Thalassomedon

Thalassomedon (from Greek, thalassa, "sea" and Greek, medon, "lord" or "ruler", meaning "sea lord") is a genus of plesiosaur, named by Welles in 1943.

==Description== upright|thumb|left|Restoration thumb|Detail of Thalassomedon skull at the American Museum of Natural History Thalassomedon is among the largest elasmosaurids, with the holotype measuring long and weighing more than . There is a larger skull, however, suggesting a much larger animal, potentially up to . The neck is also very long; it comprises 62 vertebrae and is about - over half of the total length. The skull is long, with long teeth. The flippers were about long. Stones have been found in its stomach area leading some to theorize that they were used for ballast or digestion. If the latter, stomach action would cause the stones to help grind ingested food.