Editing Mosasaur

{{short description|Extinct marine lizards of the Late Cretaceous}}
{{distinguish|text=[[mesosaur]]s, marine reptiles of the Permian}}
{{Automatic taxobox
| name = Mosasaurs
| taxon = Mosasauridae
| authority = [[Paul Gervais|Gervais]], 1853
| fossil_range = [[Late Cretaceous]], {{Fossil range|94|66|earliest=98}}<ref name=PolcynSarabosaurus>{{Cite journal |author1=Polcyn, M.J. |author2=Bardet, N.|author3=Albright III, L.B. |author4=Titus, A.|year=2023 |title=A new lower Turonian mosasaurid from the Western Interior Seaway and the antiquity of the unique basicranial circulation pattern in Plioplatecarpinae |journal=[[Cretaceous Research]] |volume=151 |doi=10.1016/j.cretres.2023.105621 |doi-access=free |bibcode=2023CrRes.15105621P }}</ref>
| image = Platecarpus planifrons Clean.png
| image_upright = 1.2
| image_caption = Mounted skeleton of a [[Russellosaurina|russellosaurine]] (''[[Plesioplatecarpus planifrons]]'')
| subdivision_ranks = Subgroups
| subdivision =
*{{extinct}}[[Halisaurinae]]
*{{extinct}}[[Mosasaurinae]]
*{{extinct}}'''Russellosaurina'''
**{{extinct}}[[Plioplatecarpinae]]
**{{extinct}}[[Tethysaurinae]]
**{{extinct}}[[Tylosaurinae]]
**{{extinct}}[[Yaguarasaurinae]]
}}

'''Mosasaurs''' (from [[Latin]] ''Mosa'' meaning the '[[Meuse]]', and [[Ancient Greek|Greek]] {{lang|grc|σαύρος}} ''{{lang|grc-Latn|sauros}}'' meaning 'lizard') are an extinct group of large aquatic reptiles within the family '''Mosasauridae''' that lived during the Late Cretaceous. Their first [[fossil]] remains were discovered in a limestone quarry at [[Maastricht]] on the Meuse in 1764. They belong to the order [[Squamata]], which includes [[lizard]]s and [[snake]]s.

During the last 20 million years of the Cretaceous period ([[Turonian]]–[[Maastrichtian]] ages), with the extinction of the [[ichthyosaur]]s and [[Pliosauridae|pliosaurs]], mosasaurids became the dominant marine predators. They themselves became extinct as a result of the [[Cretaceous–Paleogene extinction event|K-Pg event]] at the end of the Cretaceous period, about 66 million years ago.

==Description==
[[File:Platecarpus tympaniticus.jpg|thumb|250px|left|Life restoration of a mosasaur (''[[Platecarpus tympaniticus]]'') informed by [[Trace fossil|fossil skin impressions]]]]
Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, shallow [[Inland sea (geology)|inland seas]] prevalent during the Late [[Cretaceous]] period. Mosasaurs were so well adapted to this environment that they most likely [[Viviparity|gave birth to live young]], rather than returning to the shore to lay eggs as [[sea turtle]]s do.<ref>{{cite journal
|title= Pelagic neonatal fossils support viviparity and precocial life history of Cretaceous mosasaurs
|first1= Daniel J.
|last1= Field
|first2= Aaron
|last2= LeBlanc
|first3= Adrienne
|last3= Gau1
|first4= Adam D.
|last4= Behlke
|journal= Palaeontology
|date= 10 April 2015
|doi= 10.1111/pala.12165
|volume=58
|issue = 3
|pages=401–407
|s2cid= 4660322
|doi-access= free
|bibcode= 2015Palgy..58..401F
}}</ref>

The smallest-known mosasaur was ''[[Dallasaurus|Dallasaurus turneri]]'', which was less than {{convert|1|m|ft|abbr=on}} long. Larger mosasaurs were more typical, with many species growing longer than {{convert|4|m|ft|abbr=on}}. ''[[Mosasaurus|Mosasaurus hoffmannii]]'', the largest known species reached up to {{convert|17|m|ft|abbr=on}},<ref>{{Cite journal| last = Grigoriev| first = D.W. | title = Giant Mosasaurus hoffmanni (Squamata, Mosasauridae) from the Late Cretaceous (Maastrichtian) of Penza, Russia | journal = Proceedings of the Zoological Institute RAS | volume = 318 | issue = 2| pages = 148–167| year = 2014 | doi = 10.31610/trudyzin/2014.318.2.148 | s2cid = 53574339 | url = https://www.zin.ru/journals/trudyzin/doc/vol_318_2/TZ_318_2_Grigoriev.pdf | access-date = 26 June 2016}}</ref> but it has been considered to be probably overestimated by Cleary ''et al.'' (2018).<ref name=Clearyetal>{{cite journal|author1=Terri J. Cleary|author2=Roger B. J. Benson|author3=Susan E. Evans|author4=Paul M. Barrett|title=Lepidosaurian diversity in the Mesozoic–Palaeogene: the potential roles of sampling biases and environmental drivers|year=2018|journal=Royal Society Open Science|volume=5|issue=3 |pages=171830|doi=10.1098/rsos.171830|pmid=29657788 |pmc=5882712 |bibcode=2018RSOS....571830C |doi-access=free}}</ref> Currently, the largest publicly exhibited mosasaur skeleton in the world is on display at the [[Canadian Fossil Discovery Centre]] in [[Morden, Manitoba|Morden]], [[Manitoba]]. The specimen, nicknamed "Bruce", is just over {{convert|15|m|ft|abbr=on}} long,<ref>{{cite web|url= http://www.guinnessworldrecords.com/world-records/118041-largest-mosasaur-on-display |title= Largest mosasaur on display |work= Guinness World Records |year=2014 |access-date=27 June 2016}}</ref> but this might be an overestimate as the skeleton was assembled for display prior to a 2010 reassessment of the species that found its original number of vertebrae to be exaggerated, implying that the actual size of the animal was likely smaller.<ref name=BruceNewsletter>{{cite news |author=CBC News |date=August 27, 2008 |title=Manitoba dig uncovers 80-million-year-old sea creature |url=https://www.cbc.ca/news/canada/manitoba/manitoba-dig-uncovers-80-million-year-old-sea-creature-1.711525 |work=CBC |location=Manitoba |archive-url=https://web.archive.org/web/20180605122916/https://www.cbc.ca/news/canada/manitoba/manitoba-dig-uncovers-80-million-year-old-sea-creature-1.711525|archive-date=June 5, 2018}}</ref><ref>{{cite journal|author1=Bullard, T.S.|author2=Caldwell, M.W.|year=2010|title=Redescription and rediagnosis of the tylosaurine mosasaur ''Hainosaurus pembinensis'' Nicholls, 1988, as ''Tylosaurus pembinensis'' (Nicholls, 1988)|journal=Journal of Vertebrate Paleontology|volume=30|issue=2|pages=416–426|doi=10.1080/02724631003621870|bibcode=2010JVPal..30..416B |s2cid=86297189}}</ref>

Mosasaurs had a body shape similar to that of modern-day [[monitor lizard]]s (varanids), but were more elongated and streamlined for swimming. Their limb bones were reduced in length and their paddles were formed by webbing between their long finger and toe bones. Their tails were broad, and supplied their locomotive power.

