Mosasurs

mosasurs are not dinosaurs but acuatic reptiles the evoled from moniter lizerds to escape the greef of the dinosaurs, there not mamals they get fresh air.

they eat flying reptiles, fish ,sea birds turuels and dinos,

While there is little knowledge of the feeding habits of Mosasaurus, paleontologists generally agree that it was likely an active predator that preyed on a variety of marine animals. It is unlikely that Mosasaurus was a scavenger as it had a poor sense of smell. Mosasaurus was among the largest marine animals of its time, and with its large robust cutting teeth, scientists believe that larger members of the genus would have been able to handle virtually any animal. 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. Fauna that was likely preyed on by the mosasaur include bony fish, sharks, cephalopods, birds, and marine reptiles such as other mosasaurs and turtles. M. hoffmannii likely hunted near the ocean surface as an ambush predator, using its large two-dimensionally adapted eyes to more effectively spot and capture prey. Chemical and structural data in the fossils of M. lemonnieri and M. conodon suggests that they may have also hunted at deeper waters.

Carbon isotope studies on fossils of multiple M. hoffmannii individuals have found extremely low values of δ13C, the lowest in all mosasaurs. There are several implications for δ13C levels in the feeding ecology of mosasaurs. The relationship between δ13C levels in mosasaurs and their trophic levels are negatively correlated; mosasaurs with lower δ13C values tended to occupy higher trophic levels. One factor for this is dietary; a diet in prey with high lipid contents such as sea turtles and other large marine reptiles can lower δ13C values. With M. hoffmannii's low δ13C levels, this suggests that it likely fed on such prey and reinforces its likely position as an apex predator.

Currently, there is only one known example of a Mosasaurus preserved with stomach contents: a well-preserved partial skeleton of a small M. missouriensis dated about 75 million years ago (Ma). Analysis of its stomach contents have found the dismembered and punctured remains of a 1 meter (3.3 ft) long fish. This fish is much longer than the length of the mosasaur's skull, which was measured at 66 centimeters (26 in) in length, confirming that M. missouriensis was macrophagous and consumed prey larger than its head by dismembering and consuming bits at a time. The presence of other large mosasaurs which specialized in robust prey coexisting with the species strongly suggests that M. missouriensis likely specialized more on cutting-based prey (prey best fed on by teeth that have adapted to cutting) to ensure niche partitioning.

There is a possibility that Mosasaurus may have taught their offspring how to hunt, as supported by a fossil nautiloid Argonautilus catarinae with bite marks from two conspecific mosasaurs, one being from a juvenile and the other being from an adult. The positioning of both bite marks are at the direction that the nautiloid would have been facing, indicating that it was incapable of escaping and was thus already sick or dead during the attacks; it is possible that this phenomenon was from a parent mosasaur teaching its offspring that cephalopods were an alternate source of prey and how to hunt one. An alternate explanation is that the bite marks are from one individual mosasaur that lightly bit the nautiloid at first, then proceeded to bite again with greater force; but differences in tooth spacing between both bites indicate different jaw sizes, which makes the first hypothesis more likely. Analysis of the tooth marks have concluded that the mosasaurs were either Mosasaurus or Platecarpus.

Life history[edit]
Fragmentary skull of a juvenile Mosasaurus (NHMM 200793) from Geulhem, Netherlands

It is likely that Mosasaurus was viviparous (giving live birth) like modern mammals today. There is no evidence for live birth in Mosasaurus itself, but it is known in a number of other mosasaurs; examples include a skeleton of a pregnant basal mosasauroid Carsosaurus marchesetti, a Plioplatecarpus primaevus fossil associated with fossils of two mosasaur embryos, and fossils of newborn Clidastes from pelagic deposits. Such fossil records, along with a total absence of any evidence suggesting external egg-based reproduction, indicates the likeliness of Mosasaurus viviparity. Microanatomical studies on bones of juvenile Mosasaurus and related genera have found their bone structures are comparable to adults and did not exhibit bone mass increase (which is associated with a lifestyle in shallow water), signifying that Mosasaurus were already efficient swimmers and lived a fully functional lifestyle in open water at a very young age. These structures indicate that Mosasaurus was likely born precocial in pelagic settings and did not utilize nursery areas to birth and raise young. However, a number of localities in Europe and South Dakota have yielded concentrated assemblages of juvenile M. hoffmannii, M. missouriensis and/or M. lemonnieri. These localities are solely shallow ocean deposits, suggesting that juvenile Mosasaurus may have still utilized shallow waters.

