Mosasaur

Mosasaurs (from Latin Mosa, which means 'Meuse,' and Greek sauros, which means 'lizard') are a group of extinct, enormous marine reptiles that are divided into 40 species. In 1764, their first fossils were discovered in a limestone quarry in Maastricht on the Meuse. They are members of the Squamata order, which includes lizards and snakes.

Mosasaurs are thought to have descended from an extinct genus of aquatic lizards known as aigialosaurs during the Early Cretaceous Period. With the extinction of ichthyosaurs and pliosaurs over the last 20 million years of the Cretaceous epoch (Turonian–Maastrichtian ages), mosasaurs became the main marine predators. They went extinct around 66 million years ago as a result of the K-Pg event, which occurred at the end of the Cretaceous period.

Description 

Mosasaurs were air-breathing, strong swimmers, and well-suited to life in the warm, shallow inland waters of the Late Cretaceous epoch. Mosasaurs were so well adapted to their surroundings that, unlike sea turtles, they most likely gave birth to live offspring rather than returning to the beach to lay eggs.

Dallasaurus turneri was the smallest known mosasaur, measuring less than 1 m (3.3 ft) in length. Mosasaurs of greater size were more common, with numerous species reaching lengths of more than 4 metres (13 ft). Mosasaurus hoffmannii, the largest mosasaur species are known, could have grown to be 17 metres (56 feet) long. At the Canadian Fossil Discovery Centre in Morden, Manitoba, the world's largest publicly exhibited mosasaur skeleton is now on display. The specimen, dubbed "Bruce," is just over 13 metres (43 feet) in length.

Mosasaurs had a body shape that was similar to modern monitor lizards (varanids), but it was more elongated and streamlined for swimming. Their paddles were produced by webbing between their long finger and toe bones, and their limb bones were decreased in length. Their locomotive force came from their wide tails. Mosasaurs were once thought to have swum in a manner similar to that of conger eels and sea snakes today, undulating their entire bodies from side to side.

New evidence reveals, however, that many advanced mosasaurs had huge, crescent-shaped flukes on the ends of their tails, akin to sharks and some ichthyosaurs. Rather than using snake-like undulations to reduce drag through the water, their bodies stayed firm, but their tails produced strong propulsion. Rather than pursuing after prey, these creatures may have hidden and attacked quickly and fiercely on passing prey.

Based on erroneous tracheal cartilage fragments, early reconstructions portrayed mosasaurs with dorsal crests running the length of their bodies. By the time this inaccuracy was uncovered, it had already become fashionable to show mosasaurs with similar crests in the artwork.

Giant Mosasaur

Mosasaurs were one of the late Cretaceous period's success stories. Hainosaurus is the largest known mosasaur, with a potential length of 17 metres. Giant mosasaurs were the sea's top predators and were found all across the world.

They would have spent much of their day swimming slowly towards the seabed, waiting for suitable prey to attack. They ate slow-moving species like ammonites, birds, and turtles, but when the opportunity presented itself, they would also go after larger and faster food like sharks and plesiosaurs.

Mosasaurs would have followed their prey utilising the natural cover afforded by seaweed and rocks because they were not quick swimmers. The mosasaur would only go forward when the prey was within striking distance. It was nearly guaranteed death if you were trapped in a mosasaur's jaws. Despite being the top predators in the sea, huge mosasaurs were still vulnerable to attack. The spine of one mosasaur fossil displays the signs of a shark attack.

Some Common Mosasaurs in the Western Interior Seaway

1. Platecarpus

Platecarpus is a mosasaur genus that can be found across the Western Interior Seaway. It was a medium-sized mosasaur that grew to be around 15 feet long. Lindgren et al. 2010, and Takuya et al. 2012, for example, discovered and characterised a spectacular Platecarpus tympaniticus specimen. Skin imprints, cartilage, organ tissues, including retina tissue, a partial body outline, and an articulated skeleton are all preserved in this specimen. The tail is pointing down, indicating that it was most likely a fluke (like a whale but vertical instead of horizontal). This means they swam as quickly as a shark, not as slowly as an eel. 

2. Tylosaurus

Tylosaurus is undoubtedly one of the most well-known mosasaurs, as it is a popular museum centrepiece and has appeared in Jurassic Park games, comics, and the new film "Jurassic World." It was also one of the biggest mosasaurs, reaching lengths of nearly 14 metres (45 feet). During the Cretaceous, Tylosaurus was an apex predator in North America's Western Interior Seaway. This monster could eat almost anything. In the stomach contents of these enormous marine predators, smaller mosasaurs and Plesiosaurs have been discovered.