Until recently, mosasaurs were assumed to have swum in a method similar to the one used today by [[conger eel]]s and [[sea snake]]s, undulating their entire bodies from side to side. However, new evidence suggests that many advanced mosasaurs had large, crescent-shaped flukes on the ends of their tails, similar to those of [[shark]]s and some [[ichthyosaur]]s. Rather than use snake-like undulations, their bodies probably remained stiff to reduce drag through the water, while their tails provided strong propulsion.<ref name=LCKC10>{{cite journal |last=Lindgren |first=J. |author2=Caldwell, M.W. |author3=Konishi, T. |author4= Chiappe, L.M. |year=2010 |editor1-last=Farke |editor1-first=Andrew Allen |title=Convergent Evolution in Aquatic Tetrapods: Insights from an Exceptional Fossil Mosasaur |journal=PLOS ONE |pmid=20711249 |volume=5 |issue=8 |pmc=2918493 |pages=e11998 |doi=10.1371/journal.pone.0011998|bibcode=2010PLoSO...511998L |doi-access=free }}</ref> These animals may have lurked and pounced rapidly and powerfully on passing prey, rather than chasing after it.<ref>{{Cite journal | last1 = Lindgren | first1 = J. | last2 = Kaddumi | first2 = H. F. | last3 = Polcyn | first3 = M. J. | title = Soft tissue preservation in a fossil marine lizard with a bilobed tail fin | doi = 10.1038/ncomms3423 | journal = Nature Communications | volume = 4 | year = 2013 | pmid =  24022259| page=2423| bibcode = 2013NatCo...4.2423L | doi-access = free }}</ref> At least some species were also capable of aquaflight, flapping their flippers like [[sea lion]]s.<ref>{{cite journal |last1=Nicholls |first1=Elizabeth L. |first2=Stephen J. |last2=Godfrey |title=Subaqueous Flight in Mosasaurs: A Discussion |journal=Journal of Vertebrate Paleontology |volume=14 |issue=3 |year=1994 |pages=450–452 |doi=10.1080/02724634.1994.10011570 |jstor=4523581|bibcode=1994JVPal..14..450N }}</ref><ref>Reassessment of the Mosasaur Pectoral Girdle and its Role in Aquatic Locomotion, gsa.confex.com/gsa/2019AM/webp ... ram/Paper333823.html</ref>

Early reconstructions showed mosasaurs with dorsal crests running the length of their bodies, which were based on misidentified remains of [[trachea]]l cartilage. By the time this error was discovered, depicting mosasaurs with such crests in artwork had already become a trend.<ref>{{cite journal |url=http://oceansofkansas.com/Osborn1899.html |journal=Memoirs of the American Museum of Natural History |issue=4 |volume=1 |pages=167–188 |title=A Complete Mosasaur Skeleton, Osseous and Cartilaginous |first=Henry Fairfield |last=Osborn |year=1899 |access-date=25 November 2014|bibcode=1899Sci....10..919O |doi=10.1126/science.10.260.919 |pmid=17837338 |hdl=2027/mdp.39015042532336 |hdl-access=free }}</ref><ref>{{cite web |url= http://oceansofkansas.com/Williston98.html |title=Origin of the Dorsal Fringe on Mosasaurs |first=Mike |last=Everhart |work=Oceans of Kansas |date=13 January 2013 |access-date=25 November 2014}}</ref>

==Paleobiology==
[[File:Placenticeratidae - Placenticeras whitfieldi.jpg|thumb|Fossil shell of ammonite ''[[Placenticeras whitfieldi]]'' showing punctures caused by the bite of a mosasaur, [[Peabody Museum of Natural History]], Yale]]
[[File:Mosasaur tooth.jpg|thumb|A tooth from a mosasaur]]
Mosasaurs had double-hinged jaws and flexible skulls (much like those of [[snake]]s), which enabled them to gulp down their prey almost whole. A skeleton of ''[[Tylosaurus]] proriger'' from [[South Dakota]] included remains of the diving [[seabird]] ''[[Hesperornis]]'', a marine [[bony fish]], a possible [[shark]], and another, smaller mosasaur (''Clidastes''). Mosasaur bones have also been found with shark teeth embedded in them.

One of the food items of mosasaurs were [[ammonites]], molluscs with shells similar to those of ''[[Nautilus]]'', which were abundant in the Cretaceous seas. Holes have been found in fossil shells of some ammonites, mainly ''[[Pachydiscus]]'' and ''[[Placenticeras]]''. These were once interpreted as a result of limpets attaching themselves to the ammonites, but the triangular shape of the holes, their size, and their presence on both sides of the shells, corresponding to upper and lower jaws, is evidence of the bite of medium-sized mosasaurs. Whether this behaviour was common across all size classes of mosasaurs is not clear.

Virtually all forms were active predators of fish and ammonites; a few, such as ''[[Globidens]]'', had blunt, spherical teeth, specialized for crushing mollusk shells. The smaller genera, such as ''[[Platecarpus]]'' and ''[[Dallasaurus]]'', which were about {{convert|1|–|6|m|ft|abbr=on}} long, probably fed on fish and other small prey. The smaller mosasaurs may have spent some time in fresh water, hunting for food. The largest mosasaur ''Mosasaurus hoffmannii'' was the [[apex predator]] of the Late Cretaceous oceans, reaching more than {{convert|11|m|ft}} in length and weighing up to {{convert|10|MT|ST}} in body mass.<ref>{{cite journal|author1=Fedrico Fanti|author2=Andrea Cau|author3=Alessandra Negri|title=A giant mosasaur (Reptilia, Squamata) with an unusually twisted dentition from the Argille Scagliose Complex (late Campanian) of Northern Italy|year=2014|journal=Cretaceous Research|volume=49|issue=2014|pages=91–104|doi=10.1016/j.cretres.2014.01.003|bibcode=2014CrRes..49...91F |url=https://www.disva.univpm.it/sites/www.disva.univpm.it/files/disva/news_dipartimento/cretaceus%20research.pdf}}</ref>

===Soft tissue===
[[Image:Tylosaurus skin.jpg|thumb|left|Scales of ''Tylosaurus proriger'' (KUVP-1075)]]
Despite the many mosasaur remains collected worldwide, knowledge of the nature of their skin coverings remains in its early stages. Few mosasaurid specimens collected from around the world retain fossilized scale imprints. This lack may be due to the delicate nature of the scales, which nearly eliminates the possibility of preservation, in addition to the preservation sediment types and the marine conditions under which the preservation occurred. Until the discovery of several mosasaur specimens with remarkably well-preserved scale imprints from late [[Maastrichtian]] deposits of the Muwaqqar Chalk Marl Formation of [[Harrana]]<ref name=Kaddumi>{{cite book |last=Kaddumi |first=H.F. |year=2009 |chapter=On the latest scale coverings of mosasaurs (Squamata: ''Mosasauridae'') from the Harrana Fauna in addition to the description of s new species of Mosasaurus |title=Fossils of the Harrana Fauna and the Adjacent Areas |publisher=Eternal River Museum of Natural History |location=[[Amman]] |pages=80–94}}</ref> in [[Jordan]], knowledge of the nature of mosasaur integument was mainly based on very few accounts describing early mosasaur fossils dating back to the upper [[Santonian]]–lower [[Campanian]], such as the famous ''[[Tylosaurus]]'' specimen (KUVP-1075) from Gove County, Kansas.<ref name=Snow>{{cite journal |last=Snow |first=F. H. |year=1878 |title=On the dermal covering of a mosasauroid reptile |journal=Transactions of the Kansas Academy of Science |volume=6 |pages=54–58 |doi=10.2307/3623557 |jstor=3623557 }}</ref>

Material from Jordan has shown that the bodies of mosasaurs, as well as the membranes between their fingers and toes, were covered with small, overlapping, diamond-shaped scales resembling those of snakes. Much like those of modern reptiles, mosasaur scales varied across the body in type and size. In Harrana specimens, two types of scales were observed on a single specimen: keeled scales covering the upper regions of the body and smooth scales covering the lower.<ref name=Kaddumi/> As ambush predators, lurking and quickly capturing prey using stealth tactics,<ref name=Massare>{{cite journal |doi=10.1080/02724634.1987.10011647 |last=Massare |first=J. A. |year=1987 |title=Tooth morphology and prey preference of Mesozoic marine reptiles |journal=Journal of Vertebrate Paleontology |volume=7 |issue=2 |pages=121–137|bibcode=1987JVPal...7..121M }}</ref> they may have benefited from the nonreflective, keeled scales.<ref name=Kaddumi/> Additionally, mosasaurs had large pectoral girdles, and such genera as ''Plotosaurus'' may have used their front flippers in a breaststroke motion to gain added bursts of speed during an attack on prey.<ref>{{Cite web | url=https://www.sciencedaily.com/releases/2019/09/190923140812.htm |title = Did mosasaurs do the breast stroke?}}</ref> 
[[Image:Soft tissue structures in Platecarpus.png|thumb|Soft tissues in the head and neck of ''Platecarpus tympaniticus'' specimen LACM 128319: Tracheal rings are shown in the bottom three photographs.]]
More recently, a fossil of ''[[Platecarpus|Platecarpus tympaniticus]]'' has been found that preserved not only skin impressions, but also internal organs. Several reddish areas in the fossil may represent the heart, lungs, and kidneys. The trachea is also preserved, along with part of what may be the [[retina]] in the eye. The placement of the kidneys is farther forward in the abdomen than it is in monitor lizards, and is more similar to those of [[cetacean]]s. As in cetaceans, the [[bronchi]] leading to the lungs run parallel to each other instead of splitting apart from one another as in monitors and other terrestrial reptiles. In mosasaurs, these features may be internal adaptations to fully marine lifestyles.<ref name=LCKC10/>
[[File:Prognathodon tissue.jpg|thumb|left|Fibrous tissues and microstructures recovered from ''Prognathodon'' specimen IRSNB 1624]]

