Mosasaurus

## MosasaurusMeuse River Lizard

### Temporal Range

82.7 - 66 million years ago, Campanian - Maastrichtian Stage, Late Cretaceous Period

### Episodes

* Coasts (Segments 1 and 4)
* Oceans (Segments 1 and 4)
* Could T. rex Really Swim? (Cameo)
* What Else Lived Alongside The Dinosaurs?
* How Fast Was A Mosasaur?

## Characteristics

### Diet

Carnivore

* **Skull Length** of 1.86 - 2.14 meters (6 - 7 feet)
* **Top Speed** of 48.3 kilometers (30 miles) per hour
* **Acceleration** of 9.75 - 11.4 meters (32 - 37 feet) per second

 **Main** Segments

MainSegments

***“ A Mosasaur, a giant marine lizard over twice the size of a tyrannosaur, and weighing over 15 tonnes. It's the largest predator on the planet. ”***

― **David Attenborough**, *Coasts*
***Mosasaurus*** (Meuse River Lizard, for it was first found in a chalk quarry close to the river) is a genus of mosasaur that lived 82.7 - 66 million years ago, from the Campanian to the Maastrichtian stage of the Late Cretaceous Period. Its remains were found on all seven continents, and (along with some of its other large relatives), as one of the largest marine reptiles to ever exist, it was the apex predator of the oceans and seas it lived in.

There are currently at least five valid species of *Mosasaurus*. The one mostly shown on Prehistoric Planet is the largest species, *Mosasaurus hoffmannii*, referred to as "Hoffmann's Mosasaur" in Coasts, with the species name honoring Johann Leonard Hoffmann, an army surgeon and amateur geologist who was involved in the animal's discovery. Prehistoric Planet also appears to show another species, *Mosasaurus hobetsuensis* of the Hakobuchi Formation in Hokkaido, Japan, though, given its dubious validity, it is possible that this is also *Mosasaurus hoffmannii*.

## Paleobiology

### Size and Physique

*Mosasaurus* is the last and the largest of the mosasaurs, massive marine lizards that eventually became the dominant predators of the oceans and seas during the Late Cretaceous Period. These animals are best described as being like monitor lizards mixed with orcas, possessing elongated, streamlined bodies and two pairs of flippers. It was originally believed that mosasaurs were eel-shaped and thus moved like an eel or a sea snake. Today, however, it is understood that the more advanced species of mosasaurs had crescent-shaped tail fins like those of sharks and ichthyosaurs, albeit upside-down, with the lower part being longer than the upper part.

*Mosasaurus* was originally thought to be 17 - 18 meters long, based on the idea that the body is ten times longer than the skull. However, no explicit explanation has been given regarding this 1:10 estimate in the original 1967 study that brings the ratio up, and today, lengths of 17 - 18 meters are considered to be overestimations, with revisions bringing up a more plausible skull-to-body ratio of 1:7, resulting in a maximum length of 10 meters (33 feet) and a body mass of 10 metric tons (11 short tons), and more recent calculations as of 2022 bringing up a maximum length of 13 meters (42 feet) and a maximum weight of 5.5 metric tons (6.1 short tons), though Prehistoric Planet considers it to still be plausible that *Mosasaurus* reached lengths of 15 meters (50 feet) and weights of up to 15 metric tons (16.5 short tons),. Even with these revisions, however, the formidable *Mosasaurus hoffmannii*, along with some of its large relatives like *Tylosaurus* and *Prognathodon*, are the apex predators of the Late Cretaceous oceans and seas. Smaller mosasaurs like *Phosphorosaurus* and other inhabitants would hide whenever one *Mosasaurus* is on the prowl nearby. And while pods of *Tuarangisaurus* are willing to fight off medium-sized mosasaurs like *Kaikaifilu*, which is only 10 meters (33 feet) long and 3 metric tons (3.3 short tons) in weight, they all immediately flee once attacked by *Mosasaurus*, though, given the animal's tremendous speed, when it successfully launches an ambush, the force of its strike alone is enough to kill prey before they even know what happened.

