Mosasaur
Overview
 
Mosasaurs are large extinct marine
Marine reptile
Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semi-aquatic life in a marine environment.The earliest marine reptiles arose in the Permian period during the Paleozoic era...

 lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

s. The first fossil remains were discovered in a limestone quarry at Maastricht
Maastricht
Maastricht is situated on both sides of the Meuse river in the south-eastern part of the Netherlands, on the Belgian border and near the German border...

 on the Meuse in 1764. Mosasaurs are now considered to be the closest relatives of snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s, due to cladistic analyses that have taken into account similarities in jaw and skull anatomies. Mosasaurs were varanoid
Varanoidea
Varanoidea is a superfamily of lizards, including the well-known family Varanidae . Also included in the Varanoidea are such extinct marine and semi-aquatic forms as mosasaurs and dolichosaurs, the venomous helodermatids , the Lanthanotidae , and the extinct Necrosauridae.Throughout their long...

s closely related to terrestrial monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

s. They probably evolved from semi-aquatic squamates known as aigialosaur
Aigialosaur
Aigialosauridae is family of Late Cretaceous semi-aquatic varanoid lizards, regarded by some paleontologists to form distinct monophyletic group and by others as an adaptive grade within the basal mosasauroids....

s, which were more similar in appearance to modern-day monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

s, in the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

.
Encyclopedia
Mosasaurs are large extinct marine
Marine reptile
Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semi-aquatic life in a marine environment.The earliest marine reptiles arose in the Permian period during the Paleozoic era...

 lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

s. The first fossil remains were discovered in a limestone quarry at Maastricht
Maastricht
Maastricht is situated on both sides of the Meuse river in the south-eastern part of the Netherlands, on the Belgian border and near the German border...

 on the Meuse in 1764. Mosasaurs are now considered to be the closest relatives of snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s, due to cladistic analyses that have taken into account similarities in jaw and skull anatomies. Mosasaurs were varanoid
Varanoidea
Varanoidea is a superfamily of lizards, including the well-known family Varanidae . Also included in the Varanoidea are such extinct marine and semi-aquatic forms as mosasaurs and dolichosaurs, the venomous helodermatids , the Lanthanotidae , and the extinct Necrosauridae.Throughout their long...

s closely related to terrestrial monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

s. They probably evolved from semi-aquatic squamates known as aigialosaur
Aigialosaur
Aigialosauridae is family of Late Cretaceous semi-aquatic varanoid lizards, regarded by some paleontologists to form distinct monophyletic group and by others as an adaptive grade within the basal mosasauroids....

s, which were more similar in appearance to modern-day monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

s, in the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

. During the last 20 million years of the Cretaceous Period (Turonian
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...

-Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

), with the extinction of the ichthyosaur
Ichthyosaur
Ichthyosaurs were giant marine reptiles that resembled fish and dolphins...

s and pliosaur
Pliosaur
Pliosauroidea is an extinct clade of marine reptiles. Pliosauroids, also commonly known as pliosaurs, are known from the Jurassic and Cretaceous Periods. The pliosauroids were short-necked plesiosaurs with large heads and massive toothed jaws. These swimming reptiles were not dinosaurs but distant...

s, mosasaurs became the dominant marine predators.

Description

Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, shallow epicontinental sea
Sea
A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...

s prevalent during the Late Cretaceous Period. Mosasaurs were so well adapted to this environment that they gave birth to live young
Vivipary
Vivipary has two different meanings. In animals, it means development of the embryo inside the body of the mother, eventually leading to live birth, as opposed to laying eggs...

, rather than return to the shore to lay eggs, as sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...

s do.

The smallest-known mosasaur was Carinodens
Carinodens
Carinodens is a genus of mosasaur. It was named in 1969 as a replacement for Compressidens, which was already in use for a mollusk. Measuring approximately in length, it is one of the smallest known mosasaurs. It is widely considered a sister taxon to Globidens. It also had round, blunt teeth for...

 belgicus
, which was about 3 metres (9.8 ft) to 3.5 metres (11.5 ft) long and probably lived in shallow waters near shore, cracking mollusks and sea urchins with its bulbous teeth. Larger mosasaurs were more typical: mosasaurs ranged in size up to 17 metres (55.8 ft). Hainosaurus
Hainosaurus
Hainosaurus is an extinct genus of marine lizard belonging to the mosasaur family. It was one of the largest mosasaurs, though its size has been revised more than once. At first it was estimated to be , and the largest mosasaurid. During the 1990s, its size was revised to long; more recently,...

holds the record for longest mosasaur, at 17.5 metres (57.4 ft).

