Megacephalosaurus is an extinct genus of brachauchenine pliosaurid plesiosaur known from the early Late Cretaceous Carlile Shale (middle Turonian stage) of Russell County, Kansas, United States. It contains a single species, Megacephalosaurus eulerti.
Species taxanomy provided by GBIF Secretariat (2022). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on 2023-06-13; License: CC BY 4.0