Mosasaurus was a genus of mosasaur from the Late Cretaceous period. Mosasaurus were giant carnivorous, aquatic lizards, somewhat resembling flippered crocodiles, with big elongated jaws.
This genus existed during the Maastrichtian age of the Cretaceous period (Mesozoic era), around 70–66 million years ago in the area of modern Western Europe and North America in a western interior sea and was one of the last mosasaurs. Its name means "Meuse river lizard", as its fragmentary skull was found near the Meuse River in 1764 by lieutenant Jean Baptiste Drouin. It was similar to the North American Tylosaurus, but at 18.5 meters (61 feet) in length, it was even bigger.
It was initially thought to be a species of whale or crocodile considering its large teeth but De Saint-Fond still assumed the specimen represented a crocodile. In 1798 the son of Petrus Camper, Adriaan Gilles Camper, studied the fossil indirectly by reconsidering the description by his father. He was the first to reach the conclusion that the remains were those of a giant monitor lizard, which result in 1799 he corresponded to Georges Cuvier who formally identified it as a completely new but extinct creature (at the time extinct animals were assumed to be like extant animals but giant).
Mosasaurus had unusual skull anatomy which is actually double-hinged like a snake (albeit aquatic and with fins). How it did this is when it was biting down on something large, its jaws would dislocate and unhinge so it would be able to take bigger bites. Its fins were probably used for steering and balance when swimming, not like plesiosaurs who used their fins as their primary means of locomotion. It was very elongated and thin in the body so it was more streamlined so it could move faster for longer periods of time than plesiosaurs who could only accelerate for short periods. Mosasaurus probably had a strong bite force due to eating prey like giant turtles in its time. There are some other species of mosasaur that specialised in eating this kind of prey so they had stronger bites than Mosasaurus who was a generalist predator so it would take anything that fit into its mouth, not unlike tiger sharks today. It is assumed that mosasaurs swam alone since their bite marks have been found on other mosasaurs indicating aggression and territoriality among the species. Mosasaurus more than likely used the same tactics sharks use today to hunt large prey such as plesiosaurs and ichthyosaurs by going down far beneath the prey and getting one devastating surprise attack to avoid injury. To achieve this tactic, It was probably counter shaded so its top was dark to camouflage against the dark ocean below the target and light underneath to camouflage against the sun's bright light. It was also possible that mosasaurus actively chased down its food by using explosive speed and stamina to hunt prey like ichthyosaurs.
It has been recently discovered that the mosasaur genus Platecarpus has a tail fluke on its tail which would aid with swimming. It is not unlikely that other mosasaurs if not all mosasaurs had this tail fluke to achieve even better swimming capability.
Tail muscles gave Mosasaurus the power needed for ambush attacks.
Research history[]
First discoveries[]
TM 7424, the first known specimen of M. hoffmannii
Mosasaurus was the first genus of mosasaur to be named. The first remains known to science were a fragmentary skull from a chalk quarry in the St Pietersberg, a hill near Maastricht, The Netherlands, found in 1764 and collected by lieutenant Jean Baptiste Drouin in 1766. It was in 1790 described as a fish but not named, by Martinus van Marum, the first director of the Teylers Museum at Haarlem.[1] The same year Van Marum procured the fossil for the museum; it is still part of the collection as TM 7424.[2]
At some time between 1770 and 1774 (the often mentioned date of 1780 is incorrect) a second partial skull was discovered and procured by canon Theodorus Joannes Godding, who displayed it in his country house on the slope of the hill. A local retired German/Dutch army physician, Johann Leonard Hoffmann, also collected some fragments and published about the skull; his correspondence with international scientists made the find world famous. Hoffmann presumed the animal was a crocodile. In 1786 however, the Dutch Profesor Petrus Camper disagreed and concluded the remains were those of an unknown sperm whale, of a Physeteris incogniti ex Monte S. Petri.[3]
In 1794 Maastricht, an important fortress city, was captured by the French revolutionary armies. Accompanying the French troops was geologist Barthélemy Faujas de Saint-Fond on a mission to secure the piece, together with représentant du peuple (political commissar) Freicine who during the campaign tried to transport anything of artistic or scientific value he could lay his hands on to France. Finding that it had been removed from the cottage and hidden within the fortress, Freicine offered "six hundred bottles of good wine" to those troops being the first to locate the skull; soon a dozen grenadiers claimed their reward, carrying the piece with them. Early 1795 it was moved to Paris as war booty, by decree declared a national heritage and added to the collection of the new Muséum national d'Histoire naturelle.
MNHN AC 9648, the second skull and holotype of M. hoffmannii, which was nicknamed the "great animal of Maastricht"
Faujas' romantic but inaccurate 1799 interpretation of the second skull's discovery
In 1799 Faujas de Saint-Fond published his Histoire naturelle de la montagne de Saint-Pierre de Maestricht [Tome 2] which also contained an account of the circumstances of the find. According to him Dr Hoffmann paid the quarrymen extra to look out for especially large specimens. When the skull was found on 1770 Hoffmann would have been present during the excavation. Afterwards Godding would have claimed his rights as landowner and forced Hoffmann to relinquish his ownership through a lawsuit, won by influencing the court. De Saint-Fond would nevertheless in 1795, saving the specimen for science, have paid a considerable indemnity to Godding to compensate for his loss. However, as Dutch historian Peggy Rompen showed, of this famous story very little can be substantiated by other sources. Godding was the original owner, Hoffmann clearly never possessed the fossil, there was no lawsuit, de Saint-Fond probably never paid anything and the entire account seems to have been fabricated by him to justify the dispossession by military force.[4]
De Saint-Fond still assumed the specimen represented a crocodile. In 1798 the son of Petrus Camper, Adriaan Gilles Camper, again studied the fossil indirectly by reconsidering the description by his father. He was the first to reach the conclusion that the remains were those of a giant monitor, which result in 1799 he corresponded to Georges Cuvier.[5]
In 1808 Cuvier confirmed Camper's result. The fossil had already become part of Cuvier's first speculations on the possibility of animal species going extinct. The idea of extinction paved the way for his theory of catastrophism or "consecutive creations", one of the predecessors of the evolution theory.