Mosasaurs had a body shape similar to that of modern-day monitor lizards (varanids), but were more elongated and streamlined for swimming. Their limb bones were reduced in length and their paddles were formed by webbing between their elongated digit-bones. Their tails were broad, and supplied the locomotive power. This method of locomotion may have been similar to that used by the conger eel or sea snakes today. However, more recent evidence suggests that many advanced mosasaurs had large crescent-shaped flukes on the ends of their tails similar to those of shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s and ichthyosaur
Ichthyosaur
Ichthyosaurs were giant marine reptiles that resembled fish and dolphins...

s. Rather than snake-like undulatory movement, the body probably remained stiff in these mosasaurs to improve hydrodynamic efficiency through the water while the end of the tail provided strong propulsion. The animal may have lurked and pounced rapidly and powerfully on passing prey, rather than hunting for it.

Mosasaurs had a double-hinged jaw and flexible skull (much like that of a snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

), which enabled them to gulp down their prey almost whole, a snakelike habit which helped identify the unmasticated gut contents fossilized within mosasaur skeletons. A skeleton of Tylosaurus
Tylosaurus
Tylosaurus was a mosasaur, a large, predatory marine lizard closely related to modern monitor lizards and to snakes.-Paleobiology:...

 proriger
from South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

 included remains of the diving seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

 Hesperornis
Hesperornis
Hesperornis is a genus of flightless aquatic birds that spanned the first half of the Campanian age of the Late Cretaceous period . One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an important early find in the history of avian...

, a marine bony fish, a possible shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

 and another, smaller mosasaur (Clidastes). Mosasaur bones have also been found with shark teeth embedded in them.

Based on features such as the double row of pterygoid ("flanged") teeth on the palate, the double-hinged jaw, modified/reduced limbs and probable methods of locomotion, many researchers believe that snakes and mosasaurs may have had a common ancestor. This theory was first suggested in 1869, by Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...

, who coined the term "Pythonomorpha" to include them. The idea lay dormant for more than a century, before being revived in the 1990s.

Soft tissue

Despite the relatively high number of mosasaur remains collected worldwide, knowledge of the nature of their skin coverings remains in its early stages. An incredibly small amount of mosasaurid specimens collected from around the world retain fossilized scale imprints; this lack of knowledge is possibly due to the delicate nature of the scales, which nearly eliminates possibility of preservation, in addition to the preservation sediments types and the marine conditions under which the preservation occurred. Until the discovery of several mosasaur specimens along with their remarkably well preserved scale imprints from late Maastricht
Maastricht
Maastricht is situated on both sides of the Meuse river in the south-eastern part of the Netherlands, on the Belgian border and near the German border...

ian deposits of the Muwaqqar Chalk Marl Formation of Harrana
Harrana
Harrana, named after Qasr Kharana, an archeological Umayyad desert palace in the area, is part of the Jordan eastern plateau some 60 kilometers southeast of Amman city. ....

 in Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...

, knowledge of the nature of mosasaur integument was mainly based on very few accounts describing early mosasaur fossils dating back to the upper Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...

-lower Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

 such as the famous Tylosaurus
Tylosaurus
Tylosaurus was a mosasaur, a large, predatory marine lizard closely related to modern monitor lizards and to snakes.-Paleobiology:...

 specimen (KUVP-1075) from Cove County, Kansas. Material from Jordan has shown that the body of mosasaurs, as well as the membrane between the fingers and toes, was covered with small overlapping diamond-shaped scales resembling those of snakes. Much like modern reptiles, there existed regional variations in the type and size of the scales that covered the mosasaurs. In Harrana specimens, two types of scales were observed on a single specimen, keeled scales covering the upper regions of the body as well as smooth scales covering the lower regions. As ambush predators, lurking and quickly capturing prey using stealth tactics, it is suggested mosasaurs benefited greatly from the non-reflective keeled scales.

