This timeline of mosasaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, and taxonomic revisions of mosasaurs, a group of giant marine lizards that lived during the Late Cretaceous Epoch. Although mosasaurs went extinct millions of years before humans evolved, humans have coexisted with mosasaur fossils for millennia. Before the development of paleontology as a formal science, these remains would have been interpreted through a mythological lens. Myths about warfare between serpentine water monsters and aerial thunderbirds told by the Native Americans of the modern western United States may have been influenced by observations of mosasaur fossils and their co-occurrence with creatures like Pteranodon and Hesperornis . [1]
The scientific study of mosasaurs began in the late 18th century with the serendipitous discovery of a large fossilized skeleton in a limestone mine near Maastricht in the Netherlands. [2] The fossils were studied by local scholar Adriaan Gilles Camper, who noted a resemblance to modern monitor lizards in correspondence with renowned French anatomist Georges Cuvier. [3] Nevertheless, the animal was not scientifically described until the English Reverend William Daniel Conybeare named it Mosasaurus , after the river Meuse located near the site of its discovery. [4]
By this time the first mosasaur fossils from the United States were discovered by the Lewis and Clark Expedition, and the first remains in the country to be scientifically described were reported slightly later from New Jersey. [5] This was followed by an avalanche of discoveries by the feuding Bone War paleontologists Edward Drinker Cope and Othniel Charles Marsh in the Smoky Hill Chalk of Kansas. [6] By the end of the century a specimen of Tylosaurus would be found that preserved its scaley skin. [7] Later Samuel Wendell Williston mistook fossilized tracheal rings for the remains of a fringe of skin running down the animal's back, which subsequently became a common inaccuracy in artistic restorations. [8]
The 20th century soon saw the discovery in Alabama of a strange mosasaur called Globidens , with rounded teeth suited to crushing shells. [9] Mosasaur remains were also discovered in Africa and California. [10] In 1967 Dale Russell published a scientific monograph dedicated to mosasaurs. [11] Embryonic remains in the 1990s confirmed that mosasaurs gave live birth like in ichthyosaurs. [12] The 1990s also saw a revival and escalation of a debate regarding whether or not some supposed mosasaur toothmarks in ammonoid shells were actually made by limpets. [13] By the end of the century, the evolutionary relationship between mosasaurs and snakes as well as the possible involvement of mosasaurs in the extinction of the aforementioned ichthyosaurs became hot button controversies. [14]
The debates regarding snakes, toothmarks, and ichthyosaurs spilled over into the early 21st century. These discussions were also accompanied by the discovery of many new taxa, including new species of Globidens, Mosasaurus, and Tylosaurus as well as entirely new genera like Yaguarasaurus and Tethysaurus . [15] In 2013, Lindgren, Kaddumi, and Polcyn reported the discovery of a Prognathodon specimen from Jordan that preserved the soft tissues of its scaley skin, flippers and tail. Significantly, the tail resembled those of modern carcharinid sharks, although the bottom lobe of the tail fin was longest in the mosasaur whereas shark tails have longer upper lobes. [16]
The Cheyenne believe that there were many different kinds of water monsters that lived not only in lakes, rivers, and springs but also high bluffs and hills. The locations given as water monster habitat are similar to the locations where local marine fossils can be found as fossils often erode out of hillsides or stream banks. The Cheyennes feared the water monsters, because they could be dangerous predators or capsize their canoes. Even in modern times, tradition-minded Cheyenne sometimes take pains to avoid sleeping too close to springs due to fears of water monsters. [21]
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Williston also discussed mosasaur life appearance and behavior. He compared mosasaur scales to those of monitor lizards and misinterpreted some fossilized cartilage as evidence for a fringe of soft tissue down mosasaurs' backs. [50] He hypothesized that mosasaurs left the safety of the water to lay eggs on land. [51] The paleobiology of individual mosasaur taxa also received Williston's attention. He thought the genus Clidastes as an inhabitant of near-surface waters. [52] In contrast, Williston interpreted Platecarpus as a "deep diver" and thought Tylosaurus fed primarily on other marine reptiles. [53]
He also elaborated on his earlier research into mosasaur biostratigraphy. He observed that Tylosaurus ranged throughout the Smoky Hill Chalk but went extinct around the time the Fort Pierre Shale was deposited. Platecarpus was also only known from the Niobrara Formation. Clidastes was only known from the upper Niobrara. [54]