3. Clidastes

Clidastes was a mosasaur that was one of the lesser species. Despite the fact that some species were larger, the average length of this genus is only a few metres or about 10 feet. This mosasaur was also slimmer than the others, with a narrower rib cage that gave it a sleeker, eel-like appearance. It was most likely nimble and capable of chasing down smaller prey.

Colouration 

Until 2014, when Johan Lindgren of Lund University and colleagues discovered the pigment melanin in the preserved scales of a mosasaur, the colouration of mosasaurs was unknown. Mosasaurs were likely counter-shaded, with black backs and light underbellies, similar to a great white shark or a leatherback sea turtle, both of which had fossilised relatives whose colour could be identified. The findings were published in the journal Nature.

Teeth 

Mosasaurs had the thecodont dentition, which meant that the roots were firmly cemented into the jaw bone. Mosasaurs did not have permanent teeth and instead shed them on a regular basis. The resorption pit, which is located within the roots of the old tooth, is where replacement teeth emerge. This is accomplished using an eight-stage technique that is truly unique. The first stage was marked by the mineralization of a tiny tooth crown that had formed elsewhere and had now dropped into the resorption pit. The emerging crown securely fixed itself within the resorption pit and expanded in size in the third stage, eventually reaching the same size as the crown in the original tooth in the fourth stage. The growth of the replacement tooth's root was defined by stages five and six: in stage five, the root developed vertically, and in stage six, the root spread in all directions to the point where the replacement tooth was revealed and actively pushed on the original tooth. The original tooth was shed at the seventh stage, and the now-independent replacement tooth began to anchor itself into the void. The implant tooth has grown to firmly attach itself in the eighth and final stage.

Ontogeny and Growth 

Mosasaur growth is unknown because young specimens are uncommon, and many were mistaken for hesperornithine birds when they were discovered 100 years ago. However, the discovery of many juvenile and neonate-sized mosasaurs more than a century ago suggests that mosasaurs gave birth to live young and spent their early years of life out in the open ocean, rather than in sheltered nurseries or shallow water, as previously thought. It's unclear whether mosasaurs, like other sea reptiles like plesiosaurs, offered parental care. Palaeontology published a paper about the discovery of young mosasaurs.

Guinness World Records granted the museum the title of Largest Publicly Displayed Mosasaur – Bruce in late 2014. Guinness World Records published a print edition of the record in 2016.

Possible Eggs 

A big fossilised hatched egg from Antarctica from the end of the Cretaceous, around 68 million years ago, was described in a paper published in Nature in 2020. The egg is one of the largest amniote eggs ever discovered, rivalling that of the elephant bird, and it was most likely laid by a marine species due to its soft, thin, folded nature. The egg's pore structure is strikingly similar to that of modern lepidosaurs like lizards and snakes, and the discovery of mosasaur fossils nearby suggests it was a mosasaur egg. Whether the egg was deposited on land or in the sea is uncertain. The egg was identified as Antarcticoolithus bradyi, a newly discovered oospecies.

Environment 

Palaeontologists linked mosasaur taxonomic diversity and morphological disparity patterns to Upper Cretaceous sea level, sea surface temperature, and stable carbon isotope curves to see what circumstances drove their evolution. The broader patterns of taxonomic diversification and morphological disparity lead to niche differentiation in a "fishing up" scenario under the influence of "bottom-up" selective pressures. High productivity in the Late Cretaceous, driven by tectonically regulated sea levels and climatically controlled ocean stratification and nutrient delivery, was most likely the driving factor behind mosasaur evolution. Mosasaurs went extinct as their productivity plummeted at the end of the Cretaceous, coinciding with a bolide impact.

During the Cretaceous epoch, sea levels were high, producing marine transgressions in many parts of the planet and the formation of a large inland seaway in what is now North America. Mosasaur fossils have been discovered in the Netherlands, Belgium, Denmark, Portugal, Sweden, South Africa, Spain, France, Germany, Poland, the Czech Republic, Bulgaria, the United Kingdom, Russia, Ukraine, Kazakhstan, Azerbaijan, Japan, Egypt, Israel, Jordan, Syria, Turkey, Niger, Angola, Morocco, Australia, and New Zealand. Globidens timorensis is a tooth taxon found on the island of Timor; however, its phylogenetic position is unknown, and it may not even be a mosasaur.