More recently, a well preserved fossil of Platecarpus tympaniticus
Platecarpus
Platecarpus is an extinct genus of aquatic lizard belonging to the mosasaur family, living around 75 million years ago during the end of the Cretaceous period. Fossils have been found in Belgium and the United States as well as a possible specimen in Africa. Platecarpus probably fed on fish,...

has been found that preserves not only skin impressions, but also internal organs. There are several reddish areas in the fossil that may represent the heart, lungs, and kidneys. The trachea is also preserved along with part of what may be the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

 in the eye. The placement of the kidneys is farther forward in the abdomen than it is in monitor lizards, and is more similar to that of cetaceans. As in cetaceans, the bronchi leading to the lungs run parallel to each other instead of splitting apart from one another as in monitors and other terrestrial reptiles. In mosasaurs, these features may be internal adaptations to a fully marine lifestyle.

In 2011, collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

 protein was recovered from a Prognathodon
Prognathodon
Prognathodon is an extinct genus of marine reptile belonging to the mosasaur family. It had protective bony rings surrounding its eye sockets, indicating it lived in deep water. its fossil remains have been found in the U.S.A , Canada , Belgium, New Zealand, Morocco and The Netherlands...

humerus dated to the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

.

Environment

Sea levels were high during the Cretaceous Period, causing marine transgressions in many parts of the world and a great inland seaway
Western Interior Seaway
The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...

 in what is now North America. Mosasaur fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s have been found in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

, Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...

, Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, and on Vega Island
Vega Island
Vega Island is a small island to the northwest of James Ross Island, on the Antarctic Peninsula.- See also :* Composite Antarctic Gazetteer* List of Antarctic islands south of 60° S* SCAR* Territorial claims in Antarctica- References :...

 off the coast of Antarctica. Mosasaurs have been found in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 in Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...

 and Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

 and in much of the contiguous United States. Complete or partial specimens have been found in Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...

, Mississippi
Mississippi
Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...

, Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...

, and Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

 -- as well as in states covered by the Cretaceous seaway: Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

, southwest Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...

, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...

, Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...

, Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

, Nebraska
Nebraska
Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....

, South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

, Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

, and the Pierre Shale
Pierre Shale
The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from North Dakota to New Mexico....

/Fox Hills
Fox Hills
Fox Hills may refer to:* Fox Hills, Staten Island* Fox Hills, Culver City, California...

 formations of North Dakota
North Dakota
North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....

. Lastly, mosasaur bones and teeth are also known from California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, and Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

.

Many of the so-called 'dinosaur' remains found on New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 are actually mosasaurs and plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...

s, both being Mesozoic predatory marine reptiles.

Discovery

The first publicized discovery of a partial fossil mosasaur skull in 1764 by quarry-workers in a subterranean gallery of a limestone quarry in Mount Saint Peter
Mount Saint Peter
Mount Saint Peter is a ridge running north to south between the valleys of the Geer and the Meuse from Maastricht in the Netherlands to the area of Liège in Belgium....

, near the Dutch city of Maastricht
Maastricht
Maastricht is situated on both sides of the Meuse river in the south-eastern part of the Netherlands, on the Belgian border and near the German border...

, preceded any major dinosaur fossil discoveries but remained little known. However, a second find of a partial skull drew the Age of Enlightenment
Age of Enlightenment
The Age of Enlightenment was an elite cultural movement of intellectuals in 18th century Europe that sought to mobilize the power of reason in order to reform society and advance knowledge. It promoted intellectual interchange and opposed intolerance and abuses in church and state...

's attention to the existence of fossilized animals that were different from any known living creatures. When the specimen was discovered between 1770 and 1774, Johann Leonard Hoffmann, a surgeon and fossil-collector, corresponded about it with the most influential scientists of his day, making the fossil famous. The original owner though was Godding, a canon of Maastricht cathedral.

When the French Revolutionary forces occupied Maastricht in 1794, the carefully hidden fossil was uncovered, after a reward, it is said, of six hundred bottles of wine, and transported to Paris. After it had been earlier interpreted as a fish, a crocodile and a sperm whale, the first to understand its lizard affinities was the Dutch scientist Adriaan Gilles Camper in 1799. In 1808 Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...

 confirmed this conclusion, although le Grand Animal fossile de Maëstricht was not actually named Mosasaurus ('Meuse
Meuse River
The Maas or Meuse is a major European river, rising in France and flowing through Belgium and the Netherlands before draining into the North Sea...

 reptile') until 1822 and not given its full species name, Mosasaurus hoffmannii, until 1829. Several sets of mosasaur remains, that had been discovered earlier at Maastricht but were not identified as mosasaurs until the nineteenth century, have been on display in the Teylers Museum
Teylers Museum
Teyler's Museum , located in Haarlem, is the oldest museum in the Netherlands. The museum is in the former home of Pieter Teyler van der Hulst . He was a wealthy cloth merchant and Amsterdam banker of Scottish descent, who bequeathed his fortune for the advancement of religion, art and science...