In 2011, [[collagen]] protein was recovered from a ''[[Prognathodon]]'' humerus dated to the [[Cretaceous]].<ref>{{Cite journal |last1=Lindgren |first1=Johan |last2=Uvdal |first2=Per |last3=Engdahl |first3=Anders |last4=Lee |first4=Andrew H. |last5=Alwmark |first5=Carl |last6=Bergquist |first6=Karl-Erik |last7=Nilsson |first7=Einar |last8=Ekström |first8=Peter |last9=Rasmussen |first9=Magnus |date=29 April 2011 |title=Microspectroscopic Evidence of Cretaceous Bone Proteins |journal=[[PLoS ONE]] |language=en |volume=6 |issue=4 |pages=e19445 |doi=10.1371/journal.pone.0019445 |issn=1932-6203 |pmc=3084868 |pmid=21559386 |first10=Desirée A. |last10=Douglas |first11=Michael J. |last11=Polcyn |first12=Louis L. |last12=Jacobs|bibcode=2011PLoSO...619445L |doi-access=free }}</ref>

In 2005, a [[case study]] by A.S. Schulp, E.W.A Mulder, and K. Schwenk outlined the fact that mosasaurs had paired [[fenestra]]e in their palates. In monitor lizards and snakes, paired fenestrae are associated with a [[forked tongue]], which is flicked in and out to detect chemical traces and provide a directional sense of [[Olfaction|smell]]. They therefore proposed that mosasaurs probably also had a sensitive forked tongue.<ref>{{Cite journal |last1=Schulp |first1=A. S. |last2=Mulder |first2=E. W. A. |last3=Schwenk |first3=K. |date=2005-09-01 |title=Did mosasaurs have forked tongues? |journal=Netherlands Journal of Geosciences |volume=84 |issue=3 |pages=359–371 |doi=10.1017/S0016774600021144 |doi-access=free |bibcode=2005NJGeo..84..359S }}</ref>

===Metabolism===
A study published in 2016 by T. Lyn Harrell, Alberto Pérez-Huerta and [[Celina A. Suarez|Celina Suarez]] showed that mosasaurs were [[endotherm]]ic. The study contradicted findings published in 2010 indicating mosasaurs were [[ectotherm]]ic. The 2010 study did not use warm-blooded animals for comparison but analogous groups of common marine animals. Based on comparisons with modern warm-blooded animals and fossils of known cold-blooded animals from the same time period, the 2016 study found mosasaurs likely had body temperatures similar to those of contemporary seabirds and were able to internally regulate their temperatures to remain warmer than the surrounding water.<ref>{{cite journal |last1=Harrell |first1=T. Lynn |last2=Pérez-Huerta |first2=Alberto |last3=Suarez |first3=Celina A. |last4=Benson |first4=Roger |title=Endothermic mosasaurs? Possible thermoregulation of Late Cretaceous mosasaurs (Reptilia, Squamata) indicated by stable oxygen isotopes in fossil bioapatite in comparison with coeval marine fish and pelagic seabirds |journal=Palaeontology |date=May 2016 |volume=59 |issue=3 |pages=351–363 |doi=10.1111/pala.12240|s2cid=130190966 |doi-access=free |bibcode=2016Palgy..59..351H }}
*{{cite press release |date=May 6, 2016 |title=Scientists cite evidence that mosasaurs were warm-blooded |website=ScienceDaily |url=https://www.sciencedaily.com/releases/2016/05/160506160429.htm}}</ref>

===Coloration===
The coloration of mosasaurs was unknown until 2014, when the findings of Johan Lindgren of [[Lund University]] and colleagues revealed the pigment [[melanin]] in the fossilized scales of a mosasaur. Mosasaurs were likely [[countershaded]], with dark backs and light underbellies, much like a [[great white shark]] or [[leatherback sea turtle]], the latter of which had fossilized ancestors for which color was also determined. The findings were described in ''[[Nature (journal)|Nature]]''.<ref>{{Cite journal |last1=Lindgren |first1=J. |last2=Sjövall |first2=P. |last3=Carney |first3=R. M. |last4=Uvdal |first4=P. |last5=Gren |first5=J. A. |last6=Dyke |first6=G. |last7=Schultz |first7=B. P. |last8=Shawkey |first8=M. D. |last9=Barnes |first9=K. R. |year=2014 |title=Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles |journal=Nature |volume=506 |issue=7489 |pages=484–8 |doi=10.1038/nature12899 |pmid=24402224 |last10=Polcyn |first10=M. J.|bibcode=2014Natur.506..484L |s2cid=4468035 }}</ref>

===Teeth===
Mosasaurs possessed a [[Thecodont dentition|thecodont dentiton]], meaning that the roots were cemented deeply into the jaw bone. Mosasaurs did not use permanent teeth but instead constantly shed them. Replacement teeth developed within a pit inside the roots of the original tooth called the resorption pit. This is done through a distinctively unique eight-stage process. The first stage was characterized by the mineralization of a small tooth crown developed elsewhere that descended into the resorption pit by the second stage. In the third stage, the developing crown firmly cemented itself within the resorption pit and grew in size; by the fourth stage, it would be of the same size as the crown in the original tooth. Stages five and six were characterized by the development of the replacement tooth's root: in stage five the root developed vertically, and in stage six the root expanded in all directions to the point that the replacement tooth became exposed and actively pushed on the original tooth. In the seventh stage, the original tooth was shed and the now-independent replacement tooth began to anchor itself into the vacancy. In the eighth and final stage, the replacement tooth has grown to firmly anchor itself.<ref name=CaldwellDentition>{{cite journal|author1=Michael W. Caldwell|title=Ontogeny, anatomy and attachment of the dentition in mosasaurs (Mosasauridae: Squamata)|year=2007|journal=Zoological Journal of the Linnean Society|volume=149|issue=4|pages=687–700|doi=10.1111/j.1096-3642.2007.00280.x|doi-access=free}}</ref>

===Ontogeny and growth===
Mosasaur growth is not well understood, as specimens of juveniles are rare, and many were mistaken for hesperornithine birds when discovered 100 years ago. However, the discovery of several specimens of juvenile and neonate-sized mosasaurs unearthed more than a century ago indicate that mosasaurs gave birth to live young, and that they spent their early years of life out in the open ocean, not in sheltered nurseries or areas such as shallow water as previously believed. Whether mosasaurs provided parental care, like other marine reptiles such as plesiosaurs, is currently unknown. The discovery of young mosasaurs was published in the journal ''Palaeontology''.<ref>{{Cite news|url=https://www.sciencedaily.com/releases/2015/04/150410113408.htm|title=What life was like for newborn giant sea lizards during the age of the dinosaur|work=ScienceDaily|access-date=2017-08-01|language=en}}</ref>

