Genus
Valid Extinct

Halisaurus

Marsh 1869

Halisaurus is an extinct genus of mosasaur named by Othniel Charles Marsh in 1869. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination of features and prompted a new genus to be described. Its name is a portmanteau of the Ancient Greek ἅλς and σαῦρος. It was renamed by Marsh to Baptosaurus in 1870, since he believed the name to already be preoccupied by the fish Halosaurus. According to modern rules, a difference of a letter is enough and the substitute name is unneeded, making "Baptosaurus" a junior synonym.

Temporal range
Triassic
Jurassic
Cretaceous
Paleogene
Neogene
252 201 145 66 0 Ma
⚠ The temporal range slightly exceeds the K-Pg boundary (66 Ma). Likely an interval offset in PBDB data.
PBDB occurrences
30
Group
Mosasaures
Carnivore aquatic Terrestrial
Halisaurus
click to enlarge
Halisaurus mosasaur, Wyoming Dinosaur Center, Thermopolis / 2006 © Greg Goebel from Loveland CO, USA · CC BY-SA 2.0 · Wikimedia
PBDB ↗ Wikipedia ↗
Classification
Mosasauridae Family
›
Halisaurinae Unranked clade
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Halisaurini Unranked clade
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Halisaurus Genus
Fossil sites 30 geolocated sites
Distribution
Top countries
🇺🇸 United States
14
🇲🇦 Morocco
7
🇨🇱 Chile
2
🇵🇪 Peru
1
🇯🇴 Jordan
1
🇦🇴 Angola
1
🇨🇩 DR Congo
1
🇪🇬 Egypt
1
🇳🇪 Niger
1
🇦🇷 Argentina
1
Geological formations
Navesink
3
Severn
3
Blufftown
1
Vivian
1
Mount Laurel
1
Merchantville
1
Marshalltown
1
Tar Heel
1
Phosphorite Unit
1
Mocuio
1
Temporal distribution
Maastrichtian (72.2–66 Ma)
23
Campanian (83.6–72.2 Ma)
7
Species (4)
Halisaurus arambourgi 72 Ma
Halisaurus hebae 72 Ma
Halisaurus onchognathus
Halisaurus platyspondylus 84 Ma
Synonyms (1)
Baptosaurus nomen dubium Halisaurus
Images 6
Bibliography
Original description
J. J., Jr. Sepkoski. 2002. A compendium of fossil marine animal genera. Bulletins of American Paleontology 363:1-560
Bibliography (22)
R. A. Otero. 2025. Review of two marine vertebrate assemblages from the Arauco Basin (central Chile) reveals diversity changes throughout the Maastrichtian. Cretaceous Research 166(78):105996 DOI ↗
T. Rempert, B. Martens, and A. Vinkeles Melchers. 2024. Mosasaurs (Squamata: Mosasauridae) from the Late Cretaceous (Late Maastrichtian) of North Carolina, USA. Proceedings of the Zoological Institute RAS 328(3):384-391 DOI ↗
A. A. Shaker, N. R. Longrich, and A. Strougo, A. Asan, N. Bardet, M. K. Mousa, A. A. Tantawy, G. A. Abu El-Kheir. 2023. A new species of Halisaurus (Mosasauridae: Halisaurinae) from the lower Maastrichtian (Upper Cretaceous) of the Western Desert, Egypt. Cretaceous Research 154:105719 DOI ↗
P. Jiménez-Huidobro, R. A. Otero, and S. Soto-Acuña, M. W. Caldwell. 2019. Reassessment of cf. Plotosaurus from the upper Maastrichtian of Chile, with comments on the South American distribution of halisaurine mosasaurs. Cretaceous Research 103:104162:1-9 DOI ↗
M. S. Fernández and M. Talevi. 2015. An halisaurine (Squamata: Mosasauridae) from the Late Cretaceous of Patagonia, with a preserved tympanic disc: Insights into the mosasaur middle ear. Comptes Rendus Palevol 14:483-493 DOI ↗