, Haarlem
Haarlem
Haarlem is a municipality and a city in the Netherlands. It is the capital of the province of North Holland, the northern half of Holland, which at one time was the most powerful of the seven provinces of the Dutch Republic...

, procured from 1790.

The Maastricht limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 beds were rendered so famous by the Mosasaur discovery that they have given their name to the final six-million-year epoch of the Cretaceous, the Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

.

Classification

  • Family Mosasauridae
    • Subfamily Tylosaurinae
      • Hainosaurus
        Hainosaurus
        Hainosaurus is an extinct genus of marine lizard belonging to the mosasaur family. It was one of the largest mosasaurs, though its size has been revised more than once. At first it was estimated to be , and the largest mosasaurid. During the 1990s, its size was revised to long; more recently,...

      • Tylosaurus
        Tylosaurus
        Tylosaurus was a mosasaur, a large, predatory marine lizard closely related to modern monitor lizards and to snakes.-Paleobiology:...

      • Taniwhasaurus
        Taniwhasaurus
        Taniwhasaurus is an extinct genus of mosasaur, a carnivorous, marine reptile which inhabited New Zealand, Japan and Antarctica. The genus was a close relative of the genera Tylosaurus and Hainosaurus.-Species:-T...

    • Subfamily Plioplatecarpinae
      • Platecarpus
        Platecarpus
        Platecarpus is an extinct genus of aquatic lizard belonging to the mosasaur family, living around 75 million years ago during the end of the Cretaceous period. Fossils have been found in Belgium and the United States as well as a possible specimen in Africa. Platecarpus probably fed on fish,...

      • Angolasaurus
        Angolasaurus
        Angolasaurus is an extinct genus of mosasaur found in the Upper Cretaceous of Angola and described by Miguel Telles Antunes in 1964....

      • Ectenosaurus
        Ectenosaurus
        Ectenosaurus is a genus of mosasaur from the Late Cretaceous period....

      • Selmasaurus
        Selmasaurus
        Selmasaurus is a genus of medium-sized plioplatecarpine mosasaur from the Upper Cretaceous Mooreville Chalk Formation of western Alabama...

      • Igdamanosaurus
        Igdamanosaurus
        Igdamanosaurus is a genus of mosasaur from the Maastrichtian stage of the Late Cretaceous of Africa.-References:* Fossil Vertebrates - Fauna and Concepts by W. Sargeant and William A.S. Sargeant...

      • Yaguarasaurus
        Yaguarasaurus
        Yaguarasaurus was a genus of mosasaur from the Late Cretaceous period of Colombia, South America. The remains discovered were defined as a new genus and species of the tribe Plioplatecarpini, Yaguarasaurus columbianus, by the Colombian paleontologist María Páramo, former director of the Museo de...

      • Plioplatecarpus
        Plioplatecarpus
        Plioplatecarpus is a genus of mosasaur lizard. Like all mosasaurs, it lived in the late Cretaceous period, about 83.5 million years ago.-Description:...

    • Subfamily Mosasaurinae
      • Dallasaurus
        Dallasaurus
        Dallasaurus is a basal mosasauroid from the Upper Cretaceous of North America. The genus is based upon two partial skeletons recovered from the Arcadia Park Shale , approximately 15 meters above its contact with the older Kamp Ranch Limestone in Dallas County in north-central Texas...

      • Clidastes
        Clidastes
        Clidastes is an extinct genus of mosasaur lizard from marine environments of the Late Cretaceous.Clidastes was an agile and fast swimmer that cruised the surface or shallow waters hunting for fish, flying reptiles and anything that got too close.- Appearance :Clidastes was the smallest of the...

      • Mosasaurus
        Mosasaurus
        Mosasaurus is a genus of mosasaur, carnivorous, aquatic lizards, somewhat resembling flippered crocodiles, with elongated heavy jaws. The genus existed during the Maastrichtian age of the Cretaceous period , around 70-65 millions years ago in the area of modern Western Europe and North America...