A scientific name had not yet been given to the new species, the specimen usually being referred to as the Grand Animal fossile des Carrières de Maëstricht or "Great Fossil Animal of the Maastricht quarries". In 1822 William Daniel Conybeare named it Mosasaurus after the Latin name (Mosa) of the Maas (Meuse) River passing through Maastricht, the second skull being the holotype, MNHNP AC9648. The specific name (epithet) hoffmannii was added by G.A. Mantell in 1829, honouring surgeon C.K. Hoffmann, on the presumption he was the discoverer of the type specimen. Today the emendated form hoffmanni is most often used.
In 1854 German biologist Hermann Schlegel was the first to conjecture Mosasaurus had flippers instead of normal feet.
In 1998, another, even bigger and more intact fossil skull was found in the Maastricht limestone quarries, nicknamed "Bèr", and displayed in the Maastricht Natural History Museum. However, it was determined this find represented a new species of the genus Prognathodon.
M. missouriensis holotype, with the Harlan snout (MNHN 9587) attached to the Goldfuss skull (RFWUIP 1327); drawn in 1834 and 1845 respectively
The Lewis and Clark Expedition (1804) discovered a (now-lost) specimen from the Missouri River, then identified as a 45-foot (14-meter)-long fish. Richard Ellis (2003) speculates his may have been the first M. missouriensis discovered, but competing specimens have been recalled. In 1818, a specimen from Monmouth County, New Jersey became the first North American specimens to be referred to Mosasaurus. Richard Harlan (1834) described the type M. missouriensis from a rostral fragment discovered around the river's Big Bend, assigning it as Ichthyosaurus, and later, an amphibian. The remaining skull was found earlier by a fur trapper, with prince Maximilian of Weid-Neuwied (between 1832 and 1834) obtaining it. It was then delivered to Georg August Goldfuss, who published about it in 1845. The same year, Christain Erich Hermann von Meyer speculated that it and Harlan's skull were the same individual. This was confirmed in 2004. Edward Drinker Cope (1881) named M. conodon from fragments in New Jersey as a giant species of Clidastes, later reassigned to Mosasaurus in 1966. M. lemonnieri was found by Camper Jr. from fossils of his father's collections, discussed with Cuvier in a 1799 correspondence. However, Cuvier rejected the concept of Mosasaurus as non-monotypic. Louis Dollo (1889) reintroduced and named the species based on a skull from a Belgium phosphate quarry. Further excavation in said quarry recovered more well-preserved remains, including multiple partial postcrania, which represented a near-complete skeleton. Dollo described these later. Being the best anatomically-represented, M. lemonnieri was ignored in publications, for which Theagarten Lingham-Soliar suggested two reasons. First, it attracted little paleontologists, and second, it was overshadowed by the legendary type species.
M. lemonnieri is a controversial species, and it is debated if it is valid. Dale Russell (1967) argued it an M. conodon are the same, setting the former as a junior synonym of the latter. Lingham-Soliar (2000) refuted this based on comprehensive study of specimens, which is corroborated by an M. conodon cranial study by Ikejiri and Lucas (2014). Eric, Mulder, Dirk Cornelissen and Louis Verding (2004) suggested M. lemonnieri could be a juvenile M. hoffmannii, based on the argument that differences are age-based. However, more research is required[6]. M. beaugei was named by Camille Arambourg (1952) based on isolated teeth from the phosphate deposits of the Oulad Abdoun Basin and Ganntour Basin. Mosasaurine remains excavated from Breien Member, Hell Creek Formation in 2016 were found to belong to an indeterminate mosasaurine by Clint Boyd and Nathan Van Vranken (2021), which is either assignable to M. hoffmannii or Prognathodon. This proves that large mosasaurs lived with Hell Creek fauna. These remains represent an individual 15 meters long. This was a coastal taxon, who may have ventured into more brackish water. The specimen was collected from the property of a landowner, who had found loose at the base of a hill, and a vertebrae was sent to Clint Boyd to analyze. Shrimp burrows nearby indicates the remains were possibly scattered as they pushed tissue out of their way, with small shark teeth also found nearby. More remains were found emerging from prairie grass, whose roots had extended so deep it was difficult to prepare them. They were brought back to a lab to further prepare[7].
