Sauropod teeth from the Khorat Group of Thailand suggest the faunal turnover of sauropod dinosaurs across the J/K boundary

Sauropod teeth are among the most abundant vertebrate fossils recovered from the Upper Jurassic to Lower Cretaceous Khorat Group of Thailand. However, their taxonomic and palaeoecological significance has not previously been examined in detail. This research presents the first comprehensive taxonomic identification of isolated sauropod teeth from several localities across the Khorat Plateau in Northeastern and Eastern Thailand. Based on morphological analyses, these teeth were assigned to three distinct morphotypes. Additionally, multi-quantitative analyses revealed affinities with three sauropod clades: Mamenchisauridae, Titanosauriformes, and Diplodocoidea. The taxonomic framework recovered in this study is consistent with the broader sauropod fossil record of the Khorat Group and reveals a marked faunal shift across the Jurassic–Cretaceous boundary of Thailand. Mamenchisaurids appeared during the Late Jurassic to the earliest Cretaceous, whereas neosauropods, such as titanosauriforms and diplodocoids, became more prevalent during the Early Cretaceous. This turnover pattern matches the evolutionary trends reported from East Asia. These findings provide new evidence for a major sauropod faunal replacement event, likely driven by ecological changes affecting herbivorous dinosaurs during this crucial timeframe of the Mesozoic.