Paleopathology[edit]
M. hoffmannii specimen IRSNB R25, with an infected fracture to the left dentary (seen between the two middle tooth crowns in the back) With its evidently "savage" lifestyle, there are a number of known fossils of M. hoffmannii that exhibit severe physically-inflicted damage. Two specimens from the Royal Belgian Institute of Natural Science cataloged as IRSNB R25 and IRSNB R27 with fractures and other pathologies in their dentary bones have been described by Lingham-Soliar in a 2004 study. The specimen IRSNB R25 preserves a complete fracture near the sixth tooth socket. Extensive amounts of bony callus almost overgrowing the tooth socket are present around the fracture along with various osteolytic cavities, abscess canals, foramina in a trigeminal nerve, and inflamed erosions signifying severe bacterial infection. There are two finely ulcerated scratches on the bone callus, which may have been developed as part of the healing process. Specimen IRSNB R27 has two fractures: one has almost fully healed and the other is an open fracture with nearby teeth broken off, which is likely associated with the dentary fracture. The fracture is covered with a nonunion formation of bony callus with shallow scratch marks and a large pit connected to an abscess canal. Both specimens show signs of deep bacterial infection alongside the fractures; some bacteria may have spread to nearby damaged teeth and caused tooth decay, which may have entered deeper tissue from prior post-traumatic or secondary infections. However, the conditions of the dentaries anterior to the fractures in both specimens are in good condition, indicating that the arteries and trigeminal nerves had not been damaged; if they were, those areas would have necrotized due to a lack of blood. The dentaries' condition suggests that the individuals may have had an efficient process of immobilization of the fracture during healing, which likely helped prevent damage to vital blood vessels and nerves. This, along with signs of healing, also signifies that the fractures were not imminently fatal. The cause of these injuries cannot be determined for certain, but two possibilities exist: One possibility may have been collateral damage from a bite on a hard surface such as a turtle shell, which would have caused intensified stress on the jawbones; another possibility is damage inflicted by another individual during intraspecific combat. The pit in IRSNB R27 has been described as resembling a tooth mark, which gives the possibility that it was the location of an attack by another mosasaur.

In 2006, paleontologists led by Anne Schulp of Utrecht University published a study describing a fossil quadrate of M. hoffmannii with a massive chronic infection. The bone was extensively damaged, had multiple unnatural openings, and an estimated half-liter of bone tissue destroyed. It is likely that this was the result of a severe case of osteomyelitis initiated by septic arthritis, which progressed to the point that a large portion of the quadrate was reduced to voids of abscess. Extensive amounts of bone reparative tissue were also present, suggesting that the infection and subsequent healing process may have progressed for a few months. This level of bone infection would have likely been tremendously painful and severely hampered the mosasaur's ability to use its jaws. The location of the infection may likely have also interfered with respiration. Considering that the individual was able to survive such conditions for an extended period of time, it is likely that it switched to a foraging-type diet subsidizing on soft-bodied prey such as squid that could be swallowed whole to minimize jaw usage. The cause of the infection currently remains speculative, but if it were a result of an intraspecific attack then it is possible that one of the openings on the quadrate may have been the point of entry for an attacker's tooth from which the infection entered.

Avascular necrosis has been reported by many studies to always be present in M. lemonnieri and M. conodon. In examinations of M. conodon fossils from Alabama and New Jersey and M. lemonnieri fossils from Belgium, Rothschild and Martin (2005) observed that between 3-17% of the vertebrae in the mosasaurs' spine were affected by this condition. Avascular necrosis is a common result of decompression illness, caused by bone damage from interference by the formation of gaseous nitrogen bubbles that were produced from inhaled air decompressed during deep or repetitive diving. This indicates that both Mosasaurus species may have either been frequent deep-divers or repetitive divers. Paleontologist Agnete Weinreich Carlsen of the University of Copenhagen commented that it would be frugal to consider the appearance of such conditions being due to non-adaptation in the animal's original state, as fossils of other mosasaurs that also invariably suffer avascular necrosis show evidence of developed eardrums that protected itself from rapid changes in pressure.