One specimen, postcrania, were collected from 2012 through 2014 and the second specimen, a skull and neck, were collected from Pembina Gorge in 2015-2016. These specimens were discovered 2 meters apart, directly atop each other. The hillside quarry they were recovered from slopes down toward a passing road, and it is thought that the postcrania were separated from the crania were dislodged from one another and were sent in different directions, rather than two individuals. This is further evidenced by how no overlapping material is present, the parts are "almost perfectly complimentary" and how the material has consistent size. Clint Boyd is working on describing it. It may be part of the Pierre Shale[8][9][10]. It is similar to M. conodon and may represent variation in this species or something novel[11].
Paleoart[]
An 1854 depiction of Mosasaurus in Crystal Palace Park
Mid-1800s depictions of Mosasaurus typically consists of an amphibious marine reptile that has webbed feet for walking. This was based on the M. missouriensis holotype, which had an elastic vertebral column that Goldfuss (1845) saw as evidence for walking, alongside analyses of phalanges. Hermann Schlegel (1854) saw Mosasaurus had fully aquatic flippers by showing the "claws" were erroneous and the phalanges showed no signs of muscle/tendon attachment. They were also flat, broad and formed a paddle-like shape. This was largely ignored by scientists at the time, but was accepted in the 1870s when Othniel Charles Marsh and Cope found more complete remains in North America. Some of the earliest paleoart is a life-sized concrete sculpture made by Benjamin Water house Hawkins (between 1852 and 1854) as part of the Crystal Palace statues. It was partially-informed by Richard Owen's interpretation of the holotype and monitor lizards, depicting it as an aquatic version of the latter with a boxy head, nostrils oriented to the side, large amounts of tissues around the eyes, lips, flippers and monitor-esque scales. It was deliberately sculpted incomplete, stated by Mark Witton later, to likely save time and money. Even back then, many elements could be considered inaccurate, as it neglected Goldfuss (1845)'s research, which called for a narrower skull, nostrils oriented at the top of the skull and terrestrial limbs (now seen as inaccurate)[6].
Description[]
Life restoration of M. hoffmannii, one of the largest known mosasaurs[12]
Mosasaurus was a type of derived mosasaur, a latecoming member that has evolved advanced traits such as a fully aquatic lifestyle. As such, Mosasaurus had a streamlined body, elongated tail that ended with a hypocercal downturn that supported a two-lobed fin, and two pairs of flippers. While in the past derived mosasaurs were depicted as akin to giant flippered sea snakes, it is now understood that they were more similar in build to other large marine vertebrates such as ichthyosaurs, marine crocodylomorphs, and archaeocete whales through convergent evolution.
In 2022, the presence of M. hoffmannii in the Moroccan Maastrichtian Phosphates from a marginal tooth crown was published[6]. A Mosasaurus sp. tooth was recovered from the Peedee Formation on a grand stand beach[13].
M. hoffmannii has a blunt snout and M. lemmonieri has a pointed snout. The foramina in the jaws are similar in pattern to Clidastes. All species except M. conodon have skulls that are robust, broad and deep. M. hoffmannii and the largest specimens of M. lemmonieri have a slightly upturned dentary. However, more typical skulls of the former are straighter. In M. hoffmannii and M. lemmonieri, the premaxillary bar constricts near the midpoint, typical of mosasaurs, but M. missouriensis has a robust bar that does not constrict. In M. hoffmannii, the external nares are 21-24% of the skull length, and placed farther back than any other mosasaur except Goronyosaurus, beginning above the 4th and 5th maxillary teeth. Thus, the posterior of the maxilla lack a dorsal concavity, which would fit the typical mosasaur nostril. The palate is compacted for stability, the brain was more slender and smaller than other mosasaurs, the occipital lobe and cerebral hemisphere are narrow and shallow, suggesting they were small, the parietal foramen is the smallest in any mosasaurid and the quadrate is tall and somewhat rectangular.
Cutting structures, prismatic surfaces and two opposite cutting edges diagnose the genus. M. conodon and M. lemmonieri are the only species whose teeth are not large and robust. M. hoffmanni and M. missouriensis have finely serrated edges while M. conodon and M. lemmonieri do not have serrations and M. beaugei has edges that are nor serrated nor smoothed, with small crenulations. The number of prisms in the teeth vary between tooth types and between species; M. hoffmannii has 2-3 on the labial side and none on the lingual, M. missouriensis has 4-6 on the labial and 8 on the lingual, M. lemonnieri has 8-10 on the labial and M. beaugei has 3-5 on the labial and 8-9 on the lingual. Mosasaurus has 2 premaxillary, 12-16 maxillary, 8-16 pterygoid and 17 dentary teeth, which were homodont, minus the smaller pterygoid teeth, This makes 20-34 teeth on the upper jaw and 17 on the lower, on average, since the number of teeth on each region varies between species and individuals. M. hoffmannii has 14-16 maxillary, 14-15 dentary and 8 pterygoid teeth. M. missouriensis has 14-15 maxillary, 14-15 dentary and 8-9 pterygoid teeth. M. conodon has 14-15 maxillary, 16-17 dentary and 8 pterygoid teeth. M. lemmonieri has 15 maxillary, 14-17 dentary and 11-12 pterygoid teeth. M. beaugei has 12-13 maxillary, 14-16 dentary and 6 (or more) pterygoid teeth. An indeterminate specimen of Mosasaurus and similar to M. conodon from Pembina Gorge State Recreation Area, North Dakota has 16 pterygoid teeth, which is much larger than any species. The dentition was thecodont and constantly replacing, finding 10.9 micrometers of odontoblasts per day in M. hoffmannii. This was found through the von Ebner lines, which further finds it took 511 days for the odontoblasts and 233 days for the dentin to develop the teeth.
