The holotype (MTM 2011.43.1) and referred specimens have been collected from the alluvial sediments of the Csehbánya Formation from various exposures at the Iharkút open-pit bauxite mine, Bakony Hills, Western Hungary since the discovery of the locality in 2000.

[2] Since then, more than one hundred bones of Pannoniasaurus, sourced from a large number of individuals of differing age classes, are known from the alluvial flood-plain deposits that comprise the Csehbánya Formation.

Since all remains are isolated bones, the basis for the referral of this material to Pannoniasaurus is based on similar methods used by other authors, such as Houssaye et al. in their study of Pachyvaranus crassispondylus in 2011.

[2] Though all remains (including the holotype) of Pannoniasaurus are isolated bones, the density of the specimens, the various size classes, the large number of similar elements from individual animals, and their unique characters, make it possible to link them together into a single taxon.

A number of isolated teeth were attributed to Pannoniasaurus that are similar to Halisaurus, being conical and curved posterolingually, bear crowns with fine anastomosing longitudinal striae, and have a strong mesial but weaker labiodistal carina.

[2] A single vertebra of Pannoniasaurus (MTM V.2000.21), as well as a variety of fish and crocodile teeth, were collected from the waste dump of the subterranean Ajka coal mine.

[2] The discovery of Pannoniasaurus indicates that, similar to some lineages of cetaceans, mosasauroids quickly radiated into a variety of aquatic environments, with some groups reinvading available niches in freshwater habitats, and becoming highly specialized within those ecosystems.