The animal was very similar to the related Thalassomedon, though the structure of the neck vertebrae were different, with taller neural spines and longer supporting processes of the bone, and its nostrils were slightly closer to the tip of the skull. The type specimen of L. morgani contains the best preserved elasmosaurid skull known as well as gastroliths.
The animal was similar to Thalassomedon but had distinct neck vertebrae with taller neural spines and longer supporting processes, along with nostrils closer to the skull's tip. The type specimen of L. morgani has a well-preserved elasmosaurid skull and gastroliths.