Distribution, ecosystem, and ecological impact[edit]
Mosasaurus inhabited the Western Interior Seaway of North America and Mediterranean Tethys of Europe and Africa. Excluding the Pacific species unassessed by Street and Caldwell (2017) and identified as separate genera in Street (2016), Mosasaurus was a transatlantic mosasaur with its fossils having been found in deposits at or nearby both sides of the Atlantic Ocean. These localities include the Midwestern and East Coast of the United States, Canada, Europe, Turkey, Russia, the Levant, the African coastline from Morocco to South Africa, Brazil, Argentina, and Antarctica. During the Late Cretaceous, the aformented regions made up the three seaways inhabited by Mosasaurus: the Atlantic Ocean, Western Interior Seaway, and Mediterranean Tethys. Multiple oceanic climates encompass the seaways including tropical, subtropical, temperature, and subpolar climates. The wide range of oceanic climates yielded a large diversity of fauna that coexisted with Mosasaurus.

Mediterranean Tethys[edit]
The Mediterranean Tethys during the Maastrichtian was located in what is now Europe, Africa, and the Middle East. In recent studies, the confirmation of paleogeographical affinities extends this range to areas across the Atlantic including Brazil and the East Coast state of New Jersey. It is geographically subdivided into two biogeographic provinces that respectively include the northern and southern Tethyan margins. From an ecological view, the two mosasaurs Mosasaurus and Prognathodon appear to be the dominant taxa in the entire seaway, being very widespread and ecologically diversified throughout the Mediterranean Tethys. The northern Tethyan margin was located around the paleolatitudes of 30–40°N, consisting of what is now the European continent, Turkey, and New Jersey. At the time, Europe was a scattering of islands with most of the modern continental landmass being underwater. The northern Tethyan margin provides a warm-temperate climate that was dominated by mosasaurs and sea turtles. M. hoffmannii and Prognathodon sectorius were the dominant species in this province. However, other Mosasaurus species such as M. lemonnieri have been found to be the dominant species in certain areas such as Belgium, where its occurrences greatly outnumber that of other large mosasaurs. Other mosasaurs that have been found in the European side of the northern Tethyan margin include smaller genera such as Halisaurus, Plioplatecarpus, and Platecarpus; the shell-crusher Carinodens; and larger mosasaurs of similar trophic levels including Tylosaurus bernardi and four other species of Prognathodon. Sea turtles such as Allopleurodon hoffmanni and Glyptochelone suickerbuycki also dominated the area and other marine reptiles including undetermined elasmosaurs have been occasionally found. Marine reptile assemblages in the New Jersey region of the province are generally equivalent with those in Europe; mosasaur fauna are quite similar but exclude M. lemonnieri, Carinodens, Tylosaurus, and certain species of Halisaurus and Prognathodon and they exclusively feature M. conodon and some species of Halisaurus and Prognathodon. Many species of sharks such as Squalicorax, Cretalamna, Serratolamna, and sand sharks, as well as bony fish such as Cimolichthys, the saber-toothed herring Enchodus, and the swordfish Protosphyraena are represented in the northern Tethyan margin. Restoration of M. beaugei, which is known from Morocco and Brazil

The southern Tethyan margin was located along the equator between 20°N and 20°S, resulting in warmer tropical climates as typical in the province. Located around what is now Africa, Arabia, the Levant, and Brazil, seabeds bordering the cratons in Africa and Arabia provided vast shallow marine environments. These environments were also dominated by mosasaurs and marine side-necked turtles. Of the mosasaurs, Globidens phosphaticus is the characteristic species of the southern province; in the African and Arabian domain, Halisaurus arambourgi and ’Platecarpus ptychodon’ (a dubious taxon that may represent various mosasaurs such as Gavialimimus or Platecarpus somenensis) were also the dominant mosasaurs. Mosasaurus was not well-represented: the distribution of M. beaugei was restricted to Morocco and Brazil and isolated teeth from Syria suggested a possible presence of M. lemonnieri, although M. hoffmannii has some presence throughout the province. Other mosasaurs from the southern Tethyan margin include the enigmatic Goronyosaurus, the shell-crushers Igdamanosaurus and Carinodens, Eremiasaurus, four other species of Prognathodon, and various other species of Halisaurus. Other marine reptiles such as the marine monitor lizard Pachyvaranus and sea snake Palaeophis are known there. Aside from Zarafasaura in Morocco, plesiosaurs were scarce. As a tropical area, bony fish such as Enchodus and Stratodus and various sharks were common throughout the southern Tethyan margin.

Western Interior Seaway[edit]
Mosasaurus coexisted with bony fish such as Xiphactinus, sea turtles like Protostega and plioplatecarpine mosasaurs in North America.

