Mixosaurus was a small ichthyosaur, measuring  long and weighing . The largest specimens would have measured over  in length. It possessed a long tail with a low fin, suggesting it could have been a slow swimmer, but also possessed a dorsal fin for stability in the water.
Mixosaurus was a compact ichthyosaur, measuring  long and weighing . The largest specimens would have measured over  in length. It had a lengthy tail with a low fin, indicating it may have been a slow-moving swimmer, but also featured a dorsal fin for balance in the water.