Name: Russellosaurus ‭(‬Russel’s lizard‭)‬.
Phonetic: Rus-sal-oh-sore-us.
Named By: M.‭ ‬J.‭ ‬Polcyn‭ & ‬G.‭ ‬L.‭ ‬Bell Jr‭ ‬-‭ ‬2005.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Squamata,‭ ‬Mosasauridae,‭ ‬Russellosaurinae.
Species: R.‭ ‬coheni‭ (‬type‭)‬.
Diet: Carnivore.
Size: Uncertain.
Known locations: USA,‭ ‬Texas‭ ‬-‭ ‬Arcadia Park Shale and Kamp Ranch Limestone.
Time period: Turonian of the Cretaceous.
Fossil representation: Skull as well as additional fragmentary remains.

       Russellosaurus represents a primitive mosasaur,‭ ‬marine reptiles that would go on to achieve a variety of sizes and specialisations that would see them becoming the dominant predators of the late Cretaceous seas.‭ ‬Russelosaurus itself displays a number of features which are diagnostic of more than one mosasaur group,‭ ‬something that suggests that these traits were developed and lost according to the predatory niche that a specific group or genera became accustomed too.‭ ‬As for Russellosaurus it was probably a more generalist carnivore that preyed upon fish and other smaller marine vertebrates.‭
       Russellosaurus is considered to be related to Yaguarasaurus and Tethysaurus,‭ ‬both primitive mosasaurs in their own rights that are known from deposits in South America and Africa respectively.‭ ‬This shows that while early mosasaurs where more primitive in form,‭ ‬they were still well enough adapted to marine life to spread out across‭ ‬the ocean.‭ ‬None of these mosasaurs are considered to be the earliest however,‭ ‬as in‭ ‬2005‭ ‬Polcyn and Bell also named another even more primitive form called Dallasaurus.‭

Further reading
- Russellosaurus coheni n. gen., n. sp., a 92 million-year-old mosasaur from Texas (USA), and the definition of the parafamily Russellosaurina. - Netherlands Journal of Geosciences — - Geologie en Mijnbouw 84(3):321-333. - M. J. Polcyn & G. L. Bell - 2005.


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