=== Possible eggs ===
A 2020 study published in [[Nature (journal)|''Nature'']] described a large fossilized hatched egg from [[Antarctica]] from the very end of the [[Cretaceous]], about 68 million years ago. The egg is considered one of the largest [[amniote]] eggs ever known, rivalling that of the [[elephant bird]], and due to its soft, thin, folded texture, it likely belonged to a marine animal. While the organism that produced it remains unknown, the egg's pore structure is very similar to that of extant [[Lepidosauria|lepidosaurs]] such as lizards and snakes, and presence of mosasaur fossils nearby indicates that it may have been a mosasaur egg. It is unknown whether the egg was laid on land or in the water. The egg was assigned to the newly described [[Egg fossil|oospecies]] ''[[Antarcticoolithus bradyi]]''.<ref>{{Cite news|date=2020-06-17|title=Mystery egg likely 'belonged to giant sea reptile'|language=en-GB|work=BBC News|url=https://www.bbc.com/news/science-environment-53085318|access-date=2020-06-18}}</ref><ref>{{Cite news|last=Joel|first=Lucas|date=2020-06-17|title=Life Hatched From Soft Eggs, Some a Foot Long, in Dinosaur Era|language=en-US|work=The New York Times|url=https://www.nytimes.com/2020/06/17/science/dinosaurs-soft-eggs.html|access-date=2020-06-18|issn=0362-4331}}</ref><ref>{{Cite journal|last1=Legendre|first1=Lucas J.|last2=Rubilar-Rogers|first2=David|last3=Musser|first3=Grace M.|last4=Davis|first4=Sarah N.|last5=Otero|first5=Rodrigo A.|last6=Vargas|first6=Alexander O.|last7=Clarke|first7=Julia A.|date=2020-06-17|title=A giant soft-shelled egg from the Late Cretaceous of Antarctica|journal=Nature|volume=583|issue=7816|language=en|pages=411–414|doi=10.1038/s41586-020-2377-7|pmid=32555453|bibcode=2020Natur.583..411L|issn=1476-4687|doi-access=free}}</ref> However, it has been proposed that this egg belonged to a dinosaur.<ref>{{Cite journal |last=Lindgren |first=Johan |last2=Kear |first2=Benjamin P. |date=July 2020 |title=Hard evidence from soft fossil eggs |url=https://www.nature.com/articles/d41586-020-01732-8 |journal=Nature |language=en |volume=583 |issue=7816 |pages=365–366 |doi=10.1038/d41586-020-01732-8|url-access=subscription }}</ref>

==Environment==
Paleontologists compared the taxonomic diversity and patterns of morphological disparity in mosasaurs with sea level, [[sea surface temperature]], and stable carbon isotope curves for the Upper Cretaceous to explore factors that may have influenced their evolution. No single factor unambiguously accounts for all radiations, diversification, and extinctions; however, the broader patterns of taxonomic diversification and morphological disparity point to niche differentiation in a "fishing up" scenario under the influence of "bottom-up" selective pressures. The most likely driving force in mosasaur evolution was high productivity in the Late Cretaceous, driven by tectonically controlled sea levels and climatically controlled [[ocean stratification]] and nutrient delivery. When productivity collapsed at the end of the Cretaceous, coincident with bolide impact, mosasaurs became extinct.<ref>{{cite journal | last1 = Polcyn | first1 = M. J. | last2 = Jacobs | first2 = L. L. | last3 = Araujo | first3 = R. | last4 = Schulp | first4 = A. S. | last5 = Mateus | first5 = O. | year = 2014 | title = Physical drivers of mosasaur evolution | journal = Palaeogeography, Palaeoclimatology, Palaeoecology | volume = 400 | pages = 17–27 | doi=10.1016/j.palaeo.2013.05.018| bibcode = 2014PPP...400...17P }}</ref>
[[File:Fragment čelisti mosasaura z Dolního Újezda u Litomyšle.jpg|thumb|Fossil jaw fragment of a mosasaurid reptile from Dolní Újezd by [[Litomyšl]], [[Czech Republic]]]]

Sea levels were high during the Cretaceous period, causing marine transgressions in many parts of the world, and a [[Western Interior Seaway|great inland seaway]] in what is now North America. Mosasaur [[fossil]]s have been found in the [[Netherlands]], [[Belgium]], [[Denmark]], [[Portugal]], [[Sweden]], [[South Africa]], [[Spain]], [[France]], [[Germany]], [[Poland]], the [[Czech Republic]], [[Italy]]<ref>{{Cite web|url=https://dinosaurusblog.com/2015/07/13/druhohorni-plazi-v-cechach-ii/|title=Druhohorní plazi v Čechách II.|date=2015-07-13|website=DinosaurusBlog|access-date=2017-08-01}}</ref> [[Bulgaria]], the [[United Kingdom]],<ref>{{cite web |url=https://www.english-nature.org.uk/citation/citation_photo/2000158.pdf |title=St. James' Pit, Norwich (SSSI) |work=[[Natural England]] |year=2014 |access-date=25 November 2014}}</ref><ref>{{Cite journal |last1= Jagt |first1=John W. M. |last2=Motchurova-Dekova |first2=Neda  |last3= Ivanov |first3=Plamen |last4=Cappetta |first4=Henri  |last5= Schulp |first5=Anne S. |year=2006 |title=Latest Cretaceous mosasaurs and lamniform sharks from Labirinta cave, Vratsa District (northwest Bulgaria): A preliminary note |journal=Geološki Anali Balkanskoga Poluostrva |volume=67 |issue=67 |pages=51–63 |doi=10.2298/gabp0667051j|doi-access=free }}</ref> [[Russia]], [[Ukraine]], [[Kazakhstan]], [[Azerbaijan]],<ref>{{Cite book |title=The age of dinosaurs in Russia and Mongolia |url=https://archive.org/details/agedinosaursruss00bent |url-access=limited |last1=Storrs |first1=Glenn W. |last2=Arkhangelskii |first2=Maxim S. |last3=Efimov |first3=Vladimir M. |publisher=Cambridge University Press |year=2000 |isbn=978-0521554763 |editor-last=Benton |editor-first=M. J. |location=Cambridge |pages=[https://archive.org/details/agedinosaursruss00bent/page/n224 187]–210 |chapter=Mesozoic marine reptiles of Russia and other former Soviet republics |editor-last2=Shishkin |editor-first2=M. A. |editor-last3=Unwin |editor-first3=D. M.}}</ref> [[Japan]],<ref>{{Cite journal |last1=Konishi |first1=Takuya |last2=Tanimoto |first2=Masahiro |last3=Utsunomiya |first3=Satoshi |last4=Sato |first4=Masahiro |last5=Watanabe |first5=Katsunori |year=2012 |title=A Large Mosasaurine (Squamata: Mosasauridae) from the Latest Cretaceous of Osaka Prefecture (SW Japan) |journal=Paleontological Research |volume=16 |issue=2 |pages=79–87 |doi=10.2517/1342-8144-16.2.079|s2cid=130109440 }}</ref> [[Egypt]], [[Israel]], [[Jordan]], [[Syria]],<ref name="NJGS2005Globidens">{{Cite journal |last1=Bardet |first1=Nathalie |last2=Pereda Suberbiola |first2=Xabier |last3=Iarochène |first3=Mohamed |last4=Amalik |first4=Mohamed |last5=Bouya |first5=Baadi |date=Sep 2005 |title=Durophagous Mosasauridae (Squamata) from the Upper Cretaceous phosphates of Morocco, with description of a new species of ''Globidens'' |journal=[[Netherlands Journal of Geosciences]] |language=en |volume=84 |issue=3 |pages=167–175 |doi=10.1017/S0016774600020953 |doi-access=free |bibcode=2005NJGeo..84..167B }}</ref> [[Turkey]],<ref>{{Cite journal |last1=Bardet |first1=Nathalie |last2=Tunoğlu |first2=Cemal |date=2002-09-19 |orig-date=24 Aug 2010<!--published online--> |title=The first mosasaur (Squamata) from the Late Cretaceous of Turkey |journal=Journal of Vertebrate Paleontology |language=en |volume=22 |issue=3 |pages=712–715 |doi=10.1671/0272-4634(2002)022[0712:TFMSFT]2.0.CO;2 |s2cid=130514699 |issn=0272-4634 |df=dmy}}</ref> [[Niger]],<ref>{{Cite journal |last= Lingham-Soliar |first=Theagarten |date=1991 |title=Mosasaurs from the upper Cretaceous of Niger |url=https://archive.org/details/biostor-165951 |journal=Palaeontology |volume=34 |issue=3 |pages=653–670 |via=BioStor}}</ref><ref>{{Cite journal |last=Lingham-Soliar |first=Theagarten  |date=1998 |title=A new mosasaur ''Pluridens walkeri'' from the Upper Cretaceous, Maastrichtian of the Iullemmeden Basin, southwest Niger |journal=Journal of Vertebrate Paleontology |volume=18 |issue=4 |pages=709–717 |doi=10.1080/02724634.1998.10011100|bibcode=1998JVPal..18..709L }}</ref> [[Angola]], [[Morocco]], [[Australia]], [[New Zealand]], and on [[Vega Island]] off the coast of [[Antarctica]]. Tooth taxon ''Globidens timorensis'' is known from the island of [[Timor]]; however, the phylogenetic placement of this species is uncertain and it might not even be a mosasaur.<ref>{{Cite book |title=The Geology and Paleontology of the Late Cretaceous Marine Deposits of the Dakotas |volume=427 |last=Martin |first=James E. |publisher=The Geological Society of America |year=2007 |editor-last=Martin |editor-first=James E. |pages=177–198 |chapter=A new species of the durophagous mosasaur, ''Globidens'' (Squamata: Mosasauridae) from the Late Cretaceous Pierre Shale Group of central South Dakota, USA |doi=10.1130/2007.2427(13) |editor-last2=Parris |editor-first2=David C.|isbn=978-0-8137-2427-0 }}</ref>