      • Moanasaurus
        Moanasaurus
        Moanasaurus was a genus of mosasaur from the Late Cretaceous period. Its fossil remains have been discovered in the North Island of New Zealand. Moanasaurus was a very large mosasaurine known originally from a disarticulated skull, vertebrae, ribs and paddle bones...

      • Amphekepubis
        Amphekepubis
        Amphekepubis is a genus of mosasaur from the Late Cretaceous of Mexico.-References:*-External links:*...

      • Plotosaurus
        Plotosaurus
        Plotosaurus is an extinct genus of mosasaur from the Upper Cretaceous of Fresno County, California. Originally named Kolposaurus by Berkeley paleontologist Charles Lewis Camp in 1942, it was changed to Plotosaurus in 1951 when Camp discovered the name had already been assigned to a type of...

      • Globidens
        Globidens
        Globidens is an extinct genus of mosasaur lizard.Globidens alabamaensis was first described by Gilmore . A second species was described by Russell . The third North American species Globidens ("Globe teeth") is an extinct genus of mosasaur lizard.Globidens alabamaensis was first described by...

      • Prognathodon
        Prognathodon
        Prognathodon is an extinct genus of marine reptile belonging to the mosasaur family. It had protective bony rings surrounding its eye sockets, indicating it lived in deep water. its fossil remains have been found in the U.S.A , Canada , Belgium, New Zealand, Morocco and The Netherlands...

      • Plesiotylosaurus
        Plesiotylosaurus
        Plesiotylosaurus is a genus of mosasaur from the Maastrichtian stage of the Late Cretaceous of North America.-References:* Dinosaurs and Other Mesozoic Reptiles of California by Richard P. Hilton, Kevin Padian, and Ken Kirkland...

      • Carinodens
        Carinodens
        Carinodens is a genus of mosasaur. It was named in 1969 as a replacement for Compressidens, which was already in use for a mollusk. Measuring approximately in length, it is one of the smallest known mosasaurs. It is widely considered a sister taxon to Globidens. It also had round, blunt teeth for...

    • Subfamily Halisaurinae
      • Eonatator
        Eonatator
        Eonatator is a genus of halisaurine mosasaur from the Upper Cretaceous of North America and Europe. Originally, this taxon was included within Halisaurus, but was placed in its own genus...

      • Halisaurus
        Halisaurus
        Halisaurus is an extinct genus of marine lizard belonging to the mosasaur family. With a length of 3–4 m , it was small compared to most other mosasaurs. It was named by Othniel Charles Marsh in 1869, but renamed Baptosaurus by Marsh in 1870, who thought the name was already in use by a fish...



Incertae sedis
  • Liodon
    Liodon
    Liodon is a genus of mosasaur from the Late Cretaceous. Remains assigned to this genus have been found in Africa, Asia, Europe, America and South America, and New Zealand. It was first named by Richard Owen as Leiodon, but that name was already in use for a fish, necessitating the name...

  • Goronyosaurus
    Goronyosaurus
    Goronyosaurus nigeriensis is a species of crocodile-like mosasaur from the Late Cretaceous of Sokoto State, Niger and northwestern Nigeria.-External links:*...

  • Pluridens
    Pluridens
    Pluridens walkeri was a species of ichthyosaur-like mosasaur. It lived in what are Niger and Nigeria, from the Late Cretaceous....

  • Kourisodon
    Kourisodon
    Kourisodon is an extinct genus of mosasaur. Fossils have been found from Vancouver Island in British Columbia that date back to the late Santonian stage of the Late Cretaceous.-References:*-External links:* in the Paleobiology Database...

  • Russellosaurus
    Russellosaurus
    Russellosaurus is a basal mosasauroid from the Upper Cretaceous of North America. The genus was described from a skull discovered in an exposure of the Arcadia Park Shale at Cedar Hill, Dallas County in south-central Texas...

  • Tethysaurus
    Tethysaurus
    Tethysaurus was a genus of mosasaur from the Early Turonian period. The only species is Tethysaurus nopscai. The name means "Tethys' lizard of Nopsca", a reference to the Greek goddess of the sea Tethys and to the Hungarian paleontologist Baron Ferenc Nopsca, who made...


