#leninia

Leninia was a genus of opthalmosaurine ichthyosaur from the Early Cretaceous. Its type species is L. stellans. Its only fossil was found in the bank of the Volga river in Russia. Leninia has the third largest sclerotic ring of any known ichthyosaur, only beat by Baptanodon and Temnodontosaurus.

Leninia is indirectly named after Russian leader Vladmir Lenin, as the museum its fossil is housed in is within the Lenin Memorial and Lenin school complex in Ulyanovsk; as such, the name reflects the fossil's geohistorical location. The species name stellans refers to the fossil's star-shaped frontal-parietal suture.

Its autapomorphies include the presence of an anterior process on the prefrontal over the nasal, a frontal-parietal suture caused by forked processes on both bones, the posterior process of the maxilla extending up to the middle orbit, and the presence of a process on the supratemporal that contacts the parietal.

The only known fossil is a partial skull. It consists of the area from the back of the skull up to the naris, ending in a clean break. Leninia, while being one of the latest-living opthalmosaurines, was recovered as one of the most basal. The presence of a large sclerotic ring and apterure indicates that both are ancestral characteristics of opthalmosaurines, not derived. This also suggests that, unlike Opthalmosaurinae's sister taxon Platypterygiinae, opthalmosaurines did not diversify outside of a "deep diver" niche.

Original paper: Found here