The discovery of Qianlongshouhu, a new species of dinosaur, reveals that the first dinosaur eggs were likely leathery. This will greatly contribute to our understanding of dinosaur reproductive evolution and the ancestral state of reptile eggshells. (Reconstruction of an ovary containing fossilized embryos.) Credit: NICE Vistudio
Recent research on the newly discovered early Qianlong Shouhu Jurassic Sauropods suggest that early dinosaur eggs had leathery shells. This discovery comes from a comprehensive analysis of dinosaur fossils and shows an important evolutionary change in the morphology of dinosaur eggs. This study also contributes to the understanding of the reproductive characteristics of the ancestors of different reptilian clades.
dinosaur reproductive biology
Over the past 30 years, the discovery of several exceptionally preserved reproductively relevant dinosaur specimens has improved our knowledge of dinosaur reproductive biology. Nevertheless, limited fossil evidence and a lack of quantitative analyzes at broad phylogenetic scales leave many unknowns about dinosaur reproduction, especially before their birth. I was there.Cretaceous period History of evolution.
A breakthrough in egg morphology research
But now, recent fossil discoveries and related analyzes by researchers at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences (CAS) have shown that the first dinosaur eggs were leathery; This suggests that there has been a major change. The egg morphology arose early in the evolution of theropod dinosaurs, not near the origin of birds.
![Skeletal reconstruction of adult and juvenile Qianlong emperors](https://scitechdaily.com/images/Skeletal-Reconstructions-of-Adult-and-Juvenile-Qianlong-777x909.jpg 777w,https://scitechdaily.com/images/Skeletal-Reconstructions-of-Adult-and-Juvenile-Qianlong-342x400.jpg 342w,https://scitechdaily.com/images/Skeletal-Reconstructions-of-Adult-and-Juvenile-Qianlong-768x898.jpg 768w,https://scitechdaily.com/images/Skeletal-Reconstructions-of-Adult-and-Juvenile-Qianlong-1313x1536.jpg 1313w,https://scitechdaily.com/images/Skeletal-Reconstructions-of-Adult-and-Juvenile-Qianlong-1751x2048.jpg 1751w,https://scitechdaily.com/images/Skeletal-Reconstructions-of-Adult-and-Juvenile-Qianlong.jpg 1847w)
Reconstruction of the adult and juvenile Qianlong Emperor skeletons. Credit: IVPP
Discovery of Qianlongshou Lake
This research recently National Science Reviewreports the discovery of a new branching sauropod dinosaur specimen from the Early Jurassic period seed In Guizhou Province, China— Qianlong Shouhu– Consists of three skeletons of adult individuals and clutches of five eggs. This discovery may be the earliest fossil record of an association between adult dinosaurs and nests, and the species name reflects this association. Qianlong means “Dragon of Guizhou”. Ju Hu It means “protection” and refers to the preservation of adult skeletal fossils associated with egg fossils containing embryos.
Qianlong It was a medium-sized basal sauropod dinosaur, weighing 1 ton and measuring about 6 meters long. Embryos show some differences from adults. For example, a proportionally longer skull, a more vertical leading edge of the nose, and fewer teeth.
![Comparison of fossil and extant eggs](https://scitechdaily.com/images/Comparison-of-Fossil-and-Existing-Eggs-777x396.jpg 777w,https://scitechdaily.com/images/Comparison-of-Fossil-and-Existing-Eggs-400x204.jpg 400w,https://scitechdaily.com/images/Comparison-of-Fossil-and-Existing-Eggs-768x391.jpg 768w,https://scitechdaily.com/images/Comparison-of-Fossil-and-Existing-Eggs-1536x783.jpg 1536w,https://scitechdaily.com/images/Comparison-of-Fossil-and-Existing-Eggs-2048x1044.jpg 2048w)
Comparison of fossil eggs (c) with existing soft-shelled, leathery, and hard-shelled eggs. Credit: IVPP
Insights into the behavior and anatomy of the Qianlong Emperor
Allometric analysis of limb ratios between adult and fetal specimens revealed that the adult specimen Qianlong Although able to walk on its hind legs, the baby was probably quadrupedal. General taphonomic and sedimentary features indicate that: Qianlong Like other basal sauropods, it may have used colonial nest building as a reproductive behavior. Massospondylus and Mussaurus.