Dale Russell published a monograph on American mosasaurs. [11] This monograph contained significant taxonomic revisions for the family. Among these were his conclusion that Platecarpus coryphaeus and Platecarpus ictericus were likely junior synonyms of P. tympaniticus while P. planfirons was too poorly preserved to be classified confidently at all. [73] Russell also dismissed the species Tylosaurus dyspelor described by Cope as a dubious probable-synonym of Tylosaurus proriger. [74]
Russell also published additional information and speculation on mosasaur biostratigraphy. He reported the presence of mosasaur vertebrae up to 90 million years old among the Turonian fossils curated by the University of Kansas Museum of Natural History. [75] Another of this work's significant contributions to mosasaur biostratigraphy concerned the mosasaurs of the Smoky Hill Chalk. Russell devised two biostratigraphic zones based on the Chalk's mosasaur fossils. The lower zone was characterized by Clidastes liodontus , Platecarpus coryphaeus, and Tylosaurus nepaeolicus. The upper was home to Clidastes, Platecarpus ictericus, and Tylosaurus proriger. [54] He regarded Platecarpus and Tylosaurus as deep water animals but concluded that the biostratigraphic evidence from the Smoky Hill mosasaurs suggested that the Chalk's depositional environment was becoming shallower and nearer to the ancient coastline over time. [76] Russell also argued that by the end of the Late Cretaceous, mosasaurs were converging on the body plan that characterized the first ichthyosaurs during the Triassic period and gradually replacing these older marine reptiles. [77]
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Mosasaurs comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. They belong to the order Squamata, which includes lizards and snakes.
Mosasaurus is the type genus of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages of the Late Cretaceous. The genus was one of the first Mesozoic marine reptiles known to science—the first fossils of Mosasaurus were found as skulls in a chalk quarry near the Dutch city of Maastricht in the late 18th century, and were initially thought to be the bones of crocodiles or whales. One skull discovered around 1780, which was seized by France during the French Revolutionary Wars for its scientific value, was famously nicknamed the "great animal of Maastricht". In 1808, naturalist Georges Cuvier concluded that it belonged to a giant marine lizard with similarities to monitor lizards but otherwise unlike any known living animal. This concept was revolutionary at the time and helped support the then-developing ideas of extinction. Cuvier did not designate a scientific name for the new animal, and this was done by William Daniel Conybeare in 1822 when he named it Mosasaurus in reference to its origin in fossil deposits near the Meuse River. The exact affinities of Mosasaurus as a squamate remain controversial, and scientists continue to debate whether its closest living relatives are monitor lizards or snakes.
Tylosaurus is a genus of mosasaur, a large, predatory marine reptile closely related to modern monitor lizards and to snakes, from the Late Cretaceous.
Selmasaurus is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Plioplatecarpinae subfamily alongside genera like Angolasaurus and Platecarpus. Two species are known, S. russelli and S. johnsoni; both are exclusively known from Santonian deposits in the United States.
The Tylosaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "tylosaurines" and have been recovered from every continent except for South America. The subfamily includes the genera Tylosaurus, Taniwhasaurus, Hainosaurus and Kaikaifilu, although some scientists argue that only Tylosaurus and Taniwhasaurus should be included.
The Halisaurinae are a subfamily of mosasaurs, a group of Late Cretaceous marine lizards. They were small to medium-sized, ranging from just under 3 meters in Eonatator sternbergi to as much as 8 or 9 meters in Pluridens serpentis. They tended to have relatively slender jaws and small, numerous teeth, suggesting a diet of small fish and other prey. Although the skeleton is primitive compared to other Mosasauridae in many respects, halisaurines had the distinctive hypocercal tail of other mosasaurids suggesting good swimming ability, and they persisted alongside other mosasaurs until the end of the Cretaceous. The earliest known remains of halisaurines occur in rocks of Santonian age and the subfamily persists until the latest Maastrichtian. Halisaurines are known from North and South America, Europe, Asia and Africa, indicating a more or less global distribution in the Late Cretaceous. Four genera are currently recognized: Eonatator, Halisaurus, Phosphorosaurus and Pluridens.
Eonatator is an extinct genus of marine lizard belonging to the mosasaur family. It is a close relative of Halisaurus, and part of the same subfamily, the Halisaurinae. It is known from the Late Cretaceous of North America, Colombia and Sweden. Originally, this taxon was included within Halisaurus, but was placed in its own genus, which also led to the subfamily Halisaurinae being created for the two genera.
