Simoliophis rochebrunei is a snake restricted to the Cenomanian of southwestern Europe. It is the type species of the genus Simoliophis, the latter being the type genus of the Simoliophiidae, i.e. the family that is comprised of the marine hindlimbed snakes. The first descriptions of the species were insufficient and dealt only with mid-trunk vertebrae, whereas vertebrae from other parts of the vertebral column are markedly different from the latter. Paradoxically, species subsequently included in the genus are better known than the type species. In the present article, S. rochebrunei is described and diagnosed on the basis of material found recently in the type area (Charentes, southwestern France). Strong pachyostosis affects the mid-trunk and the anterior portion of the posterior trunk region. A part of the vertebral column affected by pachyostosis was more or less stiff. As with all pachyostotic squamates, S. rochebrunei was aquatic; it lived in shallow marine water, whose bottom was sandy, but it was also able to enter brackish environments. It was a slow swimmer capable of shallow, but long dives. The species may be used as a stratigraphic marker since it is restricted to the lower Cenomanian in the type area.