Thalattosaurs are one of the three major groups of top reptilian predators in the Triassic marine ecosystems, the study of which is a key to our understanding of biotic recovery from the Permo-Triassic mass extinction. Significant advancement has been achieved in the last decades in studying biodiversity and phylogeny of Thalattosaurs. However, the origin of Thalatto-saurs and the process forming the biogeographical pattern of Thalattosaurs largely remains an enigma. We review here the recent progress in the study of Thalattosaurs in terms of its origin, species diversity, phylogeny and biogeography. Our re-view shows that large gap exists in the research of Thalattosaurs. Future research should be focused on field work in the early part of the Triassic strata to search for more primitive Thalattosaurs. This is necessary to elucidate its origin. A first-hand systematic review of Thalattosaurs from SW China should be performed to clarify the true biodiversity of Thalat-tosaurs, which is also a basis for a comprehensive phylogenetic analysis of thalattosaurian relationships. Finally, the study of the physiology and paleoecology of Thalattosaurs via the investigation of long bone histology and microanatomy is of great significance in establishing the process forming the biogeographical pattern of Thalattosaurs.