Mosasaurs have been found in [[Canada]] in [[Manitoba]] and [[Saskatchewan]]<ref>{{cite web |url= http://www.discoverfossils.com/ |title=General Information |work=Canadian Fossil Discovery Centre |year=2014 |access-date=25 November 2014}}</ref> and in much of the contiguous United States. Complete or partial specimens have been found in [[Alabama]], [[Mississippi]], [[New Jersey]], [[Tennessee]], and [[Georgia (U.S. state)|Georgia]], as well as in states covered by the Cretaceous seaway: [[Texas]], southwest [[Arkansas]], [[New Mexico]], [[Kansas]],<ref>{{cite book |author=Michael J. Everhart |title=Oceans of Kansas: a natural history of the western interior sea |publisher=Indiana University Press |location=Bloomington |year=2005 |isbn=978-0-253-34547-9 |chapter=Chapter 9: Enter the Mosasaurs}}</ref> [[Colorado]], [[Nebraska]], [[South Dakota]], [[Montana]], [[Wyoming]], and the [[Pierre Shale]]/[[Fox Hills Formation|Fox Hills]] formations of [[North Dakota]].<ref>{{Cite thesis |last=Getman |first=Myron |title=Occurrences of Mosasaur and other reptilian fossil remains from the Fox Hills Formation (Maastrichtian: late Cretaceous) of North Dakota |date=1994 |degree=Geology Honors |publisher=St. Lawrence University Dept. of Geology}}</ref> Lastly, mosasaur bones and teeth are also known from [[Colombia]],<ref>{{Cite journal |last=Páramo-Fonseca |first=María Eurídice |date=2012-03-01 |title=Mosasauroids from Colombia |journal=Bulletin de la Société Géologique de France |language=en |volume=183 |issue=2 |pages=103–109 |doi=10.2113/gssgfbull.183.2.103 |issn=0037-9409 |via=GeoScienceWorld |df=dmy}}</ref> [[Brazil]],<ref name="NJGS2005Globidens" /> and [[Chile]].<ref>{{Cite journal |last1=Otero |first1=Rodrigo A. |last2=Parham |first2=James F. |last3=Soto-Acuña |first3=Sergio |last4=Jimenez-Huidobro |first4=Paulina |last5=Rubilar-Rogers |first5=David |year=2012 |title=Marine reptiles from Late Cretaceous (early Maastrichtian) deposits in Algarrobo, central Chile |journal=[[Cretaceous Research]] |volume=35 |pages=124–132 |doi=10.1016/j.cretres.2011.12.003|bibcode=2012CrRes..35..124O }}</ref>

Many of the so-called 'dinosaur' remains found on [[New Zealand]] are actually mosasaurs and [[plesiosaur]]s{{Citation needed|date=March 2020}}, both being Mesozoic predatory marine reptiles.

The largest mosasaur currently on public display is Bruce, a 65-70%-complete specimen of ''Tylosaurus pembinensis'' dating from the late [[Cretaceous]] Period, approximately 80 million years ago, and measuring 13.05&nbsp;m (42.815&nbsp;ft) from nose tip to tail tip. Bruce was discovered in 1974 north of Thornhill, Manitoba, Canada, and resides at the nearby [[Canadian Fossil Discovery Centre]] in [[Morden, Manitoba]]. Bruce was awarded the Guinness Record for the largest mosasaur on public display in 2014.<ref>{{cite web |title=Largest mosasaur on display |url=https://www.guinnessworldrecords.com/world-records/118041-largest-mosasaur-on-display |website=Guinness World Records|date=22 August 2014 }}</ref>

==Discovery==
{{see also|Timeline of mosasaur research}}
[[Image:Mosasaurus.jpg|thumb|The ''Mosasaurus hoffmannii'' skull found in Maastricht between 1770 and 1774]]
The first publicized discovery of a partial fossil mosasaur skull in 1764 by quarry workers in a subterranean gallery of a limestone quarry in [[Mount Saint Peter]], near the Dutch city of [[Maastricht]], preceded any major dinosaur fossil discoveries, but remained little known. However, a second find of a partial skull drew the [[Age of Enlightenment]]'s attention to the existence of fossilized animals that were different from any known living creatures. When the specimen was discovered between 1770 and 1774, [[Johann Leonard Hoffmann]], a surgeon and fossil collector, corresponded about it with the most influential scientists of his day, making the fossil famous. The original owner, though, was Godding, a canon of Maastricht cathedral.

When the French [[Wars of the French Revolution|revolutionary forces]] occupied Maastricht in 1794, the carefully hidden fossil was uncovered, after a reward, it is said, of 600 bottles of wine, and transported to Paris. After it had been earlier interpreted as a fish, a crocodile, and a sperm whale, the first to understand its lizard affinities was the Dutch scientist [[Adriaan Gilles Camper]] in 1799. In 1808, [[Georges Cuvier]] confirmed this conclusion, although ''le Grand Animal fossile de Maëstricht'' was not actually named ''Mosasaurus'' ('[[Meuse]] reptile') until 1822 and not given its full species name, ''Mosasaurus hoffmannii,'' until 1829. Several sets of mosasaur remains, which had been discovered earlier at Maastricht but were not identified as mosasaurs until the 19th century, have been on display in the [[Teylers Museum]], [[Haarlem]], procured from 1790.

The Maastricht [[limestone]] beds were rendered so famous by the mosasaur discovery, they have given their name to the final six-million-year epoch of the Cretaceous, the [[Maastrichtian]].

== Classification ==
===Relationship with modern squamates===
{{multiple image
 | align = right
 | total_width = 400
 | image1 = Komodo dragon (Varanus komodoensis).jpg
 | image2 = 2017.07.17.-17-Tiefer See oder Grubensee-Storkow (Mark)--Ringelnatter.jpg
 | footer = Scientists continue to debate on whether [[monitor lizard]]s (left) or [[snake]]s (right) are the closest living relatives of mosasaurs.
}}
{{See also|Mosasauria#Relation with snakes or monitor lizards}}

===Lower classifications===
[[Image:Aigialosaurus bucchichi.jpg|thumb|Restoration of [[Opetiosaurus|''Opetiosaurus bucchichi'']], a basal mosasauroid]]
[[Image:GlobidensDB2.jpg|thumb|Life restoration of a mosasaurine, ''[[Globidens alabamaensis]]'']]
[[Image:Plotosaurus ben1DB.jpg|thumb|Life restoration of a mosasaurine, ''[[Plotosaurus bennisoni]]'']]
[[Image:Tylosaurus pembinensis 1DB.jpg|thumb|Restoration of a tylosaurine, ''[[Tylosaurus pembinensis]]'']]

The traditional view of mosasaur evolution held that all paddle-limbed (hydropedal) mosasaurs originated from a single common ancestor with functional legs (plesiopedal). However, this was shaken with the discovery of ''[[Dallasaurus]]'', a plesiopedal mosasauroid more closely related to the Mosasaurinae than other mosasaurs. Bell and Polycn (2005) grouped these outside mosasaurs into two clades: the Russellosaurina, whose basal members include plesiopedal genera (Tethysaurinae) of their own and derived members consisting of the Plioplatecarpinae and Tylosaurinae; and the Halisauromorpha, containing the Halisaurinae. The placement of ''Dallasaurus'' suggested that the Russellosaurina and Halisauromorpha may have evolved a hydropedal form independently, the former through the tethysaurines, meaning that their placement within the Mosasauridae creates an unnatural [[polyphyly]] and thus potentially invalid.<ref name=Dallasaurus>{{cite journal|author1=Bell, G.L. Jr.|author2=Polcyn, M.J.|year=2005|title=''Dallasaurus turneri'', a new primitive mosasauroid from the Middle Turonian of Texas and comments on the phylogeny of the Mosasauridae (Squamata)|journal=Netherlands Journal of Geoscience|volume=84|issue=3|pages=177–194|url=https://www.researchgate.net/publication/27711031|doi=10.1017/S0016774600020965|doi-access=free|bibcode=2005NJGeo..84..177B }}</ref><ref name="Caldwell2012">{{cite journal
|author=Caldwell, M.W.
|title=A challenge to categories: "What, if anything, is a mosasaur?"
|year=2012
|journal=Bulletin de la Société Géologique de France
|volume=183
|issue=1
|pages=17–34
|doi=10.2113/gssgfbull.183.1.7}}</ref> Caldwell informally proposed in a 2012 publication that the definition of a mosasaur must thus be redefined into one that does not consider russellosaurines and halisauromorphs as true mosasaurs, but as an independent group of marine lizards.<ref name="Caldwell2012" />