M. sp. SDSM 452 is one of the most complete specimen in terms of vertebrae, having, 7 cervicals, 38 dorsals, 8 pygal and 68 caudals. All species have 7 caudals, but other counts vary; Partial skeletons of M. conodon, M. hoffmannii and M. missouriensis suggest that M. conodon probably had up to 36 dorsals and 9 pygals. M. hoffmannii has up to 32 dorsals and 10 pygals, M. lemmonieri with ~40 dorsals, 22 pygals and 90 caudals (the most vertebrae-rich of the genus) and M. missouriensis with ~33 dorsals, 11 pygals and at least 79 caudals. The ribs were very deep and makes an almost perfect semicircle in cross-section, which makes the chest barrel-shaped. Cartilage attached the ribs rather than bone fusion, which aided with breathing in deep water. Bone texture is nearly identical to cetaceans, which suggests neutral buoyancy and aquatic adaptation. The tail is similar to Proganthodon and evidence for two lobes is present. The caudals gradually shorten at the center of the tail and lengthen behind the center, which made the tail rigid around the center and flexible behind that point. The dorsal plane slightly offsets the tail bend that starts at the midpoint. The large haemal arches bend at the tail's midpoint. All of these suggest the fluke at the end of the tail was a power locomotion device. The fins were wide anf robust, the scapula and humerus are fan-shaped and wider than the tail, the radius and ulna were short (the former taller than the latter), the ilium is slender and rod-like (being ~1.5x longer than the femur in M. missouriensis), the femur is 2x as long than its width and ends at the distal side in a pair of articular facets that meet at an angle of ~120°, the 5th set of metacarpals and phalanges shorter and offset, compressed paddle structure similar to Plotosaurus (suggesting fast swimming) and hindlimbs that have 4 digits[6].
Size[]
Size range of Mosasaurus compared with a human
| Author | Species | Length | Method | References |
|---|---|---|---|---|
| Russell (1967) | M. hoffmannii | "jaw equalled one tenth of the body length in the species." | Educated guess. | [6] |
| Grigoriev (2014) | 17.1 meters (56 feet) | By using Russel (1967)'s estimation and the largest mandible, CCMGE 10/2469 (171 centimeters long), to find this length. | ||
| Lingham-Soliar (1995) | 17.6 meters (58 feet) | By using the small mandible NHMM 0090002 (preserving 90 centimeters) which was "reliably estimated" to be 160 centimeters long. | ||
| Federico Fanti et al. (2014) | "closer to seven times the length of the skull" (144cm skull=11m individual?) | Based on a well-preserved specimen of Prognathodon overtoni. | ||
| Everhart et al. (2016) | 18 meters (59 feet) | From an unknown head/body ratio; based on quadrate NHMM 003892, which is 150% larger than the average. | ||
| Dollo (1892) | M. lemmonieri | 7-10 meters (23-33 feet) | Based on various Belgian skeletons and IRSNB 3119, making a head/body ratio of 1:11. | |
| Polcyn et al. (2014) | M. missouriensis | 8-9 meters (26-30 feet) | ||
| Street (2016) | Finding skulls that typically exceed over 1 meter. | |||
| Gramling (2016) | A specimen reportedly 6.5 meters long with a skull of about 1 meter. | A near-complete specimen. | ||
| Nathalie Bardet (2015) | M. beaugei | 8-10 meters (26-33 feet) | Based on pers. obs. undescribed Moroccan occurrences. Found the skull to be a meter long. | |
| Ikejiri and Lucas (2014) | M. conodon | Found the skull to be 97.7 centimeters long, making it small to medium-sized. No total size extrapolations are found in literature. |
Classification[]
History of taxonomy[]
Fossil skull of the proposed new species M. glycys{
Because the rules of nomenclature were not well defined at the time, 19th century scientists did not give Mosasaurus a proper diagnosis during its first descriptions. This led to ambiguity regarding the definition of the genus, which led it to become a wastebasket taxon that contained as many as fifty different species. The taxonomic issue was so severe that there were cases of species that were found to be junior synonyms of species that were found to be junior synonyms themselves. For example, four taxa became junior synonyms of M. maximus, which itself became a junior synonym of M. hoffmannii. This issue was recognized by many scientists at the time, but efforts to clean up the taxonomy of Mosasaurus were hindered due to a lack of a clear diagnosis.
Phylogeny and evolution of the genus[]
Russell (1967) was one of the earliest evolutionary attempts at defining Mosasaurus, finding a Clidastes-like ancestor that diverged into two lineages, one leading to M. conodon and the other having several chronospecies (M. ivoensis, M. missouriensis and M. maximus-hoffmannii (in that order)). However, he used an early version of phylogenetics rather than cladistics. Bell (1997) published a cladistic analysis of North American mosasaurs, finding M. missouriensis, M. conodon, M. maximus and USM 77040, an indeterminate specimen, finding some agreements with Russell (such as ancestry related to Clidastes and M. conodon being the most basal). Contrary, he found a sister relationship with Globidens and Prognathodon, with M. maximus sister to Plotosaurus. This made the genus paraphyletic, but Plotosaurus was still determined valid by Bell. This study formed a precedent for later works, although some later studies replace the sister clade of Mosasaurus/Plotosaurus to consist of Eremiasaurus and Plesiotylosaurus depending on the methodology, and at least one study finding M. missouriensis to be the most basal of the genus. Konishi et al. (2014) expressed concerns with Bell, finding that the sample severely underrepresented the genus, leaving a wealth of material unaccounted for and thus distorting phylogeny. They also find that the holotype data was unclear and made the taxonomy shaky and that there was a lack of comparative anatomical studies. Street (2016) used this to update their results. Conrad (2008) used only M. hoffmannii and M. lemmonieri, finding the former to be basal to many descendants, from most to least basal, Globidens, M. lemmonieri, Goronyosaurus and Plotosaurus. This suggests that they are not the same genus, but this was unorthodox because he focused on squamates and not mosasaurs specifically. This had led to many disregarding this result based on technical issues[6].