### Jaws and Dentition

***“ Mosasaurs are giant lizards, and have both a lizard's forked tongue, and, during the mating season, a lizard's colorful skin. ”***

― **David Attenborough**, *Coasts*
Much like snakes, mosasaurs have double-hinged jaws and flexible skulls to swallow their prey whole. They also possess four types of teeth, with one set being on the pterygoid bone (which forms the palate, the roof of the mouth), which helped secure prey and even ratchet them further into the mosasaur's throat. *Mosasaurus* has teeth specialized for cutting up prey, with *M. hoffmannii* possessing two premaxillary teeth, 14 - 16 maxillary teeth, 14 dentary (lower jaw) teeth, and eight pterygoid teeth, all bearing fine serrations (another species, *M. missouriensis*, also possesses finely-serrated teeth). Like lizards today, mosasaurs likely had their teeth sunken into their gums, as is shown on Prehistoric Planet.

### Senses

Mosasaurs are believed to have forked tongues, much like lizards and snakes, which collect chemical particles from the environment with their tongues and insert them into the voremonasal organ (also known as Jacobson's organ) by their palate. This feature still works very well for sea snakes, so it would also work just fine for mosasaurs. While usually depicted as long, slim and deeply-forked like those of snakes, Prehistoric Planet instead modeled their tongues after the shorter, thicker, and less-mobile tongues of anguimorph lizards, since mosasaurs are believed to be part of the anguimorph group themselves. However, while this means that mosasaurs are in the same group as varanids (monitor lizards), they do not seem that close to them, and mosasaurs may possibly not be anguimorphs at all.

### Speed

***“ Mosasaurus is an ambush predator. This enormous animal uses its huge tail to accelerate with astonishing speed. ”***

― **David Attenborough**, *Oceans*
The large, crescent-shaped tails of mosasaurs allow them keep their bodies stiff while their tails propelled them forward with great force that enables them cover a distance equivalent to 75% of their body length. As Prehistoric Planet: Uncovered brings up, *Mosasaurus* can accelerate to a top speed of 48.3 kilometers (30 miles) per hour in a single second.

Prehistoric Planet depicts *Mosasaurus* relying on the "C-start" technique, a reflex used by fish and amphibians today, mostly to quickly escape predators but potentially also for ambushing prey. As the name suggests, animals that use this technique first rotate their head about the center of mass towards the direction of where they plan to go (thus forming a C-shape), before suddenly rushing towards their target or destination.

### Prehistoric Planet's Depiction

*Main: *Mosasaurus* on Prehistoric Planet*

Main: *Mosasaurus* on Prehistoric Planet

***“ Mosasaurs were seagoing lizards. Think of a giant, swimming, whale-sized Komodo Dragon. Tapered snout, rough skin, four fins instead of normal limbs, and a long tail that would look a lot like a shark tail, but upside down. That's basically a mosasaur. ”***

― **Dr. Michael Habib**, *University of California*
Prehistoric Planet depicts *Mosasaurus* with pebbly, dark brown skin and a white underside, since most animals, predator and prey alike, are known to rely on countershading to effectively camouflage themselves, blending in with darkness when seen from above, and blending in with light when seen from below. As seen in Coasts, during the mating season, as it sheds its skin in flakes like other lizards do, *Mosasaurus* displays a tone of bright red on its back and face to attract females.

***“ Deep beneath the water’s surface, the world’s largest predator — the Mosasaurus — lies in wait to ambush unsuspecting prey. ”***

― The official Apple TV+ episode synopsis for *Oceans*
*Mosasaurus* appears in the first segment of Coasts, pursuing a family of *T. rexes* as they swim through the open seas, eventually snatching one of the juveniles. Later on, in the fourth segment of Coasts, a male *Mosasaurus* relaxes in a cleaning station in southern Europe before fighting a younger male trying to take his territory. The massive oceanic predator is briefly seen in the first segment of Oceans, where its threatening presence ominously looms over a reef in Japan. The danger *Mosasaurus* poses is made apparent in the fourth segment of Oceans, where it ambushes a pod of *Tuarangisaurus* in a quick burst of speed that kills its target outright. This speed serves as the main focus of the Prehistoric Planet: Uncovered segment "How Fast Was A Mosasaur?", which brings up various techniques for achieving such speed like the C-start, and, following a unique scientific study ran four times by Prehistoric Planet's research team, concludes that *Mosasaurus* can accelerate to 30 miles (48.3 kilometers) an hour in just one single second.