However, phylogenetic studies of mosasaurs can be fickle, especially when wild card taxa like ''Dallasaurus'' remain poorly understood. For example, some studies such as a 2009 analysis by Dutchak and Caldwell instead found that ''Dallasaurus'' was ancestral to both russellosaurines and mosasaurines,<ref name=Dutchak>{{cite journal|author1=Dutchak, A.R.|author2=Caldwell, M.W.|year=2009|title=A redescription of ''Aigialosaurus'' (=''Opetiosaurus'') ''bucchichi'' (Kornhuber, 1901) (Squamata: Aigialosauridae) with comments on mosasauroid systematics|journal=Journal of Vertebrate Paleontology|volume=29|issue=2|pages=437–452|doi=10.1671/039.029.0206|bibcode=2009JVPal..29..437D |s2cid=86140123}}</ref> although results were inconsistent in later studies.<ref name=Simoesetal>{{cite journal|author1=Simoes, T.R.|author2=Vernygora, O.|author3=Paparella, I.|author4=Jimenez-Huidobro, P.|author5=Caldwell, M.W.|title=Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group|journal=PLOS ONE|year=2017|volume=12|issue=5|pages=e0176773|doi=10.1371/journal.pone.0176773|pmid=28467456|pmc=5415187|bibcode=2017PLoSO..1276773S|doi-access=free}}</ref> A 2017 study by Simoes ''et al.'' noted that utilization of different methods of phylogenetic analyses can yield different findings and ultimately found an indication that tethysaurines were a case of hydropedal mosasaurs reversing back to a plesiopedal condition rather than an independent ancestral feature.<ref name=Simoesetal />

The following cladograms illustrate the two views of mosasaur evolution. Topology A follows an ancestral state reconstruction from an implied weighted maximum parsimony tree by Simoes et al. (2017), which contextualizes a single marine origin with tethysaurine reversal.<ref name=Simoesetal /> Topologies B and C illustrate the multiple-origins hypothesis of hydropedality; the former follows Makádi et al. (2012),<ref name=Makadietal2012>{{Cite journal | last1 = Makádi | first1 = L. S. | last2 = Caldwell | first2 = M. W. | last3 = Ősi | first3 = A.|editor1-link=Richard J. Butler | editor1-last = Butler | editor1-first = Richard J | title = The First Freshwater Mosasauroid (Upper Cretaceous, Hungary) and a New Clade of Basal Mosasauroids | doi = 10.1371/journal.pone.0051781 | journal = PLOS ONE | volume = 7 | issue = 12 | pages = e51781 | year = 2012 | pmid =  23284766| pmc = 3526648| bibcode = 2012PLoSO...751781M | doi-access = free }} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a Creative Commons License.</ref> while the latter follows a PhD dissertation by Mekarski (2017) that experimentally includes dolichosaur and poorly-represented aigialosaur taxa.<ref name=Merkarski2017>{{cite thesis|author=Mekarski, M.M.|title=The Origin and Evolution of Aquatic Adaptations in Cretaceous Squamates|year=2017|type=PhD|publisher=University of Alberta|url=https://era.library.ualberta.ca/items/41d1bd61-b71d-464f-a292-01c3018ea775|doi=10.7939/R3KK94S2B|doi-access=free}}</ref> Placement of major group names follow definitions by Madzia and Cau (2017).<ref>{{Cite journal|last1=Madzia|first1=Daniel|last2=Cau|first2=Andrea|date=2017-09-15|title=Inferring 'weak spots' in phylogenetic trees: application to mosasauroid nomenclature|journal=PeerJ|language=en|volume=5|pages=e3782|doi=10.7717/peerj.3782|pmid=28929018|pmc=5602675|issn=2167-8359|doi-access=free}}</ref>

