Fossil dinosaur embryos are surprisingly rare, being almost entirely restricted to Upper Cretaceous strata that record the late stages of non-avian dinosaur evolution1,2. Notable exceptions are the oldest known embryos from the Early Jurassic South African sauropodomorph Massospondylus3,4 and Late Jurassic embryos of a theropod from Portugal5. The fact that dinosaur embryos are rare and typically enclosed in eggshells limits their availability for tissue and cellular level investigations of development. Consequently, little is known about growth patterns in dinosaur embryos, even though post-hatching ontogeny has been studied in several taxa6. Here we report the discovery of an embryonic dinosaur bone bed from the Lower Jurassic of China, the oldest such occurrence in the fossil record. The embryos are similar in geological age to those of Massospondylus and are also assignable to a sauropodomorph dinosaur, probably Lufengosaurus7. The preservation of numerous disarticulated skeletal elements and eggshells in this monotaxic bone bed, representing different stages of incubation and therefore derived from different nests, provides opportunities for new investigations of dinosaur embryology in a clade noted for gigantism. For example, comparisons among embryonic femora of different sizes and developmental stages reveal a consistently rapid rate of growth throughout development, possibly indicating that short incubation times were characteristic of sauropodomorphs. In addition, asymmetric radial growth of the femoral shaft and rapid expansion of the fourth trochanter suggest that embryonic muscle activation played an important role in the pre-hatching ontogeny of these dinosaurs. This discovery also provides the oldest evidence of in situ preservation of complex organic remains in a terrestrial vertebrate.
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We thank D. Scott for specimen preparation, photography, and figure preparation; N. Campione for morphometric analysis; C. Apaldetti for the data matrix; O. Dülfer for thin sections; G. Grellet-Tinner, M. Sander, J. Steigler, P. Barrett and E. Prondvai for discussion; C. Chu and X. J. Lin for research support; S. P. Modesto and C. Brown for field assistance; J. Liu for assistance in Lufeng; and C. C. Wang, Y. F. Song, Y. C. Lee and H. S. Sheu for help with various experiments at the National Synchrotron Radiation Research Center, Taiwan. Research support was provided by NSERC Discovery and SRO Grants (Canada), University of Toronto, DFG FOR 533 (contribution 130) (Germany), NSC 100-2116-M-008-016 (Taiwan), Ministry of Education (Taiwan) under the NCKU Aim for the Top University Project, Chinese Academy of Sciences and National Natural Science Foundation of China (41150110341).
This file contains Supplementary Information 1-6 , which includes Supplementary Text, a Supplementary Discussion, Supplementary Figures 2.1 -2.5, 3, 4.1 - 4.2, 5.1 - 5.4 and 6.1 - 6.2, 2 Supplementary Tables and additional references.
About this article
Nature Communications (2017)