arches, small size and the absence of post-cervical osteoderms. In addition, Han et al. (2014) also considered the unfused scapula and coracoid, low and wedge-shaped olecranon process of the ulna, and unfused calcaneum and astragalus of the holotype to be juvenile characteristics. However, Ji et al. (2016) argued that the holotype, and other specimens, instead represented adults due to the lack of fusion of the ribs to the vertebrae, absence of a synsacrum, and small stature of all known specimens. A microanatomical study by Chinese palaeontologist Wenjie Zheng instead concluded that the holotype was no older than 12 months and further suggested that Liaoningosaurus could be the juvenile form of the much larger Chuanqilong. In 2019, Li Xiaobo and Robert R. Reisz investigated three more specimens and also concluded they represented juveniles. Paleoenvironment Yixian Formation Specimens attributable to Liaoningosaurus have been recovered from the Dawangzhangzi and Jianshangou Beds of the Yixian Formation, which is a part of the Jehol Biota. The Yixian Formation is mainly composed of volcanic rocks such as andesites, andesitebreccia, agglomerates and basalts. It represents a freshwater lacustrine environment, lacking rivers and deltas among other variable features of freshwater settings. Such environments lacking these features include shallow lakes. The yearly temperature averaged about 10 °C (50 °F) and was temperate, with distinct wet and dry seasons. The fluctuations in the climate are due to orbital forcing. Conifers related to species that are found in modern subtropical and temperate upland forests dominated the landscape, with ferns, cycads, horsetails, and a small number of flowering plants also being present. Previous dating using 40Ar-39Ar isotopes gave an age of approximately 125 to 120 Ma, although more recent estimates indicate an age of 125.755 ± 0.061 to 124.122 ± 0.048 ma by using U-Pb zircon. The deconstruction and reconstruction of biotic components occurred frequently due to periodic mortality events such as volcanic eruptions, wildfires, and noxious gases erupting from the lakes. Fossils of gastropods, bivalves, ostracods, insects, amphibians, pterosaurs, dinosaurs, birds and mammals have been recovered from the Yixian Formation. Ornithischians from the formation are represented by the hadrosauroids Bolong and Jinzhousaurus; the ceratopsian Psittacosaurus; and the basal neornithischian Jeholosaurus. Saurischians include the sauropods Dongbeititan and Liaoningotitan; the dromaeosaurids Sinornithosaurus and Tianyuraptor; the troodontids Mei and Sinovenator; the therizinosaur Beipiaosaurus; the oviraptorosaurs Caudipteryx and Incisivosaurus; the ornithomimosaurs Hexing and Shenzhousaurus; the compsognathid Sinosauropteryx; and the tyrannosaurs Dilong and Yutyrannus. Jiufotang Formation