Evolution[]
As with most mosasaurs, their legs and feet are modified into hydrofoil-like flippers, with the forelimbs larger than the hindlimbs. The first mosasaur ever discovered, Mosasaurus hoffmannii, was excavated in a mine near Maastricht, the Netherlands in the 1770s. Like its American relatives Tylosaurus and Hainosaurus, Mosasaurus reached lengths of about 15 meters. However, Mosasaurus was much more robust than tylosaurine mosasaurs, at some double the weight of a mosasaur of the same length. In life, a 10 m long Mosasaurus was as heavy as a 15 m long Tylosaurus.
Anatomy[]
Mosasaurus was among the last mosasaur genera, and among the largest. The skull was more robustly built than other mosasaurs, as the mandibles articulated very tightly with the skull. It had a deep, barrel-shaped body, and with its fairly large eyes, poor binocular vision, and poorly developed olfactory bulbs, experts believe that Mosasaurus lived near the ocean surface, where it preyed on fish, turtles, ammonites, and possibly smaller mosasaurs. The animal remained near the surface and although it was able to dive, it most likely did not venture into deeper waters.
The skull of Mosasaurus tapered off into a short, conical process, and the jaws were armed with massive, sharp, conical teeth. Their paddle-like limbs had five digits in front and four in back. The trunk terminated in a strong tail which, together with serpentine undulation of the whole body, contributed far more to the animal's locomotion that did the limbs.
Because of its robust skull and tightly articulating jaws, Mosasaurus was unable to swallow prey-items whole in the manner of earlier mosasaurs, such as Tylosaurus. Instead, with the aid of its curved, knife-like teeth, Mosasaurus was able to tear its prey into more manageable pieces that could be more easily swallowed.
As mentioned before, Mosasaurus was discovered near the town of Maastricht, located at the southernmost tip of the Netherlands. The city is largely built with blocks of limestone from the town's quarry. In 1770, the local Dutch army physician, Dr Hoffmann, who had developed an interest in the strange bones that kept showing up in these blocks of limestone, paid the quarrymen extra to look out for especially large specimens. The best of these was found in 1774, and it was named Mosasaurus hoffmannii. It was a very controversial find, as the skull belonged clearly to a species that no longer existed on earth, and it raised the first speculations on the possibility of animal species going extinct. The idea of extinction paved the way for the theory of "several creations", one of the predecessors of the evolution theory. A few years after the find, the French armies occupied Maastricht and the fossil skull was taken to Paris, where it is was studied by G. Cuvier. The skull still on display in the Muséum National d'Histoire Naturelle.
In 1998, another, even bigger and more intact fossil Mosasaurus skull was found in the Maastricht limestone quarries. It was nicknamed "Ber" and it is currently on display in the Maastricht Natural History Museum.
Relatives[]
The family Mosasauridae is split into several subfamilies, with Mosasaurus being placed within Mosasaurinae. This subfamily, in turn, is further split into smaller tribes, with Mosasaurus being grouped with Clidastes, Moanasaurus, Amphekepubis, and Liodon in the tribe Mosasaurini.
Paleobiology[]
Head musculature and mechanics[]
The skull of M. hoffmannii was adapted to withstand powerful bites.
Much of the knowledge on the musculature and mechanics of the head of Mosasaurus are largely based on Lingham-Soliar's 1995 study on M. hoffmannii skulls. Because soft tissue like muscles do not easily fossilize, reconstruction of the head musculature is largely based on the structure of the skull, the nature of muscle scarring on the skull, and the musculature in extant monitor lizards.
Life History[]
Reconstruction of an M. hoffmannii forelimb
Mosasaurus used sub-carangiform tail-based swimming, using their flippers as hydrofoils. Large muscles attached to the o name="1:"utwards-facing surface of the humerus to the radius, ulna and then modified joints that enhanced flipper rotatation. The powerful force generated by using these may have sometimes caused boen damage, based on an M. hoffmannii ilium with the head significantly separated from the body caused by shearing forces in the articulation joint. The tissue structure in the bones suggests a metabolic rate that is much higher than modern squamates and a resting metabolism between a leatherback turtle and ichthyosaurs/plesiosaurs. It was likely endothermic and had a constant, distinct body temperature. Clidastes indicates that endothermy was present in all mosasaurs. This is unique to squamaes, except for several species, which would have allowed Mosasaurus to have increased stamina when foraging in larger areas and pursuing prey (among other things). It may have allowed some species of this genus to live in colder climates such as Antarctica. It was likely viviparous, but there is no direct evidence of live birth in Mosasaurus though it is inferred from other taxa. Microanatomical research on juvenile elements suggest that juveniles had bone structures comparable to adults, unlike older mosasauroids who bear different structure to support buoyancy in shallower water. This implies that they were percocial, being fully functional in open water at very young age and did not require nurseries. However, some European and South Dakotan assemblages of concentrated juvenile M. hoffmannii, M. missouriensis and M. lemmonieri suggest that some juveniles lived in shallow waters[6].