H. Cappetta, N. Bardet, and X. Pereda Suberbiola, S. Adnet, D. Akkrim, M. Amalik, A. Benabdallah. 2014. Marine vertebrate faunas from the Maastrichtian phosphates of Benguérir (Ganntour Basin, Morocco): Biostratigraphy, palaeobiogeography and palaeoecology. Palaeogeography, Palaeoclimatology, Palaeoecology 409:217-238 DOI ↗
O. Mateus, M. J. Polcyn, and L. L. Jacobs, R. Arujo, A. S. Schulp, J. Marinheiro, B. Pereira, D. P. Vineyard. 2012. Cretaceous amniotes from Angola: dinosaurs, pterosaurs, mosasaurs, plesiosaurs, turtles. Actas de V Jornadas Internacionales sobre Paleontologia de Dinosaurios y su Entorno, Salas de los Infantes, Burgos
M. J. Polcyn, J. Lindgren, and N. Bardet, D. Cornelissen, L. Verding, A. S. Schulp. 2012. Description of new specimens of Halisaurus arambourgi Bardet & Pereda Suberbiola, 2005 and the relationships of Halisaurinae. Bulletin de la Société Géologique de France 183(2):123-136 DOI ↗
J. Lindgren. 2007. First record of Halisaurus (Squamata: Mosasauridae) from the Pacific coast of North America. PaleoBios 27(2):40-47
N. Bardet, X. Pereda Suberbiola, and M. Iarochene, B. Bouya, M. Amaghaz. 2005. A new species of Halisaurus from the Late Cretaceous phosphates of Morocco, and the phylogenetical relationships of the Halisaurinae (Squamata: Mosasauridae). Zoological Journal of the Linnean Society 143:447-472 DOI ↗
N. Bardet and X. Pereda Suberbiola. 2002. Marine reptiles from the Late Cretaceous Phosphates of Jordan: palaeobiogeographical implications. Geodiversitas 24(4):831-839
W. B. Gallagher. 2002. Faunal changes across the Cretaceous-Tertiary (K-T) boundary in the Atlantic coastal plain of New Jersey: restructuring the marine community after the K-T mass-extinction event. Catastrophic Events and Mass Extinctions: Impacts and beyond. GSA Special Paper 356:291-301 DOI ↗
R. B. Holmes and H.-D. Sues. 2000. A partial skeleton of the basal mosasaur Halisaurus platyspondylus from the Severn Formation (Upper Cretaceous: Maastrichtian) of Maryland. Journal of Paleontology 74(2):309-316 DOI ↗
M. W. Caldwell and G. L. Bell, Jr. 1995. Halisaurus sp. (Mosasauridae) from the Upper Cretaceous (Santonian) of east-central Peru, and the taxonomic utility of mosasaur cervical vertebrae. Journal of Vertebrate Paleontology 15(3):532-544 DOI ↗
T. Lingham-Soliar. 1994. First record of mosasaurs from the Maastrichtian (Upper Cretaceous) of Zaire. Palaeontologische Zeitschrift 68(1/2):259-265 DOI ↗
W. B. Gallagher. 1993. The Cretaceous/Tertiary mass extinction event in the North Atlantic coastal plain. The Mosasaur 5:75-154
B. S. Grandstaff, D. C. Parris, and R. K. Denton, Jr, W. B. Gallagher. 1992. Alphadon (Marsupialia) and Multituberculata (Allotheria) in the Cretaceous of eastern North America. Journal of Vertebrate Paleontology 12(2):217-222 DOI ↗
T. Lingham-Soliar. 1991. Mosasaurs from the Upper Cretacous of Niger. Palaeontology 34(3):653-670
A. J. Robb. 1989. The Upper Cretaceous (Campanian, Black Creek Formation) fossil fish fauna of Phoebus Landing, Bladen County, North Carolina. The Mosasaur 4:75-92
D. Baird. 1986. Upper Cretaceous reptiles from the Severn Formation of Maryland. The Mosasaur 3:63-85
D. R. Schwimmer. 1986. Late Cretaceous fossils from the Blufftown Formation (Campanian) in western Georgia. The Mosasaur 3:109-123
D. Baird and G. R. Case. 1966. Rare marine reptiles from the Cretaceous of New Jersey. Journal of Paleontology 40(5):1211-1215