## Paleoecology

### Paleoenvironment

*Main: Western Interior Seaway, Tethys Ocean, López de Bertodano Formation*

Main: Western Interior Seaway, Tethys Ocean, López de Bertodano Formation

***“ In southern Europe, where the Atlantic meets the great Tethys Sea, coastal life perhaps reaches its greatest diversity. Rising sea level means that there are countless submerged islands covered with sponges, clams, and corals. Corals take advantage of the sunshine in these shallows, forming partnerships with algae that grow within their tissues. They collect tiny particles of food floating in the ocean currents. Myriads of these marine creatures encrust the solid rock. But one rock here appears surprisingly bare. Beyond is a sheer dropoff and the deep sea, home to oceanic predators, and danger for unwary reef fish. ”***

― **David Attenborough**, *Coasts*
*Mosasaurus* has been found in several sites all over the world. Fossils in the midwest and east coast of the United States and Canada show that it was present in the inland sea that splits the continent of North America in half. Brazil and Argentina have also yielded fossils of *Mosasaurus*. Evidence of its dominion in the Atlantic Ocean and Tethys Ocean is made apparent by remains found in Europe, Turkey, Russia, the Levant, and the African coastline from Morocco to South Africa. Fossils found in the López de Bertodano Formation indicate that *Mosasaurus* may have also prowled the cold waters of Antarctica, though it's been theorized that these remains may actually be those of *Moanasaurus*, a slightly smaller mosasaur known from the Tahora Formation in New Zealand.Having been present in several oceans with diverse ecosystems and wildly varying climates, from tropical to temperate, and even subpolar regions, *Mosasaurus* has proven to be a greatly-successful species and (along with the relatives it coexisted with) the true master of the ocean. At the height of its power, its superiority was only halted by the Cretaceous-Paleogene Extinction Event, which wiped out three-quarters of life on Earth 66 million years ago.

***“ Canyons in the atoll walls lead from the atolls to fresh feeding grounds. This deep water attracts not just the hungry elasmosaurs, but the predators that hunt them. The biggest in the ocean. Fifty foot-long Mosasaurus. ”***

― **David Attenborough**, *Oceans*
Some studies indicate that, in terms of depth and distance to the shore, *Mosasaurus* preferred to be close to the coast, within depths of 40-50 meters (131 - 164 feet). However, more recent studies, involving the analysis of rare earth elements, indicate that *Mosasaurus* dwelled in offshore environments deeper than 50 meters (164 feet).

### Hunting Tactics and Feeding Preferences

***“ Camouflaged against the dark canyon floor, the Mosasaur can approach unseen, waiting for a young, inexperienced individual, the ideal victim. ”***

― **David Attenborough**, *Oceans*
While *Mosasaurus* is able to cover great distances in a short amount of time, its hunting strategy does not rely on the long-term pursuit of prey. Rather, they prefer to camouflage themselves with their countershaded bodies, stealthily ambush their prey and, in a short burst of speed, strike them and kill them outright.

*Mosasaurus* is believed to have a generalist diet, willing to go after fish like *Xiphactinus*, sharks, turtles, smaller mosasaurs, and anything else that is within its reach. Like any predator, *Mosasaurus* is opportunistic, willing to chase and catch even a single juvenile *T. rex* that would barely serve to satiate its hunger.

### Agonistic Behavior

***“ A rival, a younger male challenging for this territory. The old male is heavier, over 15 tonnes, but his rival is more nimble. When they are as evenly matched as this, these fights can be lethal. Mosasaurs have been found with the shattered teeth of rivals embedded in their skulls. ”***

― **David Attenborough**, *Coasts*
When it comes to competition, mosasaurs are highly territorial, and confrontations can become brutal and outright fatal, with some remains showing crushed skulls, broken necks, and even dismemberment. *Mosasaurus* also shared the oceans with other predators, and was thus involved in conflict with other species. The young could be eaten by sharks or the giant fish *Xiphactinus*, and some mosasaurs grew around 12 meters (40 feet) long, almost as big as *Mosasaurus* itself. Some battles can be prevented with niche partitioning. For example, *Prognathodon* was more suited for going after more robust prey like turtles, and while *Mosasaurus* is also capable of going after turtles, it had a more generalist diet and thus didn't fully compete with *Prognathodon*. This is supported by the discovery of stomach contents from both, with *Prognathodon* containing hard prey like turtles and ammonites and *Mosasaurus* containing soft prey like fish. Even so, competition cannot be fully avoided, as a fatal, concentrated blow to a subadult *Mosasaurus* skull is, at one point, interpreted to be due to an attack by *Tylosaurus*, which possesses a robust, arrow-shaped snout that was likely able to deal a coordinated strike and cause fractures like that.