Phylogeny

Cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...

 of mosasaurs and related taxa modified from Bell and Polcyn, 2005:

Evolutionary antecedents

Based on features such as the loosely-hinged jaw, modified/reduced limbs and probable locomotion, many researchers believe that snakes share a common marine ancestry with mosasaurs, a suggestion advanced in 1869, by Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...

, who coined the term "Pythonomorpha" to unite them. The idea lay dormant for more than a century, to be revived in the 1990s. Recently, the discovery of Najash rionegrina
Najash rionegrina
Najash is an extinct genus of basal snake. Like a number of other Cretaceous snakes , it had two hind-limbs. The fossils were found in a land-based deposit, and the robust backbone vertebrae and rear legs of the snake were adapted to a burrowing, subterranean environment...

, a fossorial snake from South America cast doubt on the marine origin hypothesis.

On 2005-11-16, research reported in Netherlands Journal of Geosciences, confirmed that the recently uncovered Dallasaurus turneri
Dallasaurus
Dallasaurus is a basal mosasauroid from the Upper Cretaceous of North America. The genus is based upon two partial skeletons recovered from the Arcadia Park Shale , approximately 15 meters above its contact with the older Kamp Ranch Limestone in Dallas County in north-central Texas...

is an early link between land-based monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

s (such as the Komodo dragon
Komodo dragon
The Komodo dragon , also known as the Komodo monitor, is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang and Gili Dasami. A member of the monitor lizard family , it is the largest living species of lizard, growing to a maximum length of in rare cases...

) and the aquatic mosasaurs.

Distribution

The following is a list of geologic formations that have produced mosasaur fossils.

Name Age Location Notes

Moreno Formation
Moreno Formation
The Moreno Formation is a Mesozoic geologic formation. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.-Dinosaurs:-Mosasaurs:-Plesiosaurs:-Turtles:-See also:...


Niobrara Formation
Niobrara Formation
The Niobrara Formation, also called the Niobrara Chalk , is a geologic formation in North America that was laid down between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian ages of the Late Cretaceous. It is composed of two structural units, the Smoky Hill Chalk Member...


In popular culture

  • Mosasaurs appear in the BBC television series Sea Monsters.
  • Mosasaurs also feature heavily in the ITV television series Primeval. In this show, the mosasaurs are depicted incorrectly as having skin more like a crocodile
    Crocodile
    A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

    's.
  • A highly evolved mosasaur appeared in an episode of Godzilla: The Series
    Godzilla: The Series
    Godzilla: The Series is an American/Japanese animated television series which originally aired on Fox in the United States. The show premiered on September 12, 1998, and is a direct sequel to the American Godzilla remake.-Plot:...

    . It was inhabiting Loch Ness
    Loch Ness
    Loch Ness is a large, deep, freshwater loch in the Scottish Highlands extending for approximately southwest of Inverness. Its surface is above sea level. Loch Ness is best known for the alleged sightings of the cryptozoological Loch Ness Monster, also known affectionately as "Nessie"...

     as the legendary Loch Ness Monster
    Loch Ness Monster
    The Loch Ness Monster is a cryptid that is reputed to inhabit Loch Ness in the Scottish Highlands. It is similar to other supposed lake monsters in Scotland and elsewhere, though its description varies from one account to the next....

    .
  • The IMAX 3D film "Sea Monsters" features several mosasaurs (including Tylosaurus and Platecarpus
    Platecarpus
    Platecarpus is an extinct genus of aquatic lizard belonging to the mosasaur family, living around 75 million years ago during the end of the Cretaceous period. Fossils have been found in Belgium and the United States as well as a possible specimen in Africa. Platecarpus probably fed on fish,...

    ) with detailed animated recreations of their movements and activities.
  • In Disney's Fantasia
    Fantasia (film)
    Fantasia is a 1940 American animated film produced by Walt Disney and released by Walt Disney Productions. The third feature in the Walt Disney Animated Classics series, the film consists of eight animated segments set to pieces of classical music conducted by Leopold Stokowski, seven of which are...

    , there is a scene where a pod of mosasaurs are swimming by and one of them grabs a pteranodon
    Pteranodon
    Pteranodon , from the Late Cretaceous geological period of North America in present day Kansas, Alabama, Nebraska, Wyoming, and South Dakota, was one of the largest pterosaur genera and had a maximum wingspan of over...

    .

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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