Recently, a research team from the Dinosaur Evolution Research Center and the Geological Museum, College of Earth Sciences, Jilin University, published findings on the relative growth rates of Changchunsaurus parvus, a basal ornithopod dinosaur. Through paleohistological analysis of fossil bones, the research team discovered that Changchunsaurus parvus possessed an extremely slow growth rate and delayed sexual maturity. This finding reveals the adaptive evolution of relative growth rates in such small-bodied dinosaurs under conditions of limited resources and environmental constraints. The results provide critical scientific evidence for an in-depth understanding of the survival strategies of basal ornithopods, their co-evolutionary mechanisms with the environment, and the evolution of terrestrial vertebrate ecosystems across the transition between the Early and Late Cretaceous.
Figure: Reconstructed model and fossil skeleton of Changchunsaurus parvus
Changchunsaurus parvus was unearthed from the Upper Cretaceous Quantou Formation in central Jilin Province, on the southern margin of the Songliao Basin. This basal ornithopod was excavated, studied and named by researchers from Jilin University in the early 2000s. It represents a key taxon of early Neornithischia and constitutes the core member of the Changchunsaurus Fauna (Chen et al., 2025). As one of the most successful dinosaur clades, Neornithischia spread across all continents globally during the Cretaceous. Ontogenetic research based on bone histology of members of this clade has been widely conducted (e.g., Cerda & Chinsamy, 2012; Han et al., 2020; Zhao et al., 2019). Nevertheless, precisely determining the timing of full skeletal maturity and maximum body size remains challenging, and knowledge of the ontogeny of small species within this group is particularly limited (Erickson & Tumanova, 2000; Zhao et al., 2019). Featuring a combination of plesiomorphic and derived ornithopod traits, Changchunsaurus parvus occupies a basal phylogenetic position along the ornithopod lineage, making it an ideal model for investigating the ontogeny of early neornithischians.
Figure: A – Skeletal reconstruction of Changchunsaurus parvus; B – Schematic diagram of femora selected for ontogenetic analysis and sampling positions for thin sections
In this study, the team adopted histological techniques to observe and analyze femur fossils from seven Changchunsaurus parvus individuals of varying body sizes. Using proxies including skeletal growth marks, vascular density and bone tissue types, the researchers systematically reconstructed the full growth sequence of Changchunsaurus parvus, spanning juvenile, subadult and adult life stages. The results indicate that:
Changchunsaurus parvus exhibited a markedly slower growth rate than most known dinosaurs, with a mass-independent growth rate of merely 1.87×10⁻³ g¹ᐟ⁴/day—among the lowest values ever documented for dinosaurs worldwide. Sexual maturity was reached at approximately 7–8 years of age, later than other small basal neornithischians. Full somatic maturity took around 14 years, and adult individuals weighed roughly 6.2 kg, classifying this species as a small dinosaur characterized by slow growth and delayed maturation.
Figure: Growth curve of Changchunsaurus parvus
Abbreviations: SM = Sexual Maturity; AM = Asymptotic Mass
Compared with its sister taxon Jeholosaurus, Changchunsaurus parvus attained a substantially smaller adult body size. Fossil comparisons show that the fibula of the holotype adult specimen of Changchunsaurus parvus measures 138 mm in length, while a subadult Jeholosaurus fibula already reaches 148 mm, exceeding the adult fibula length of Changchunsaurus parvus. Even when accounting for allometric growth effects (i.e., the non-fixed proportional relationship between long bone dimensions and body mass), the adult body size of Jeholosaurus is confirmed to be significantly larger than that of Changchunsaurus parvus.
Figure: Histological micrograph of a subadult Changchunsaurus parvus femur
Abbreviations: PB = Parallel-Fibered Bone; FB = Fibrolamellar Bone; MC = Medullary Cavity
Integrating sedimentary and paleoclimatic evidence from the Quantou Formation of the Songliao Basin, the team further infers that the early Late Cretaceous Songliao Basin experienced a generally hot, semi-arid climate. Resource scarcity and environmental pressure likely contributed to the evolutionary development of a slow-growth life strategy in Changchunsaurus parvus.
The above research was formally published on May 29, 2026, in the internationally renowned paleontology journal Palaeogeography, Palaeoclimatology, Palaeoecology (abbreviated as PPP). The paper bears the title Exceptionally slow growth rates and life history of Changchunsaurus parvus from the Upper Cretaceous Quantou Formation, Songliao Basin, Northeast China. Wang Longhan, a PhD candidate from the College of Earth Sciences, Jilin University, serves as the first author. Research Librarian Chen Jun of the Dinosaur Evolution Research Center and Geological Museum is the corresponding author. PhD candidate Tea Maho and Master’s student Jordan Young from the University of Toronto, alongside Distinguished Foreign Professor Academician Robert Reisz of Jilin University, participated in project research and manuscript preparation.
This research was supported by the National Repository of Rock, Mineral and Fossil Specimens, the National Key R&D Program of China, the National Natural Science Foundation of China, the Joint International Research Laboratory of Future Science at Jilin University, the State Key Laboratory of Deep Earth Exploration and Imaging, and the Bioarchaeology Laboratory. Notably, the work also received funding from the China International Talent Exchange Foundation’s China Exchange Program for Young International Talents (CEP). The two graduate students in paleontology from the University of Toronto were invited to Jilin University in the summer of 2025. Under the joint supervision of Chinese and foreign supervisors, they engaged in academic seminars, field surveys, professional training and collaborative laboratory experiments alongside Chinese graduate students. This scientific cooperation and cultural exchange fostered academic friendships among young paleontologists and facilitated the production of joint research outputs.
Article Links
https://doi.org/10.1016/j.palaeo.2026.113931
https://www.sciencedirect.com/science/article/pii/S0031018226003949?via%3Dihub
References
Chen, J., Mao, F., Wu, W., Meng J., 2025. New Material of the Zalambdalestid Zhangolestes (Mammalia, Zalambdalestidae) from the Late Cretaceous Changchunsaurus Fauna of Jilin, China. Acta Geologica Sinica 99, 634–645.
Han, F., Zhao, Q., Stiegler, J., Xu, X., 2020. Bone histology of the non-iguanodontian ornithopod Jeholosaurus shangyuanensis and its implications for dinosaur skeletochronology and development. Journal of Vertebrate Paleontology 40, e1768538.
Cerda, I.A., Chinsamy, A., 2012. Biological implications of the bone microstructure of the Late Cretaceous ornithopod dinosaur Gasparinisaura cincosaltensis. Journal of Vertebrate Paleontology 32, 355–368.
Zhao, Q., Benton, M.J., Hayashi, S., Xu, X., 2019. Ontogenetic stages of ceratopsian dinosaur Psittacosaurus in bone histology. Acta Palaeontologica Polonica 64, 323–334.
Erickson, G.M., Tumanova, T.A., 2000. Growth curve of Psittacosaurus mongoliensis Osborn (Ceratopsia: Psittacosauridae) inferred from long bone histology. Zoological Journal of the Linnean Society 130, 551–566.