Distribution

Despite the fact that no single genus or subfamily is widespread around the planet, the Mosasauridae as a whole attained global distribution during the Late Cretaceous, with many localities having complex mosasaur faunas containing many genera and species in various ecological niches. Morocco and Angola are two African countries where mosasaurs are abundant.

Discovery 

The finding of a partial fossil mosasaur head in a subterranean gallery of a limestone quarry on Mount Saint Peter, near Maastricht, by quarry employees in 1764 before any notable dinosaur fossil discoveries but remained little recognized. The discovery of a partial skull, on the other hand, alerted the Age of Enlightenment to the existence of petrified animals that were unlike any known living organisms. The finding of a partial fossil mosasaur head in a subterranean gallery of a limestone quarry on Mount Saint Peter, near Maastricht, by quarry employees in 1764 before any notable dinosaur fossil discoveries but remained little recognized. The discovery of a partial skull, on the other hand, alerted the Age of Enlightenment to the existence of petrified animals that were unlike any known living organisms.

When the French revolutionary forces captured Maastricht in 1794, the carefully hidden fossil was unearthed and carried to Paris, allegedly for a prize of 600 bottles of wine. The Dutch scientist Adriaan Gilles Camper was the first to recognise its lizard connections in 1799 after it had previously been misinterpreted as a fish, a crocodile, and a sperm whale. Although the Grand Animal fossile de Mastricht was not termed Mosasaurus ('Meuse reptile') until 1822 and given its full species name, Mosasaurus hoffmannii, until 1829, Georges Cuvier validated this finding in 1808. Several pairs of mosasaur remain, discovered previously at Maastricht but not identified as mosasaurs until the 19th century, have been on exhibit at Haarlem's Teylers Museum since 1790.

The mosasaur discovery made the Maastricht limestone layers so well-known that the Cretaceous' final six-million-year period, the Maastrichtian, was named after them.

Some of the Other Marine Reptiles of the Cretaceous

Mosasaurs are known as the Cretaceous' Great Marine Reptiles. Before the mosasaurs, there were a variety of different sea reptiles. The dolphin-like ichthyosaurs, the long-necked plesiosaurs, and the short-necked pliosaurs are among the large marine reptiles that predate mosasaurs. 

Interesting Facts About Mosasaur

• Mosasaurus is one of the hundreds of genera, or groups of species, that comprise the mosasaurs, a varied family of marine reptiles.

• "MOE-zah-SORE-usis" is how Mosasaurus is pronounced.

• The Mosasaurus belonged to the aquatic squamates, a group of Mosasaurs.

• The Mosasaurus belongs to the Mosasauridae family of dinosaurs.

• Mosasaurus existed between 66 and 70 million years ago, during the Late Cretaceous Period.

• Mosasaurus specimens as large as 56 feet long have been unearthed.

• The Mosasaurus was longer than the terrifying Tyrannosaurus rex.

• Mosasaurus was an aquatic carnivore that preyed on fish, marine reptiles, birds, pterosaurs, smaller mosasaurs, and possibly even land dinosaurs.

• Mosasaurus teeth were formed like sharp spikes, letting it grab and hold onto its prey.

• The Mosasaurus's double-hinged mouth would allow it to devour its prey entirely.

• One of the last of the mosasaurids, the Mosasaurus, is thought to have existed.

• One of the largest mosasaurids, the Mosasaurus, is thought to have existed.

• Because it breathed air in a similar way to modern whales, the Mosasaurus spent most of its time near the ocean's surface.

• Instead of depositing eggs, palaeontologists believe the Mosasaurus had live births, similar to whales.

• During the Late Cretaceous Period, Mosasaurus could be found in waters all around the world.

• The Mosasaurus is thought to have existed in the oceans surrounding North America and Western Europe. They may have also lived in the oceans surrounding Japan and New Zealand.

Mosasaurs have long, slender bodies. They have evolved flippers for limbs and legs. Their jaws have a lot of conical teeth. These teeth aren't made for cutting; instead, they're made for grabbing. Their jaws are also double-hinged, allowing them to open wide and swallow prey completely, much like a snake. Mosasaurs also had scaly skin, similar to snakes, as evidenced by fossil skin imprints.