Senses[]
Sclerotic ring of Mosasaurus
It had large orbits and large sclerotic rings that occupied much of the orbit's diameter, with corresponds with a large eye size and good vision. The binocular field was small, ~28.5°, based on the placement of the eyes at the sides of the skull. This would have allowed for excellent processing of 2D environments, such as the near-surfce environments they lived in. Brain casts made from Mosasaurus suggest that the olfactory bulb and vomeronasal organ, both controlling smell, were poorly developed and lack some structures in M. hoffmannii. This suggests a poor sense of smell. In M. lemmonieri, these are still small but are better developed and have the parts lacking in derived forms. This suggests that olfaction was not very important in Mosasaurus, exploiting other senses[6].
Diet[]
Restoration of M. hoffmannii preying on a sea turtle
Mosasaurus was likely an active predator that fed on bony fish, sharks, cephalopods, birds and marine reptiles, including other mosasaurs and turtles. It is unlikely to be a scavenger based on the poor sense of smell. It's great size, heavy bite and robust teeth would have allowed it to challenge any animal. Lingham-Soliar (1995) suggested a "savage" feeding method based on large tooth marks on the scutes of Allopleuron hofmanni and rehealed jaw fractures in M. hoffmannii. It likely hunted near the surface, as its eyes were better suited to this environment, ad an ambush predator. M. lemonnieri and M. conodon may have hunted in deeper water based on chemical and structural data. Carbon isotope of M. hoffmannii suggests that they had the lowest value of δ13C of the largest mosasaur individuals. Mosasaurs with a higher value occupied higher trophic levels and those with lower were caused by a prey diet rich in sea turtles, large marine reptiles and other lipids. This suggests that M. hoffmannii was an apex predator. A small M. missouriensis of 75 million years old is one of the few examples of stomach contents preserved in mosasaurs. It is a partial skeleton with dismembered and punctured remains of a 1-meter-long fish in its gut. Though it is much longer than its entire skull, it dismembered prey and consumed parts. It lived with Prognathodon, who focused on robust prey, so by niche partitioning it preyed on animals that were best consumed via cutting-adapted teeth. Mosasaurus may have taught children how to hunt, as seen in a specimen of Argonautilus catarinae that preserves bite marks from 2 conspecific mosasaurs, one a juvenile and the other an adult. Kauffman (2014) suggests that they were made either by Mosasaurus or Platecarpus, with the nautiloid either sick or dead upon attack given the direction of the marks. This is either the parent teaching of alternate food sources, or a juvenile weakly biting once and then strongly biting. However, the spacing suggests different jaw sizes[6].
Conflict[]
M. missouriensis skull with another individual's tooth embedded in the rear lower jaw, likely via head grappling
Intraspecific combat was aggressive and lethal. One partial M. conodon bears multiple cuts, breaks and punctures across the skeleton, particularly on the rear skull and neck, and a tooth of the same species penetrating the quadrate. None of these show evidence of healing, suggesting that a fatal blow to the skull killed it. An M. missouriensis skeleton has a tooth from another individual lodged in the lower jaw under the eye, where healing was detected and implying survival. Konishi ssuggests that this head biting may have occurred in courtship. Some injuries attributed to intraspecific combat may actually be due to attempting to crush turtle shells. Lingham-Soliar (2004) suggests that if they were intraspecific, then a pattern of head-specific injury would be observed. Modern crocodiles attack other individuals by grappling their heads with their jaws, with Lingham-Soliar suggesting that Mosasaurus did this. Many of these specimens with injuries are juveniles or subadults, so it may have been common to attack them due to being smaller or weaker. However, the attackers in M. conodon and M. missouriensis were likely of similar size to their victims. Schulp et al. (2006) speculated that these encounters may have occasionally led to cannibalism[6].
