User:Macrophyseter/sandbox10
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A mosasaur (from Latin Mosa meaning the 'Meuse', and Greek σαύρος sauros meaning 'lizard'), strictly speaking,[lower-alpha 1] is an extinct aquatic lizard with paddle-like limbs within the family Mosasauridae that lived during the Late Cretaceous Period. They also have a long streamlined body with a tail that ends in a downward bend and supports a fin-like fluke on top. Nearly all mosasaurs were wholly marine, though freshwater incursions also occurred. Mosasaur genera belong to one of three mosasauroid groups: the subfamilies Mosasaurinae and Halisaurinae, and the clade Russellosaurina. Mosasaurs evolved from a group of extinct semiaquatic lizards with terrestrial limbs called aigialosaurs during the Turonian (93.9-89.8 mya), mirroring the later evolution of whales from their terrestrial ancestors. It was traditionally believed that all mosasaurs descended from a single origin (monophyletic) and were accordingly classified under the family Mosasauridae. However, emerging discoveries during the 21st century suggests that mosasaurs may not form a natural family, and instead actually represent at least two or three independent lineages that achieved a similar aquatic body plan through convergent evolution (polyphyletic). This multiple-origins hypothesis remains controversial due to the poor fossil record of Turonian mosasauroids.
Mosasaurs | |
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Mosasaurs, in the traditional sense, are an evolutionary grade within the family Mosasauridae | |
![]() Mounted skeleton of a russellosaurine (Plesioplatecarpus planifrons) | |
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Temporal range: Late Cretaceous, 93–66 Ma | |
Subgroups containing mosasaurs | |
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Mosasaurs were incredibly successful. The three groups collectively attained a cosmopolitan distribution encompassing nearly all latitudes, including polar regions. They were dominant predators in nearly all marine ecosystems, becoming ubiquitous features of Late Cretaceous oceans. Mosasaurs appeared during a period of high global primary productivity sparked by warm oceans and the aftermath of the Cenomanian-Turonian boundary event, and of opened ecological niches following the extinctions of the ichthyosaurs and pliosaurs, which may have supported their rapid worldwide radiation. Within a span of ~30 million years, they diversified into at least 80 unique species and occupied a wide variety of carnivorous niches. The smallest mosasaurs measured about 2 meters (6.6 ft) long, while the largest were apex predators that grew in excess of 14 meters (46 ft). Mosasaurs achieved their peak in diversity towards the very end of the Cretaceous until their sudden extinction during the Cretaceous-Paleogene extinction event 66 mya.
Mosasaurs were the earliest fossil reptiles to be recognized by scientists. The first known remains, belonging to the eponymous Mosasaurus, were discovered in the Netherlands between the 1760s and 80s. Their identification by 1808 as a giant aquatic monitor lizard that no longer exists was key in solidifying the new concept of extinction. The Bone Wars rivalry between American paleontologists Edward Drinker Cope and Othniel Charles Marsh during the late 1800s sparked an explosion of mosasaur research in the United States. Most of the iconic genera were described in this period, and scientific understanding of mosasaur anatomy was perfected by the 1890s. The Bone Wars discoveries also gave rise to the hypothesis that mosasaurs were not monitor lizards but instead close relatives of snakes united under the clade Pythonomorpha. Scientist debate to this day whether mosasaurs are most closely related to monitor lizards or snakes.