2026/07/15 by Lu-Yan Qi, Yi-Wei Hu, Qiang Li +2 · 1 voice
Earth and Planetary Sciences · Environmental Science · Agricultural and Biological Sciences · #Paleontology and Evolutionary Biology #Ichthyology and Marine Biology #Fossil Insects in Amber
paper · pdf · doi:10.3897/fr.29.195364
openalex publication_date 2026/07/15 · openalex created_date 2026/07/16 · openalex updated_date 2026/07/20
Thalattosaurs were a group of large predators in the Triassic oceans, and their diversity is therefore crucial for understanding the biotic recovery from the end-Permian mass extinction in marine environments. Specimen HFUT GL-17-006, a very small thalattosaur skeleton from the Late Triassic Guanling Biota, was recently suggested to represent a new thalattosauroid species sharing no affinity with Xinpusaurus , one of the most common marine reptiles in that biota. Here, we re-examined the morphology of HFUT GL-17-006 and conducted new bone histological analyses. The results indicate that the specimen is a rapidly growing juvenile individual, as evidenced by its small body size, unfused neural arches and centra, and immature bone tissue. Reassessment of the ontogenetically and taphonomically sensitive characteristics of HFUT GL-17-006 recovered it within a clade containing Xinpusaurus suni in our new phylogenetic analysis. Specifically, HFUT GL-17-006 shares with X. suni the absence of a frontal-supratemporal contact and the presence of a reniform radius, both of which distinguish it from other currently recognized species of Xinpusaurus . Thus, HFUT GL-17-006 is identified as a juvenile individual of X. suni , rather than a new thalattosauroid species as recently proposed. Together, our results highlight the importance of rigorously assessing ontogeny before erecting new species or interpreting phylogenetic relationships.