''Aigialosaurus'' is an extinct genus of

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

marine or semiaquatic lizard classified as part of the family

Aigialosauridae Aigialosauridae (from Greek, ''aigialos'' = "seashore" and ''sauros''= lizard) is a family of Late Cretaceous semiaquatic pythonomorph lizards closely related to the mosasaurs. Regarded by some paleontologists as a distinct monophyletic group ...

within the Mosasauroidea. Exclusively found in deposits of Cenomanian age near

Hvar Hvar (; Chakavian: ''Hvor'' or ''For'', el, Φάρος, Pharos, la, Pharia, it, Lesina) is a Croatian island in the Adriatic Sea, located off the Dalmatian coast, lying between the islands of Brač, Vis and Korčula. Approximately long, wi ...

Croatia , image_flag = Flag of Croatia.svg , image_coat = Coat of arms of Croatia.svg , anthem = "Lijepa naša domovino"("Our Beautiful Homeland") , image_map = , map_caption = , capit ...

, 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

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on ...

s, a group most closely related to

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...

s among living

squamate Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, it ...

s.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 ''Opetiosaurus'' 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, Croatia , image_flag ...

'', 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