Many of the earliest fossils of Mosasaurus were found in Campanian deposits in North America, including what was once the Western Interior Seaway, an inland sea that 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 rather shallow for a seaway and had a depth of about 800–900 meters (2,600–3,000 ft) below the surface at its deepest. Extensive drainage from the two neighboring Appalachia and Laramidia continents brought in vast amounts of sediments, and 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, it created a warm and highly-productive seaway that supported a rich diversity of marine life. In fact, many of the most famous marine assemblages of the Late Cretaceous are from deposits in the Western Interior Seaway. However, fossil assemblages throughout these deposits suggest a complete faunal turnover by the time M. missouriensis and M. conodon appeared, and that the presence of Mosasaurus in the Western Interior Seaway had a profound impact on the restructuring of marine ecosystems. The biogeography of the region was generally subdivided into two Interior Subprovinces characterized by different climates and faunal structures, which border around modern-day Kansas. The oceanic climate of the Northern Interior Subprovince was likely a cool temperate one, while the Southern Interior Subprovince had warm temperate to subtropical climates. The faunal structure of both provinces prior to the appearance of Mosasaurus were generally much more diverse, and scientists have classified these periods of diversity as the Niobraran Age. During this age, the Northern Interior Subprovince was dominated by plesiosaurs, hesperornithid seabirds, and the mosasaur genus Platecarpus; and the Southern Interior Subprovince, which was much more diverse than the north in all groups, was dominated by sharks, turtles, and a large diversity of mosasaurs including Tylosaurus and Clidastes.

The appearance of M. missouriensis and M. conodon in the Western Interior Seaway around 79.5 Ma coincided with the transition to the succeeding Navesinkan Age, which coincided with the collapse of the Niobraran order and a complete turnover of marine faunal structure. In what is now modern-day Alabama within the Southern Interior Subprovince, most of the key genera including mosasaurs Clidastes, Tylosaurus, Globidens, Halisaurus, and Platecarpus and sharks such as Cretoxyrhina largely disappeared and were replaced by Mosasaurus. The diversity of marine reptiles as a whole significantly declined and by then Mosasaurus dominated the entirety of the region, accounting for around two-thirds of all mosasaur diversity with Plioplatecarpus and Prognathodon sharing the remaining third. The Northern Interior Subprovince also saw a restructuring of mosasaur assemblages by the beginning of the Navesinkan Age, characterized by the disappearance of mosasaurs like Platecarpus and their replacement by Mosasaurus and Plioplatecarpus. However, Niobraran genera such as Tylosaurus, Cretoxyrhina, hesperornithids, and plesiosaurs including elasmosaurs such as Terminonatator and polycotylids like Dolichorhynchops maintained their presence until around the end of the Campanian, during which the entire Western Interior Seaway started receding from the north. Mosasaurus continued to be the dominant genus in the seaway until the end of the Navesinkan Age during the closure of the Cretaceous. Although the appearance of Mosasaurus in the Western Interior Seaway marked a complete restructuring of marine communities centered around it, there were still a diversity of fauna that coexisted with Mosasaurus. These additional genera included sea turtles such as Protostega and Archelon; many species of sea birds including Baptornis, Ichthyornis, and Halimornis; crocodilians such as Deinosuchus; and many genera of fish including sharks such as Cretalamna, Squalicorax, the goblin shark Scapanorhynchus, Pseudocorax, the sand tiger Odontaspis, Serratolamna, and the saw shark Ischyrhiza; and bony fish such as Enchodus, Protosphyraena, Stratodus, and the ichthyodectids Xiphactinus and Saurodon.

Antarctica[edit]
Mosasaurus fossils were found in the Seymour Island of Antarctica, which once provided cool temperate waters. Mosasaurus is known from Late Maastrichtian deposits in the Antarctic Peninsula, specifically the López de Bertodano Formation in Seymour Island. This locality is estimated to have been located at around ~65°S latitude during the Maastrichtian. Being within the Antarctic polar circle, the Seymour Island locality likely provided a rather unique climate. Chemical studies on oxygen-18 isotopes found in shells and benthic foraminifera have calculated intermediate-depth and deep-sea ocean temperatures at a mean average of 6 °C (43 °F) with fluctuations of up to 4–12 °C (39–54 °F) throughout the Maastrichtian; one of the same studies has also suggested that sea surface temperatures may have been colder, possibly dropping below freezing and forming sea ice at times. Alternatively, a study using the MBT/CBT technique deriving data from cyclization and methylation processes in ancient bacterial membrane lipids yielded a slightly warmer temperature of 12 °C (54 °F) ±5 around 66 Ma. Nevertheless, these estimated climates characterize primarily cool temperate environments with possible intervals of subpolar and warm episodes.

