''Aigialosaurus'' is an extinct genus of Late Cretaceous marine or semiaquatic lizard classified as part of the family Aigialosauridae within the Mosasauroidea. Exclusively found in deposits of Cenomanian age near Hvar (city), Hvar, Croatia, the genus contains one valid species, ''A. dalmaticus''.Madzia, D., Cau, A. (2017)
Inferring "weak spots" in phylogenetic trees: application to mosasauroid nomenclature
PeerJ 5:e3782 According to recent molecular and morphological data, ''Aigialosaurus'' is the oldest known member of the lineage leading to large Cretaceous marine reptiles called mosasaurs, a group most closely related to snakes among living squamates.Grigoriev, D. V. (2013). "Redescription of ''Prognathodon lutugini'' (Squamata, Mosasauridae)." ''Proceedings of the Zoological Institute RAS'', 317(3): 246-261. It was a relatively small reptil with a complete specimen measuring long. Another primitive mosasauroid, ''Opetiosaurus'', was suggested to represent a second species of ''Aigialosaurus'' in 2009, "''Aigialosaurus bucchichi''",Dutchak, Alex R.; and Caldwell, Michael W. (2009
"A redescription of ''Aigialosaurus'' (= ''Opetiosaurus'') ''bucchichi'' (Kornhuber, 1901) (Squamata: Aigialosauridae) with comments on mosasauroid systematics".
''Journal of Vertebrate Paleontology'' 29 (2): 437-452. though this conclusion has not been supported by recent analyses.

References

Mosasaurs Mosasaurs of Europe Fossil taxa described in 1892 Taxa named by Dragutin Gorjanović-Kramberger {{Cretaceous-reptile-stub