[1] The holotype material consists of only the posterior of trunk and the tail, discovered in France, in Gigondas.

[1] However, identifying metriorhynchid genera from post-cranials is not easy,[2] as such until diagnostic material is discovered Neustosaurus is considered nomen dubium.

[3] Neustosaurus has been considered a junior synonym of either Dakosaurus [3] and Geosaurus [4] over the past 100 years.

In 2009, Young and Andrade published a re-description of Geosaurus, examining its relationships and the validity of species lumped into the genus.

They concluded that Neustosaurus is a nomen dubium, but if new material was discovered it would be the senior synonym of Cricosaurus.