Paleontologists generally agree that Mosasaurus was likely an active predator of a variety of marine animals. [50] [61] Fauna likely preyed upon by the genus include bony fish, sharks, cephalopods, birds, and marine reptiles such as other mosasaurs [61] and turtles. [50] It is unlikely Mosasaurus was a scavenger as it had a poor sense of smell. Mosasaurus was among the largest marine animals of its time, [50] and with its large, robust cutting teeth, scientists believe larger members of the genus would have been able to handle virtually any animal. [61] Lingham-Soliar (1995) suggested that Mosasaurus had a rather "savage" feeding behavior as demonstrated by large tooth marks on scutes of the giant sea turtle Allopleuron hoffmanni and fossils of re-healed fractured jaws in M. hoffmannii. [50] The species likely hunted near the ocean surface as an ambush predator, using its large two-dimensionally adapted eyes to more effectively spot and capture prey. [50] Chemical and structural data in the fossils of M. lemonnieri and M. conodon suggests they may have also hunted in deeper waters. [88] a b David B. Kemp; Stuart A. Robinson; J. Alistair Crame; Jane E. Francis; Jon Ineson; Rowan J. Whittle; Vanessa Bowman; Charlotte O'Brien (2014). "A cool temperate climate on the Antarctic Peninsula through the latest Cretaceous to early Paleogene". Geology. 42 (7): 583–586. Bibcode: 2014Geo....42..583K. doi: 10.1130/g35512.1. The camera shows the computer screen, which is rotating around a 3D scan of the same fossil behind the scientists.

a b Vanessa C. Bowman; Jane E. Francis; James B. Riding (2013). "Late Cretaceous winter sea ice in Antarctica?" (PDF). Geology. 41 (12): 1227–1230. Bibcode: 2013Geo....41.1227B. doi: 10.1130/G34891.1. S2CID 128885087. Many of the earliest fossils of Mosasaurus were found in Campanian stage deposits in North America, including the Western Interior Seaway, an inland sea which once flowed through what is now the central United States and Canada, and connected the Arctic Ocean to the modern-day Gulf of Mexico. The region was shallow for a seaway, reaching a maximum depth of about 800–900 meters (2,600–3,000ft). [108] Extensive drainage from the neighboring continents, Appalachia and Laramidia, brought in vast amounts of sediment. Together with the formation of a nutrient-rich deepwater mass from the mixing of continental freshwater, Arctic waters from the north, and warmer saline Tethyan waters from the south, this created a warm and productive seaway that supported a rich diversity of marine life. [109] [110] [111]Louis Dollo (1889). "Première note sur les Mosasauriens de Mesvin". Bulletin de la Société belge de géologie, de paléontologie et d'hydrologie (in French). 3: 271–304. ISSN 0037-8909. M. lemonnieri is a controversial taxon, and there is debate on whether it is a distinct species or not. [37] In 1967, Dale Russell argued that M. lemonnieri and M. conodon are the same species and designated the former as a junior synonym per the principle of priority. [38] In a 2000 study, Lingham-Soliar refuted this based on a comprehensive study of existing M. lemonnieri specimens, [36] which was corroborated by a study on the M. conodon skull by Takehito Ikejiri and Spencer G. Lucas in 2014. [11] In 2004, Eric Mulder, Dirk Cornelissen, and Louis Verding suggested M. lemonnieri could be a juvenile form of M. hoffmannii based on the argument that significant differences could be explained by age-based variation. [39] However, the need for more research to confirm any hypotheses of synonymy was expressed. [40]

Andrew D. Gentry; James F. Parham; Dana J. Ehret; Jun A. Ebersole (2018). "A new species of Peritresius Leidy, 1856 (Testudines: Pan-Cheloniidae) from the Late Cretaceous (Campanian) of Alabama, USA, and the occurrence of the genus within the Mississippi Embayment of North America". PLOS ONE. 13 (4): e0195651. Bibcode: 2018PLoSO..1395651G. doi: 10.1371/journal.pone.0195651. PMC 5906092. PMID 29668704. Tamaki Sato (2005). "A new polycotylid plesiosaur (Reptilia: Sauropterygia) from the Upper Cretaceous Bearpaw Formation in Saskatchewan, Canada". Journal of Paleontology. 79 (5): 969–980. doi: 10.1666/0022-3360(2005)079[0969:anpprs]2.0.co;2. S2CID 131128997.Michael J. Everhart (January 1, 2010). "Mosasaur brain". Oceans of Kansas. Archived from the original on November 6, 2020. ZIETLOW: Mosasaurs would eat basically anything and everything that moved. We know that based on the shapes of their teeth, their actual stomach contents, and bite marks on other animals that lived with mosasaurs. Camera pans across a plastic model of what a mosasaur would have looked like alive, ending on the head with the mouth open wide.

a b c d e f James E. Martin (2006). "Biostratigraphy of the Mosasauridae (Reptilia) from the Cretaceous of Antarctica". Geological Society, London, Special Publications. 258 (1): 101–108. Bibcode: 2006GSLSP.258..101M. doi: 10.1144/gsl.sp.2006.258.01.07. S2CID 128604544.a b c Aaron R. H. LeBlanc; Michael W. Caldwell; Nathalie Bardet (2012). "A new mosasaurine from the Maastrichtian (Upper Cretaceous) phosphates of Morocco and its implications for mosasaurine systematics". Journal of Vertebrate Paleontology. 32 (1): 82–104. Bibcode: 2012JVPal..32...82L. doi: 10.1080/02724634.2012.624145. JSTOR 41407709. S2CID 130559113.