Paleopathology[]
M. hoffmannii specimen IRSNB R25, with an infected fracture to the left dentary (seen between the two middle tooth crowns in the back)
IRSNB R25 and IRSNB R27, M. hoffmannii, both bear fractures and other pathological elements on their dentaries; the former has a full fracture near the 6th tooth, with extensive bony callus overgrowing the socket and along various osteolytic cavities, abscess canals, trigeminal nerve damage and inflamed erosions that suggest severe bactarial infection are seen. Two finely ulcerated marks on the bone callus may have developed during healing. In the latter, one fracture with full healing and an open one with broken teeth as a result. It it is covered by a nonunion formation of callus with shallow scratching and a large pit that connects to the abscess canal. Lingham-Soliar thought this pit resembled tooth marks from an attacking mosasaur. Both specimens had deep bacterial infection and fracturing, which suggests that bacteria may have travelled to damaged teeth nearby and caused tooth decay, which in turn may have penetrated to deeper tissue from prior post traumatic or secondary infections. The dentaries ahead from the fractures are of good condition, which suggests effective fracture immobilization during healing, preventing further damage to vital blood vessels and nerves, which suggests that they were not fatal. Schulp et al. (2006) describe a quadrate of the same species with multiple openings with an estimated 0.5 liters (0.13 US gallons) of tissue lost, likely a severe bone infection initiated by septic arthritis and spread to a large area of the quadrate and reduced said part to abscess. Much reparative bone tissue suggests the infection and healing may have spanned several months of painful recovery. This would have hampered its biting ability and possibly even breathing. They speculated that it may have had to forage on soft-bodied prey such as squid that could be consumed whole based on this. One of the marks may have been a tooth puncture that became infected if this is intraspecific, though it is unknown. Avascular necrosis have been found in every specimen of M. lemmonieri and M. conodon in Alabama/New Jersey and Belgium, respectively. Rothschild and Martin (2005) found it affected 3-17% of mosasaur vertebrae. This is often caused by decompression sickness, which suggests that these animals were habitual deep divers or repetitive divers. Carlsen considered the simplest explanation was that they were inadequately adapted. However, mosasaurs who suffered decompression sickness still show substantial adaptation in the eardrum (against rapid pressure shifts). Unnatural caudal fusion is found in this genus, which occurs during remodeling after trauma or disease. Rothschild and Everhart (2015) compiled 15 specimens from North America and Belgium and found fused caudals in 3. 2 of such had irregular surface deformities around the fusion site that was caused by vertebral sinus drainage and thus bone infection. The cause of this infection is uncertain, but fused vertebrae in other mosasaurs is typically indicative of shark attacks and other predation attempts. The third case was caused by a form of arthritis based on how the bridging bone tissue is smooth[6].
Paleoecology[]
Distribution, ecosystem, and ecological impact[]
Mosasaurus inhabited the Western Interior Seaway of North America and Mediterranean Tethys of Europe and Africa.
It was a transatlantic species found on both sides of the Atlantic, including the Midwest and East Coast of the United States, Canada, Europe, Turkey, Russia, the Levant, Morocco to South Africa, Brazil, Argentina and possibly Antarctica. These comprise the Atlantic Ocean, Western Interior Seaway and Mediterranean Tethys during the Cretaceous, spanning tropical, subtropical, temperate and subpolar climates. The Mediterranean Tethys was located in Eurasia and Africa during the Maastrichtian, with most of today's landmass being submerged. M. hoffmannii and Prognathodon sectorius were dominant in the north. In Belgium, M. lemmonieri was far more dominant. Other mosasaurs in the European sector include Halisaurus, Plioplatecarpus, Platecarpus, Carinodens, Tylosaurus bernardi and Prognathodon sensu lato. Other taxa include Allopleurodon, Glyptochelone and elasmosaurs. In New Jersey, the fauna is similar but lacks M. lemmonieri, Carinodens. Tylosaurus and certain Halisaurus and Prognathodon species. M. conodon, Halisaurus platyspondylus and Prognathodon rapax are here exclusive. Fish fauna in the northern Tethyan margin include Squalicorax, Cretalamna, sand sharks, Cimolichthys and other bony fish, Enchodus and Protosphyraena. The southern margin, along the equator and thus more tropical, extended through Africa, Arabia, the Levant and Brazil providing many shallow environments. Here, Globidens phosphaticus is characteristic, with the African and Arabian sector dominated by Halisaurus arambourgi and Gavialimimus and were contemporaneous with Globidens. M. beaugei distribution here is restricted to Morocco and Brazil, with M. lemmonieri possibly in Syria and M. hoffmannii having some presence. Other mosasaurs include Goronyosaurus, Igdamanosaurus, Eremiasaurus, Prognathodon, Halisaurus and Carinodens. Other fauna are Pachyvaranus. Palaeophis, Zarafasaura, plesiosaurs, Enchodus, Stratodus and sharks.
Western Interior Seaway[]
Mosasaurus coexisted with bony fish such as Xiphactinus, sea turtles like Protostega and plioplatecarpine mosasaurs in North America.
Many of the earliest Mosasaurus discoveries were from the Western Interior Seaway, which once flowed through central United States and Canada, connecting the Arctic Ocean to the Gulf of Mexico, being shallow for a seaway. A full faunal turnover when M. missouriensis and M. conodon appear 79.5 million years ago suggests that this genus has a lasting effect in this area. This faunal assemblage is generally more diverse than other bodies of water before Mosasaurus appears during the Niobraran Age. The assemblage includes Clidastes, Tylosaurus, Globidens, Halisaurus and Platecarpus as key species that vanished upon Mosasaurus colonization. However, taxa such as Tylosaurus, Cretoxyrhina (another key species), hesperornithids, Terminotator and Dolichorhynchops persist until the uppermost Campanoan, which the seaway began to recede northwards. Other taxa include Protostega. Archelon, Baptornis, Ichthyornis, Halimornis, Cretalamna, Squalicorax, Pseudocorax, Serratolamna, Scapanorhynchus, Odontaspis Ischyrhiza. Enchodus, Protosphyraena, Stratodus, Xiphactinus and Saurodon. It was one of the most dominant faunal elements in the Western Interior Seaway until the rear of the Navesinkan Age near the terminal Cretaceous.
Interspecific competition[]
Mosasaurus was able to coexist with other large predatory mosasaurs like Prognathodon through niche partitioning.
