Abstract: Choristoderes was a group of diapsid reptiles that appeared in the Middle Jurassic and became extinct in the Miocene. In the Early Cretaceous (~140 Ma), a lineage of Choristoderes, called the Neochoristoderes, evolved a gharial-like body plan. Neochoristoderes inhabited shallow water of rivers and lakes; the adults grow to longer than 1 m, with a long snout and sharp teeth for catching fish. Fossil juvenile Neochoristoderes are rarely discovered; therefore, it remains unclear how this lineage developed the specialized long snout through ontogeny. Recently, the smallest individual of Neochoristoderes, Mengshanosaurus minimus,has been reported from the Lower Cretaceous Mengyin Formation of Shandong Province. The holotype is an almost complete fossil skull with a total length of 35 mm, representing a juvenile. This specimen shows the morphology of the Neochoristoderan skull at an early ontogenetic stage. This paper provides a high-resolution X-ray computed tomography (HRCT) dataset of the Mengshanosaurus minimus holotype, including the original CT data with a spatial resolution of 7.5197 μm. The three-dimensional CT model of the Mengshanosaurus minimus skull revealed detailed osteological information for comparative studies with other Neochoristoderes regarding their morphology, systematics, and ontogenetic process. The dataset includes a three-dimensional surface polygon mesh of the Mengshanosaurus minimus skull. This surface model can be optimized for 3D print and used for academic research, education, and scientific outreach.
Keywords: Mengshanosaurus minimus; juvenile; HRCT scan; three-dimensional reconstruction