At least two species of Mosasaurus have been described in Seymour Island, but the true number of species is unknown as remains are often fragmentary and specimens are described in open nomenclature. These species include one comparable with M. lemonnieri and another that appears to be closely related to M. hoffmannii. A number of Mosasaurus fossils known in the locality are considered too fragmentary to be identified to the species level. Nevertheless, the genus appears to be the most taxonomically diverse in the Maastrichtian Antarctica. Mosasaurus is not the only mosasaur from Seymour Island; at least four other genera have been reported in similar or same deposits. These include Plioplatecarpus, the mosasaurines Moanasaurus and Liodon, and the tylosaurine Kaikaifilu. However, many of these genera are primarily based on isolated teeth and studies on the dental variability of Kaikaifilu demonstrated the ease of misidentification when examining Antarctic mosasaur teeth. This suggests the possibility that more genera were reported than there actually was. Prognathodon and Globidens are also expected to be present based on distribution trends of both genera, although conclusive fossils have yet to be found. Other marine reptiles included elasmosaurid plesiosaurs such as Aristonectes and another indeterminable elasmosaurid unrelated to the former. The fish assemblage of the López de Bertodano Formation was dominated by Enchodus and ichthyodectiformes, accounting for 21.95% and 45.6% of local fish diversity respectively. Of the remaining percentages, sand sharks made up 10.5%, the cow shark Notidanodon 6.8%, chimaeras 3.9%, saw sharks 2.7%, various other teleost fish 2.4%, and the remaining 6% were shared between other sharks such as Paraorthacodus, frilled sharks, Protosqualus, and Cretalamna.

Habitat preference[edit]
Mosasaurus inhabited offshore ocean habitats of various depths. A traditional method of determining the habitat preference of fossil animals is by determining the habitat represented by the deposits they were from. Known fossils of Mosasaurus have typically been recovered from deposits that represented nearshore habitats during the Cretaceous period, with some fossils coming from deeper water deposits. An early study on the habitat preference by Lingham-Soliar in 1995 elaborated on this, finding that Maastrichtian deposits in the Netherlands with M. hoffmannii occurrences, especially the Maastricht type locality, represented nearshore waters that were around 40–50 metres (130–160 ft) in depth. Changing temperatures and an abundance in marine life were characteristic of these localities. The morphological build of M. hoffmannii, nevertheless, was best adapted for a pelagic surface lifestyle. It had likely resided near the surface and exploited the rich marine assemblages provided by the locality.

A more recently developing approach is through a biogeochemical one, compared to the earlier method of measuring δ13C levels in the enamel of Mosasaurus teeth. Another known correlation with δ13C levels shows that δ13C typically depletes as the foraging habitat of the animal is farther from the shore, meaning that lower levels of the isotope can be correlated with feeding habitation in more open waters and vice versa. This was tested on multiple Mosasaurus fossils in multiple studies which have yielded consistent results signifying that Mosasaurus fed in more offshore or open waters. However, it has been pointed out that measuring δ13C levels may not be the most accurate method of determining the preferred habitat of Mosasaurus. This is because such isotope levels can also be partially determined by other factors in the animal's lifestyle. In M. hoffmannii, one such factor would be its diet while the Bohr effect through diving behavior would have been another possible factor in M. lemonnieri and M. conodon. As a result, isotope levels can misrepresent the actual habitat preferences of Mosasaurus due to such alterations by other factors. As a solution, paleontologists T. Lynn Harrell Jr. and Alberto Perez-Huerta conducted a 2014 study that specifically examined the concentration ratios of neodymium, gadolinium, and ytterbium in M. hoffmannii fossils from Maastrichtian deposits in Alabama, a Mosasaurus specimen from the Campanian-age Demopolis Chalk, and a Mosasaurus fossil from the Hornerstown Formation in New Jersey. Previous studies have demonstrated that ratios in these three elements can act as a proxy for relative ocean depth of a fossil during early diagenesis without interference from biological processes, with each of the three elements signifying either shallow, deep, fresh, or highly saline waters. The rare earth element ratios were found to be very consistent throughout most of the examined Mosasaurus fossils (indicating consistent habitat preference), which were clustered towards a ratio representing offshore habitats with ocean depths between or deeper than 50–150 metres (160–490 ft). A few outliers existed that instead represented shallower waters 50 metres (160 ft) deep or less.