### Grooming and Mating Habits

***“ This is Hoffmann's Mosasaur, the ocean's deadliest predator, but he's not here to eat, he's come to be cleaned. ”***

― **David Attenborough**, *Coasts*
Despite its deadly nature, as a living being, *Mosasaurus* also has its more peaceful moments. Prehistoric Planet speculates that, as a lizard, it would have put on new hues of color or intensified preexisting displays during the mating season to help attract mates, as seen when the *Mosasaurus* in Coasts turns its back and face bright red. They would have also likely benefited from cleaning stations, letting fishes and shrimps clean off scraps and shedding skin and just outright relaxing, with only other large mosasaurs able to capitalize on this moment of weakness and ambush them, though this is not a guaranteed means of bringing down a mosasaur, and may even backfire if the assaulted mosasaur is just as skilled as the attacker.

## Trivia

As confirmed by Dr. Darren Naish, lead consultant of Prehistoric Planet, the *Mosasaurus hoffmannii* in the fourth segment of Coasts is officially nicknamed "Hoff".

## References

### General

1. ↑ 1.0 1.1 *The Princeton Field Guide to Mesozoic Sea Reptiles*
2. ↑ 2.0 2.1 A giant mosasaur (Reptilia, Squamata) with an unusually twisted dentition from the Argille Scagliose Complex (late Campanian) of Northern Italy
3. ↑ Giant *Mosasaurus hoffmannii* (Squamata, Mosasauridae) from the Late Cretaceous (Maastrichtian) of Penza, Russia
4. ↑ Anatomy and functional morphology of the largest marine reptile known, *Mosasaurus hoffmanni* (Mosasauridae, Reptilia) from the Upper Cretaceous, Upper Maastrichtian of The Netherlands
5. ↑ Systematics and morphology of American mosasaurs
6. ↑ Lepidosaurian diversity in the Mesozoic–Palaeogene: the potential roles of sampling biases and environmental drivers
7. ↑ Giant *Mosasaurus hoffmannii* (Squamata, Mosasauridae) from the Late Cretaceous (Maastrichtian) of Penza, Russia
8. ↑ Osteology and taxonomy of *Mosasaurus conodon* Cope 1881 from the Late Cretaceous of North America
9. ↑ Rediagnosis and redescription of *Mosasaurus hoffmannii* (Squamata: Mosasauridae) and an assessment of species assigned to the genus *Mosasaurus*
10. ↑ Biostratigraphy of the Mosasauridae (Reptilia) from the Cretaceous of Antarctica
11. ↑ A new Plotosaurini mosasaur skull from the upper Maastrichtian of Antarctica. Plotosaurini paleogeographic occurrences
12. ↑ Anatomy and functionality of the largest marine reptile known, *Mosasaurus hoffmannii* (Mosasauridae, Reptilia) from the Upper Cretaceous, Upper Maastrichtian of The Netherlands
13. ↑ Habitat preference of mosasaurs indicated by rare earth element (REE) content of fossils from the Upper Cretaceous marine deposits of Alabama, New Jersey, and South Dakota (USA)
14. ↑ A small, exquisitely preserved specimen of *Mosasaurus missouriensis* (Squamata, Mosasauridae) from the upper Campanian of the Bearpaw Formation, western Canada, and the first stomach contents for the genus
15. ↑ Unusual death of a Cretaceous giant

### Dr. Darren Naish

1. ↑ Openings on mosasaur palates may reveal the location of the Jacobson's organ, a palatal structure that lizards and snakes use in collecting chemicals from the environment via the tongue.
2. ↑ The tongues of the mosasaurs were based off of the shorter, thicker, and less-mobile tongues of anguimorph lizards.
3. ↑ Mosasaurs being close relatives of monitor lizards isn't really true. Assuming that mosasaurs are part of same group as monitor lizards, it appears that they don't seem particularly close, and it is possible that mosasaurs may not even be anguimorphs to begin with.
4. ↑ The big male *Mosasaurus hoffmannii* in the fourth segment of Coasts is nicknamed "Hoff".

### Prehistoric Planet

1. ↑ 1.0 1.1 1.2 1.3 As stated in Coasts.
2. ↑ 2.0 2.1 As stated in Oceans.
3. ↑ 3.0 3.1 3.2 As stated in Prehistoric Planet: Uncovered - What Else Lived Alongside The Dinosaurs?
4. ↑ 4.0 4.1 4.2 4.3 As stated in Prehistoric Planet: Uncovered - How Fast Was A Mosasaur?
5. ↑ I Know Dino: The Big Dinosaur Podcast, Episode 446: Dinosaur-era Oceans and Darren Naish from Prehistoric Planet 2