Occitanosaurus was described by Sciau et al. (1990) and Bardet et al. (1999). The genus name was erected for ‘Plesiosaurus’ tournemirensis by Bardet et al. (1999). The taxon was originally regarded as an early elasmosaurid but is now considered a member of Microcleididae. Occitanosaurus was approximately 3.9 meters long.
The type material: MMM J. T. 86-100, Musée Municipal de Millau, Aveyron, as a nearly complete skeleton including the skull, complete vertebral series with atlas-axis and associated ribs to the sacrum, complete pectoral and pelvic girdles, right forelimb and both hind limbs.