The researchers also examined the ultrastructure of the eggshell. Qianlong We use multiple techniques including histological thin sectioning, backscattered electron diffraction, energy dispersive spectroscopy, and scanning electron microscopy.The results showed that Qianlong The eggshell microstructure is similar to other Cretaceous dinosaur egg fossils, and it probably had a fully developed eggshell unit, consisting of two layers: a papillary layer and a continuous layer. The calcareous layer is Qianlong The eggs were much thicker than most soft shell eggs, but thinner than hard shell eggs.A comparison of eggshell fragmentation between different eggshell types shows that the surface of the eggshell is Qianlong It featured small fragments resembling a leathery eggshell, in contrast to the folded surface of soft-shelled eggs and the large fragmented surface of hard-shelled eggs.These observations indicate that Qianlong She laid leathery eggs.
![Summary of ancestral eggshell types of major nodes](https://scitechdaily.com/images/Summary-of-Ancestral-Eggshell-Type-for-Major-Nodes-762x1024.jpg 762w,https://scitechdaily.com/images/Summary-of-Ancestral-Eggshell-Type-for-Major-Nodes-298x400.jpg 298w,https://scitechdaily.com/images/Summary-of-Ancestral-Eggshell-Type-for-Major-Nodes-768x1032.jpg 768w,https://scitechdaily.com/images/Summary-of-Ancestral-Eggshell-Type-for-Major-Nodes-1143x1536.jpg 1143w,https://scitechdaily.com/images/Summary-of-Ancestral-Eggshell-Type-for-Major-Nodes-1525x2048.jpg 1525w,https://scitechdaily.com/images/Summary-of-Ancestral-Eggshell-Type-for-Major-Nodes.jpg 1608w)
Summary of ancestral eggshell types of major nodes with maximum posterior probabilities in all ASR analyses. Credit: IVPP
Evolutionary trends of dinosaur eggs
To test macroevolutionary patterns of selected reproductive traits throughout the transition from dinosaurs to birds, researchers collected data from 210 fossil and extant species representing all major reptilian clades. , we tested evolutionary trends using multiple time scale phylogenies.
They found that relative egg size decreased from the base of Dipoda to the base of Saurischia, but showed an increasing trend from early theropods to the crown-avian section. The most significant increase in egg size occurred early in theropod evolution. Regarding eggshell thickness, they found that thickness tended to decrease from the base of archosaurs to the base of saurischians, and then eggshell thickness increased significantly early in theropod evolution. did. A trend toward increased eggshell thickness was also observed in the evolution of sauropods.
Egg shape was generally conserved in the evolution from diapsids to modern birds. For example, theropod egg elongation peaked in oviraptorosaurs, which had the largest egg elongation of any diapsid, but later returned to its ancestral state. As a result, only slightly elongated eggs were inherited by all crested bird clades.
Overall, reconstructing the ancestral conditions of different types of eggshells supports the conclusion that the first dinosaur eggs were probably leathery, relatively small, and oval. Additionally, leathery eggshells were probably an ancestral state in Avemetatarsaria, the archosaur, and Testudines.
Reference: “Exceptional Early Jurassic fossil with leathery eggs sheds light on dinosaur reproductive biology” Fenglu Han, Yilun Yu, Shukang Zhang, Rong Zeng, Xinjin Wang, Huiyang Cai, Tianzhuang Wu, Written by Yingfeng Wen, Sifu Cai, Chun Li, Rui Wu, Qi Zhao and Xing Xu, October 9, 2023. National Science Review.
DOI: 10.1093/nsr/nwad258