High-resolution CT-scan data reveals the tooth replacement pattern of the Late Jurassic tyrannosauroid Guanlong wucaii (Dinosauria, Theropoda)

摘要: The Tyrannosauridae, which is characterized by specialized pachydont dentition and putative bone-cracking predatory strategies, is one of the most extensively studied theropod lineages. Although tooth replacement patterns, crucial for understanding feeding behaviors, have been thoroughly studied in this group, studies on non-tyrannosaurid tyrannosauroids are relatively scarce. This study utilizes high-resolution CT data to investigate the tooth replacement pattern in two specimens of Guanlong wucaii, a Late Jurassic tyrannosauroid, and provides insights into the evolution of tooth replacement across Tyrannosauroidea. Second-generation replacement teeth, a rarity observed mainly in giant predatory theropods (e.g. some tyrannosaurids), were detected in the dentary dentition of the juvenile Guanlong. Zahnreihen reconstructions display a consistent cephalad alternating tooth replacement pattern in the maxilla and the dentary of both of the examined individuals, with Z-spacing values exceeding 2.0. As Guanlong grows, the Z-spacing value in the maxillary dentition increases, resembling the ontogenetic changes documented in the Tyrannosauridae. Additionally, like Tarbosaurus, Guanlong also displays a discontinuity between the tooth replacement waves at the premaxilla-maxilla boundary. This study thus demonstrates that some tyrannosaurid-like tooth replacement patterns were acquired before the origin of the Tyrannosauridae.