Paleontology, The Slovak National Museum – Natural History Museum); Terry W. Manning (Freelance Paleo Technician, Cortaro, USA); and Jin Xingsheng (Curator of Vertebrate Paleontology, Zhejiang Museum of Natural History, Hangzhou, China) for allowing the access of the specimens for this study. M.K. thanks Karol Sabath for earlier consultation and assistance with the first microstructural analysis; Konstantin Mikhailov for providing literature and consultations; Zhao Zi-kui and Zhao Hong for providing less accessible Chinese papers and information on a dinosaur ichnospecimen associated with the faveoloolithid nest. We thank Vladimír Ferko (Department of Radio-diagnostics, Hospital & Health Centre, Michalovce, Slovakia) and Martin Noskovič (Siemens, Bratislava, Slovakia) for the serial coronal CT scanning of the Mongolian egg specimens. M.K. thank to Kentaro Uesugi and Masato Hoshino (Spring-8, Hyogo, Japan) for project cooperation that produced the synchrotron scan of the Chinese egg specimen. We thank Jozef Lauruský for making photographs used in Figure 1(a-d). Finally, we would like to thank the anonymous reviewer whose comments were constructively critical and profesisonally helpful to improve the final version of our study.

Disclosure statement

The authors declare no competing interests.

Author contributions

M.K. and A.R.I.C. conceived the project; M.K. wrote the manuscript with input from A.R.I.C.; M.K. conducted the specimen sampling, SEM, examination of the physical thin sections and photographed the specimens; M.K. and A.R.I.C. prepared the figures; both authors interpreted the data, M.K. edited the final version of the manuscript.

Additional information

Funding

This study was supported by the Slovak Research and Development Agency (APVV-18-0251), the Japan Synchrotron Radiation Research Institute (grant 2017A-1714), the International Research Program – Sepkoski Grants 1999, all grants awarded to M.K..