{{clade gallery |width=450px |height=600px
|caption1=Topology A:
|header1=Ancestral state reconstruction by Simoes et al. (2017)
|cladogram1={{clade| style=font-size:85%;line-height:85%|style1=background-color:#ffca8a;
|1={{clade
   |1=''[[Adriosaurus|Adriosaurus suessi]]''
   |2={{clade
      |1=''[[Dolichosaurus|Dolichosaurus longicollis]]''
      |2={{clade
         |1={{clade
            |1=''[[Komensaurus|Komensaurus carrolli]]''
            |2={{clade
               |1=''[[Pontosaurus|Pontosaurus kornhuberi]]''
               |2={{clade
                  |1=''[[Aigialosaurus|Aigialosaurus dalmaticus]]''
                  |2=''[[Opetiosaurus|Opetiosaurus bucchichi]]''
                  }}
               }}
            }}
         |style2=background-color:#ffa1a1;
         |2={{clade
            |1={{clade
               |1='''[[Halisaurinae]]'''
               |label2='''[[Russellosaurina]]'''
               |2={{clade
                  |2={{clade
                     |1=[[Tylosaurinae]]
                     |2=[[Plioplatecarpinae]]
                     }}
                  |style1=background-color:#f5f5f5;
                  |1={{clade
                     |1={{clade
                        |1=''[[Yaguarasaurus|Yaguarasaurus columbianus]]''
                        |2={{clade
                           |1=''[[Russellosaurus|Russellosaurus coheni]]''
                           |2=''[[Romeosaurus|Romeosaurus fumanensis]]''
                           }}
                        }}
                     |style2=background-color:#ffca8a;
                     |2={{clade
                        |1=''[[Tethysaurus|Tethysaurus nopcsai]]''
                        |2=''[[Pannoniasaurus|Pannoniasaurus inexpectatus]]''
                        }}
                     }}
                  }}
               }}
            |label2='''[[Mosasaurinae]]'''
            |2={{clade|style1=background-color:#f5f5f5;
               |1=''[[Dallasaurus|Dallasaurus turneri]]''
               |2={{clade
                  |1=''[[Clidastes]]''
                  |2=Derived mosasaurines
                  }}
               }}
            }}
         }}
      }}
   }}
}}
<br />
{{legend|#ffca8a|[[Iliac crest]] attached to [[sacrum|sacral ribs]]|outline=gray}}
{{legend|#ffa1a1|Free-standing iliac crest|outline=gray}}
{{legend|#f5f5f5|Ambiguous state|outline=gray}}
|caption2=Topology B:
|header2=Strict consensus of maximum parsimony by Makádi et al. (2012)
|cladogram2={{clade| style=font-size:85%;line-height:85%
|1={{clade
   |1=''[[Varanus|Varanus spp.]]''
   |style2=background-color:#ffca8a;
   |2={{clade
      |1=''[[Aigialosaurus]]''
      |2={{clade
         |label1='''[[Russellosaurina]]'''
         |1={{clade
            |1={{clade
               |1=''[[Pannoniasaurus|Pannoniasaurus inexpectatus]]''
               |2={{clade
                  |1=''[[Tethysaurus|Tethysaurus nopcsai]]''|style2=background-color:#f5f5f5;
                  |2={{clade
                     |1=''[[Yaguarasaurus|Yaguarasaurus columbianus]]''
                     |2=''[[Russellosaurus|Russellosaurus coheni]]''
                     }}
                  }}
               }}
            |2={{clade
               |1=''[[Carsosaurus|Carsosaurus marchesetti]]''
               |2=''[[Komensaurus|Komensaurus carrolli]]''
               |3={{clade
                  |1=''[[Haasiasaurus|Haasiasaurus gittelmani]]''
                  |style2=background-color:#ffa1a1;
                  |2={{clade
                     |1='''[[Halisaurinae]]'''
                     |2={{clade
                        |1=[[Tylosaurinae]]
                        |2=[[Plioplatecarpinae]]
                        }}
                     }}
                  }}
               }}
            }}
         |label2='''[[Mosasaurinae]]'''
         |2={{clade
            |style1=background-color:#d9d9ff;
            |1=''[[Dallasaurus turneri]]''
            |style2=background-color:#ffa1a1;
            |2={{clade
               |1=''[[Clidastes]]''
               |2={{clade
                  |1={{clade
                     |1=[[Globidensini]]
                     |2=[[Prognathodontini]]
                     }}
                  |2=[[Mosasaurini]]
                  }}
               }}
            }}
         }}
      }}
   }}
}}
<br />
{{legend|#ffca8a|Plesiopedal and plesiopelvic taxa|outline=gray}}
{{legend|#d9d9ff|Plesiopedal and hydropelvic taxa|outline=gray}}
{{legend|#ffa1a1|Hydropedal and hydropelvic taxa|outline=gray}}
{{legend|#f5f5f5|Taxa with unknown limb structure|outline=gray}}
|caption3=Topology C:
|header3=Maximum clade credibility tree by Mekarski (2017)
|cladogram3={{clade| style=font-size:85%;line-height:60%
|1={{clade
   |1={{clade
     |1=''[[Varanus|Varanus spp.]]''
     |2={{clade|style1=background-color:#bbFFbb;|style2=background-color:#bbFFbb;|style3=background-color:#bbFFbb;|style4=background-color:#bbFFbb;
      |1={{clade
         |1=''[[Aigialosaurus|Aigialosaurus dalmaticus]]''
         |2=''[[Opetiosaurus|Opetiosaurus bucchichi]]''
         }}
      |2=''[[Komensaurus|Komensaurus carrolli]]''
      |3=''[[Haasiasaurus|Haasiasaurus gittelmani]]''
      |4={{clade|style1=background-color:#eeccFF;|style2=background-color:#eeccFF;
         |1='''[[Halisaurinae]]'''
         |label2='''[[Russellosaurina]]'''
         |2={{clade
            |1={{clade
               |1=''[[Tethysaurus|Tethysaurus nopcsai]]''
               |2=''[[Russellosaurus|Russellosaurus coheni]]''
               }}
            |2={{clade
               |1=''[[Yaguarasaurus columbianus]]''
               |2={{clade
                  |1=[[Tylosaurinae]]
                  |2=[[Plioplatecarpinae]]
                  }}
               }}
            }}
         }}}}
      }}
   |label2='''[[Mosasaurinae]]'''
   |2={{clade
      |style1=background-color:#bbedFF;
      |1={{clade
         |1={{clade
            |1=''[[Adriosaurus|Adriosaurus skrbinensis]]''
            |2={{clade
               |1=''[[Acteosaurus|Acteosaurus tommasinii]]''
               |2=''[[Pontosaurus]]''
               }}
            }}
         |2={{clade
            |1=''[[Mesoleptos|Mesoleptos zendrinii]]''
            |2={{clade
               |1=''[[Adriosaurus|Adriosaurus microbranchis]]''
               |2={{clade
                  |1=''[[Adriosaurus|Adriosaurus suessi]]''
                  |2=''[[Dolichosaurus|Dolichosaurus longicollis]]''
                  }}
               }}
            }}
         }}
      |style2=background-color:#bbFFbb;
      |2={{clade
         |1=''[[Carsosaurus|Carsosaurus marchesetti]]''
         |2={{clade
            |1=''[[Eidolosaurus|Eidolosaurus trauthi]]''|style1=background-color:#bbedFF;
            |2={{clade
               |1=''[[Portunatasaurus|Portunatasaurus krambergeri]]''
               |2={{clade
                  |1=''[[Vallecillosaurus|Vallecillosaurus donrobertoi]]''
                  |2={{clade
                     |1=''[[Dallasaurus|Dallasaurus turneri]]''
                     |2={{clade|style1=background-color:#eeccFF;|style2=background-color:#eeccFF;
                        |1=''[[Clidastes]]''
                        |2={{clade
                           |1=[[Prognathodontini]]
                           |2=[[Mosasaurini]]
                           }}
                        }}
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
}}
<br />
{{legend|#bbedFF|'[[Dolichosauridae|Dolichosaur]]' taxa|outline=gray}}
{{legend|#bbFFbb|'[[Aigialosauridae|Aigialosaur]]' taxa|outline=gray}}
{{legend|#eeccFF|Mosasaur taxa|outline=gray}}
}}<!-- end clade gallery-->

===Phylogeny===
{{See also|List of mosasaurs}}
The following diagram illustrates simplified phylogenies of the three major mosasaur groups as recovered by Strong et al. (2020), Longrich et al. (2021), and Longrich et al. (2022).

{{clade gallery |width=500px |height=450px
|caption1=[[Russellosaurina]]
|header1=Implied weighting maximum parsimony by Strong et al. (2020)<ref name=Strongetal2020>{{Cite journal|last1=Strong|first1=Catherine R. C.|last2=Caldwell|first2=Michael W.|last3=Konishi|first3=Takuya|last4=Palci|first4=Alessandro|year=2020|title=A new species of longirostrine plioplatecarpine mosasaur (Squamata: Mosasauridae) from the Late Cretaceous of Morocco, with a re-evaluation of the problematic taxon ''{{'}}Platecarpus{{'}} ptychodon''|journal=Journal of Systematic Palaeontology |volume=18 |issue=21 |pages=1769–1804 |doi=10.1080/14772019.2020.1818322|bibcode=2020JSPal..18.1769S }}</ref>
|cladogram1={{clade
|label1='''[[Russellosaurina]]'''
|1={{clade
   |label1=[[Yaguarasaurinae]]
   |1={{clade
      |1=''[[Yaguarasaurus]]'' [[File:Yaguarasaurus columbianus plioplatecarpine MP.png|50px]]
      |2={{clade
         |1=''[[Russellosaurus]]'' [[File:Russellosaurus.jpg|50px]]
         |2=''[[Romeosaurus]]''
         }}
      }}
   |2={{clade
      |label1=[[Tethysaurinae]]
      |1={{clade
         |1=''[[Tethysaurus]]''
         |2=''[[Pannoniasaurus]]'' [[File:Pannoniasaurus skeletal diagram.jpg|50px]]
         }}
      |2={{clade
         |label1=[[Tylosaurinae]]
         |1={{clade
            |1=''[[Taniwhasaurus]]'' <span style="{{MirrorH}}">[[File:Taniwhasaurus.jpg|50px]]</span>
            |2=''[[Tylosaurus]]'' <span style="{{MirrorH}}">[[File:Tylosaurus nepaeolicus NT.png|50px]]</span>
            }}
         |label2=[[Plioplatecarpinae]]
         |2={{clade
            |1=''[[Ectenosaurus]]'' [[File:Ectenosaurus.png|50px]]
            |2={{clade
               |1=''[[Plesioplatecarpus]]'' [[File:Plesioplatecarpus SW.png|50 px]]
               |2={{clade
                  |1={{clade
                     |1=''[[Angolasaurus]]'' [[File:Angolasaurus cráneo.png|50 px]]
                     |2={{clade
                        |1=''[[Goronyosaurus]]'' [[File:Goronyasaurus1DB.jpg|50px]]
                        |2={{clade
                           |1=''[[Selmasaurus]]'' <span style="{{MirrorH}}">[[File:Selmasaurus Clean.png|50px]]</span>
                           |2=''[[Gavialimimus]]''
                           }}
                        }}
                     }}
                  |2={{clade
                     |1=''[[Latoplatecarpus]]''
                     |2={{clade
                        |1=''[[Platecarpus]]'' [[File:Platecarpus tympaniticus.jpg|50px]]
                        |2=''[[Plioplatecarpus]]'' [[File:Plioplatecarpus primaevus life reconstruction.jpg|50px]]
                        }}
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
|style=font-size:85%;line-height:85%}}