It was a large apex predator that was a contemporary of tylosaurines and Prognathodon sensu lato, and all survived on similar prey items. Schulp et al. (2013) tested P. saturator and M. hoffmannii using δ13C analysis to find the degree of contemporeity. Though similar, the results show that their levels differed in the Maastricht Formation and there was some convergence and niche partitioning through different foraging areas and diets. The teeth of M. hoffmannii are somewhat adapted for turtles, but better towards a wide range of prey; whereas the other was specialized to robust prey like turtles. Konishi et al. (2014) report similar niche partitioning through dietary divide in the Bearpaw Formation, M. hoffmannii and "P." overtoni, in preserved stomach contents. The latter preserves turtles and ammonites, robust prey, and the former with fish, softer prey. However, evidence of interspecific combat amongst species suggests that competition did take place. One subadult M. hoffmannii with fractures caused by one large blow to the neurocranium was argued by Lingham-Soliar (1998) to have been from a ramming attack by Tylosaurus bernardi; the pathology bears traits similar to concentrated blows and such lines up with its robust yet angular, elongate snout. This is seen in bottlenose dolphins when warding away/killing lemon sharks: therefore, this Tylosaurus may have ambushed the M. hoffmannii[6].
Extinction[]
By the end of the Cretaceous, mosasaurs like Mosasaurus were at a height of evolutionary radiation, and their extinction was a sudden event.
Appearance in other media[]
Jurassic Park[]
- A Mosasaurus was featured prominently in Jurassic World, the fourth film in the Jurassic Park series. According to the park staff, the Mosasaurus is a female. It is shown breaching on water to consume a great white shark hanging above the surface. It lives in a 3,000,000 gallon pool in Jurassic World Lagoon during the feeding show. The visitors are also taken to an underwater viewing station to have a closer look at the Mosasaurus.
- Mosasaurus has a few scene appearances in this installment. It is later seen eating one of the Pteranodons that escaped the aviary when the Isla Nublar incident occurs. It is last seen pulling the Indominus rex (a fictional hybrid dinosaur) under the water during the final battle with Rexy the Tyrannosaurus rex and Blue the Velociraptor and saving the park.
- Mosasaurus was confirmed for Jurassic World: Fallen Kingdom by Chris Pratt and Bryce Dallas Howard. The individual Mosasaurus seen in Jurassic World has survived the years it has spent on Isla Nublar, although it, alongside many other creatures, will now face an impending danger in the form of an erupting volcano. The Mosasaurus has been confirmed on the Jurassic World website to have escaped into the ocean. She was last seen in the open ocean attacking surfers.
- In Jurassic Park: Builder, Mosasaurus can be created in the aquatic section of the park as a limited edition "dinosaur".
- In Jurassic World: The Game, Mosasaurus is a legendary surface sea reptile. At first, it could only be seen swimming in the Jurassic World Lagoon without the player being able interact with it, create it, or use it in the battle arena. This was until September 30, 2015 when the Mosasaurus appeared. Since then, the shadow in the lagoon has disappeared until you get the mosasaur. It was only available in either winning it in the Mosasaurus tournament or win it by spinning the tournament wheel and landing on it, but it now can be obtained by either purchasing an Aquatic Card Pack, or winning an Aquatic Card Pack that contains it from the arena.
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References[]
- Bardet, N. and Jagt, J.W.M. 1996. Mosasaurus hoffmanni, le “Grand Animal fossile des Carrières de Maestricht”: deux siècles d’histoire. Bulletin du Muséum national d’Histoire naturelle Paris (4) 18 (C4): 569–593.
- Benes, Josef. Prehistoric Animals and Plants. Pg. 144. Artia, 1979
- Mulder, E.W.A. 1999. Transatlantic latest Cretaceous mosasaurs (Reptilia, Lacertilia) from the Maastrichtian type area and New Jersey. Geologie en Mijnbouw 78: 281–300.
- ↑ M. van Marum, ‘Beschrijving der beenderen van den kop van eenen visch,…’, Verhandelingen Teylers Tweede Genootschap 9 (1790), p. 383-389
- ↑ Mulder, Eric Wolfgang Amadeus. 2004. "Maastricht Cretaceous finds and Dutch pioneers in vertebrate palaeontology". In: Touret, J.L.R. & Visser, R.P.W. (eds). Dutch pioneers of the earth sciences, pp. 165-176. Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam
- ↑ P. Camper, "Conjectures relative to the petrifactions found in St. Peter’s Mountain near Maestricht", Philosophical Transactions, 76: 443-456
- ↑ P. Rompen, 1995, Mosasaurus hoffmanni: De lotgevallen van een type-exemplaar
- ↑ A.G. Camper, 1800, "Lettre de A.G. Camper à G. Cuvier sur les ossemens fossiles de la montagne de St. Pierre, à Maëstricht", Journal de Physique 51 (1800) p. 278-291
- ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 https://en.wikipedia.org/wiki/Mosasaurus
- ↑
- ↑ https://twitter.com/boydpaleo/status/1486500763190927363
- ↑ https://twitter.com/boydpaleo/status/1488217764951212035
- ↑ https://www.dmr.nd.gov/dmr/paleontology/fossil-digs/2022-public-fossil-dig-pembina-gorge
- ↑ https://www.dmr.nd.gov/ndgs/documents/newsletter/2017Winter/A%20New%20Addition%20to%20the%20Cretaceous%20Seaway%20of%20North%20Dakota.pdf
- ↑ Cite error: Invalid
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