Platecarpus is an extinct genus of aquatic lizards belonging to the mosasaur family, living around 84–81 million years ago during the middle Santonian to early Campanian, of the Late Cretaceous period. Fossils have been found in the United States and possible specimens in Belgium and Africa. A well-preserved specimen of Platecarpus shows that it fed on moderate-sized fish, and it has been hypothesized to have fed on squid, and ammonites as well. Like other mosasaurs, it was initially thought to have swum in an eel-like fashion, although another study suggests that it swam more like modern sharks. An exceptionally well-preserved specimen of P. tympaniticus known as LACM 128319 shows skin impressions, pigments around the nostrils, bronchial tubes, and the presence of a high-profile tail fluke, showing that it and other mosasaurs did not necessarily have an eel-like swimming method, but were more powerful, fast swimmers. It is held in the Natural History Museum of Los Angeles County. Isotopic analysis on teeth specimens has suggested that this genus and Clidastes may have entered freshwater occasionally, just like modern sea snakes.
Globidens is an extinct genus of mosasaurid oceanic lizard classified as part of the Globidensini tribe in the Mosasaurinae subfamily.
Prognathodon is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like Mosasaurus and Clidastes. Prognathodon has been recovered from deposits ranging in age from the Campanian to the Maastrichtian in the Middle East, Europe, New Zealand, and North America.
Halisaurus is an extinct genus of marine reptile belonging to the mosasaur family. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination of features and prompted a new genus to be described. It was named by Othniel Charles Marsh in 1869 and means "ocean lizard". It was renamed by Marsh to Baptosaurus in 1870, since he believed the name to already be preoccupied by the fish Halosaurus. According to modern rules, a difference of a letter is enough and the substitute name is unneeded, making "Baptosaurus" a junior synonym.
Pluridens is an extinct genus of marine lizard belonging to the Mosasauridae. Pluridens is placed in the subfamily Halisaurinae with the genera Phosphorosaurus, Eonatator and Halisaurus. Compared to related halisaurines, Pluridens had longer jaws with more teeth, and smaller eyes. It also grew large size, measuring 5–6 m (16–20 ft) long and perhaps over 9 m (30 ft) in some individuals. The jaws in some specimens are robust, and sometimes show injuries suggestive of combat. The jaws may have been used for fighting over mates or territories.
Goronyosaurus is an extinct genus of marine lizard belonging to the mosasaur family. Fossils of Goronyosaurus are exclusively known from the Dukamaje Formation of Niger and Nigeria and also the Rima Formation of Nigeria, and are both Maastrichtian in age. The holotype was first described in 1930 as Mosasaurus nigeriensis, but subsequent remains revealed a highly unique set of adaptations that prompted the species to be reclassified as the only species of the new genus Goronyosaurus in 1972. These unique adaptations have made Goronyosaurus notoriously difficult to classify within the Mosasauridae and it is often left out of phylogenetic analyses, although most authors agree that Goronyosaurus belonged to Mosasauridae.
Liodon is a dubious genus of mosasaur from the Late Cretaceous, known from fragmentary fossils discovered in St James' Pit, England and possibly also the Ouled Abdoun Basin of Morocco. Though dubious and of uncertain phylogenetic affinities, Liodon was historically a highly important taxon in mosasaur systematics, being one of the genera on which the family Mosasauridae was based.
Ectenosaurus is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Plioplatecarpinae subfamily alongside genera like Angolasaurus and Platecarpus. Ectenosaurus is known from the Santonian and Campanian of Kansas, Alabama, and Texas.
Angolasaurus is an extinct genus of mosasaur. Definite remains from this genus have been recovered from the Turonian and Coniacian of Angola, and possibly the Coniacian of the United States, the Turonian of Brazil, and the Maastrichtian of Niger. While at one point considered a species of Platecarpus, recent phylogenetic analyses have placed it between the (then) plioplatecarpines Ectenosaurus and Selmasaurus, maintaining a basal position within the plioplatecarpinae.
The Globidensini or Globidentatini are a tribe of mosasaurine mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the tribe, known as "globidensins" or "globidensine mosasaurs", have been recovered from North America, Europe, Africa and Asia. The tribe contains the genera Globidens, Carinodens, Igdamanosaurus, Harranasaurus and Xenodens. Features of the maxilla and digits make the placement of Carinodens and Xenodens in the tribe uncertain; some researchers have suggested that they may be more appropriately placed in the Mosasaurini.
This research history of Mosasaurus documents the historical, cultural, and scientific accounts surrounding the Mosasaurus, a genus of extinct aquatic squamate reptile that lived during the Late Cretaceous.