|caption2=[[Halisaurinae]]
|header2=Strict consensus of maximum parsimony by Longrich et al., (2021)<ref name=Longrich2021>
Longrich, N. R., Bardet, N., Khaldoune, F., Yazami, O. K., & Jalil, N.-E. (2021). ''Pluridens serpentis'', a new mosasaurid (Mosasauridae: Halisaurinae) from the Maastrichtian of Morocco and implications for mosasaur diversity. Cretaceous Research, 104882.</ref>
|cladogram2={{clade
   |label1='''[[Halisaurinae]]'''
   |1={{clade
      |label1=[[Pluridens]]ini
      |1=''[[Pluridens]]'' <span style="{{MirrorH}}">[[File:Pluridens.png|50px]]</span>
      |label2=[[Halisaurinae|Halisaurini]]
      |2={{clade
         |1=''[[Eonatator]]''
         |2={{clade
            |1=''[[Phosphorosaurus]]'' [[File:Phosphorosaurus.png|50px]]
            |2=''[[Halisaurus]]'' <span style="{{MirrorH}}">[[File:Halisaurus arambourgi.jpg|50px]]</span>
            }}
         }}
      }}
|style=font-size:120%;line-height:120%}}

|caption3=[[Mosasaurinae]]
|header3=Maximum parsimony by Longrich et al. (2022)<ref name=LongrichThalassotitan>{{Cite journal |author1=Nicholas R. Longrich|author2=Nour-Eddine Jalil|author3=Fatima Khaldoune|author4=Oussama Khadiri Yazami|author5=Xabier Pereda-Suberbiola|author6=Nathalie Bardet|year=2022|title=''Thalassotitan atrox'', a giant predatory mosasaurid (Squamata) from the Upper Maastrichtian Phosphates of Morocco |url=https://www.sciencedirect.com/science/article/pii/S0195667122001793 |journal=[[Cretaceous Research]]|volume=140|pages=105315|doi=10.1016/j.cretres.2022.105315 |bibcode=2022CrRes.14005315L |s2cid=251821884 |issn=0195-6671}}</ref>
|cladogram3={{clade
   |label1='''[[Mosasaurinae]]'''
   |1={{clade
      |1=''[[Kourisodon]]'' <span style="{{MirrorH}}">[[File:Kourisodon puntledgensis life reconstruction.jpg|50px]]</span>
      |2={{clade
         |1=''[[Clidastes]]'' <span style="{{MirrorH}}">[[File:Clidastes proph1DB.jpg|50px]]</span>
         |2={{clade
            |1={{clade
               |1=''[[Eremiasaurus]]'' [[File:Eremiasaurus SW.png|50px]]
               |2={{clade
                  |label1=[[Globidensini]]
                  |1=''[[Globidens]]'' [[File:GlobidensDB2.jpg|50px]]
                  |label2=[[Prognathodontini]]
                  |2={{clade
                     |1=''[[Gnathomortis]]''
                     |2={{clade
                        |1=''[[Prognathodon]]'' <span style="{{MirrorH}}">[[File:Prognathodon saturator DB.jpg|50px]]</span>
                        |2=''[[Thalassotitan]]'' [[File:Thalassotitan atrox MP.png|50px]]
                        }}
                     }}
                  }}
               }}
            |label2=[[Mosasaurini]]
            |2={{clade
               |1=''[[Moanasaurus]]''
               |2={{clade
                  |1={{clade
                     |1=''[[Carinodens]]''
                     |2=''[[Xenodens]]''
                     }}
                  |2={{clade
                     |1=''[[Mosasaurus]]'' [[File:Mosasaurus 21copy.jpg|50px]]
                     |2={{clade
                        |1=''[[Plesiotylosaurus]]'' [[File:Plesiotylosaurus crassidens MP.jpg|50px]]
                        |2=''[[Plotosaurus]]'' [[File:Plotosaurus bennisoni profile reconstruction.jpg|50px]]
                        }}
                     }}
                  }}
               }}
            }}
         }}
      }}
}}
|style=font-size:85%;line-height:85%}}
<!-- end clade gallery-->

==Distribution==
{{main|List of mosasaur-bearing stratigraphic units}}Though no individual genus or subfamily is found worldwide, the Mosasauridae as a whole achieved global distribution during the [[Late Cretaceous]] with many locations typically having complex mosasaur faunas with multiple different genera and species in different [[ecological niche]]s.

Two African countries are particularly rich in mosasaurs: Morocco<ref>{{cite journal |last1=Bardet |first1=Nathalie |last2=Pereda Suberbiola |first2=Xabier |last3=Iarochene |first3=Mohamed |last4=Bouyahyaoui |first4=Fatima |last5=Bouya |first5=Baadi |last6=Amaghzaz |first6=Mbarek |title=Mosasaurus beaugei Arambourg, 1952 (Squamata, Mosasauridae) from the Late Cretaceous phosphates of Morocco |journal=Geobios |date=May 2004 |volume=37 |issue=3 |pages=315–324 |doi=10.1016/j.geobios.2003.02.006 |bibcode=2004Geobi..37..315B }}</ref> and Angola.<ref>{{cite journal |last1=Polcyn |first1=Michael J. |last2=Jacobs |first2=Louis L. |last3=Schulp |first3=Anne S. |last4=Mateus |first4=Octávio |title=The North African Mosasaur ''Globidens phosphaticus'' from the Maastrichtian of Angola |journal=Historical Biology |date=March 2010 |volume=22 |issue=1–3 |pages=175–185 |doi=10.1080/08912961003754978 |bibcode=2010HBio...22..175P |s2cid=62882332 }}</ref><ref>{{cite book |last1=Mateus |first1=Octávio |last2=Callapez |first2=Pedro M. |last3=Polcyn |first3=Michael J. |last4=Schulp |first4=Anne S. |last5=Gonçalves |first5=António Olímpio |last6=Jacobs |first6=Louis L. |chapter=The Fossil Record of Biodiversity in Angola Through Time: A Paleontological Perspective |title=Biodiversity of Angola: Science & Conservation: A Modern Synthesis |publisher=Springer International Publishing |pages=53–76 |language=en |doi=10.1007/978-3-030-03083-4_4 |date=2019 |isbn=978-3-030-03082-7 |s2cid=133717540 }}</ref>

==References==
{{reflist|22em}}

==External links==
{{external links|date=June 2021}}
{{Commons category|Mosasauridae}}
* [http://palaeos.com/vertebrates/squamata/pythonomorpha.html#Mosasauroidea Palaeos: Vertebrates: Mosasaurs]
* [http://www.bbc.co.uk/science/seamonsters/factfiles/giantmosasaur.shtml BBC Science and Nature: Mosasaurs]
* [http://www.oceansofkansas.com/nz-aus.html Mike Everhart and David Lewis, "Mesozoic marine monsters of the Mangahouanga"]: New Zealand fossil fauna
* [http://www.oceansofkansas.com/mosa-sty.html Mike Everhart, "A day in the life of a Mosasaur"]: life in the Sea of Kansas, illus. by Carl Buell
* [https://web.archive.org/web/20120511190327/http://www.oceansofkansas.com/mosahoff.html Mike Everhart, "''Mosasaurus hoffmani''"] until 1829.
* [https://web.archive.org/web/20071104232635/http://crossroads.journalismcentre.com/2007/the-mosasaur-of-maastricht/ "The Mosasaur of Maastricht"] by Hennie Reuvers in [https://web.archive.org/web/20060619133915/http://crossroads.journalismcentre.com/ Crossroads web magazine]
* [https://web.archive.org/web/20090803000703/http://planetearth.nerc.ac.uk/news/story.aspx?id=492 "Mosasaurs terrorized Cretaceous rivers" Planet Earth online]
* [https://books.google.com/books?id=3uNLAAAAMAAJ Kansas Geological Survey Vol IV (1899)], containing the famous summary of American mosasaurs by Samuel Williston.
* William R. Wahl * [https://web.archive.org/web/20130509085058/http://www.wyodino.org/wp-content/uploads/2011/01/BittenAmmonite.pdf MOSASAUR BITE MARKS ON AN AMMONITE. PRESERVATION OF AN ABORTED ATTACK? ]
* [http://palaeoart.blogspot.it/2011/10/mosasaur-diets-everhart-2004.html Mosasaur diet]

{{Mosasauridae}}
{{Portal bar|Paleontology|Reptiles|Marine life}}
{{Taxonbar|from1=Q729456}}

[[Category:Mosasaurs| 01]]
[[Category:Turonian first appearances]]
[[Category:Maastrichtian extinctions]]
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[[Category:Taxa named by Paul Gervais]] (Added in redirect pages [[Mosasauroidea]] and [[Mosasauridae]])
[[Category:Fossil taxa described in 1853]] (Added in redirect pages [[Mosasauroidea]] and [[Mosasauridae]]) -->