Name: Pannoniasaurus ‭(‬Hungarian lizard‭)‬.
Phonetic: Pan-no-ne-ah-sore-us.
Named By: L.‭ ‬Makádi,‭ ‬M.‭ ‬W.‭ ‬Caldwell‭ & ‬A.‭ ‬Osi‭ ‬-‭ ‬2012.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Squamata,‭ ‬Mosasauridae,‭ ‬Russellosaurina,‭ ‬Tethysaurinae.
Species: P.‭ ‬inexpectatus‭ (‬type‭)‬.
Diet: Carnivore/Piscivore.
Size: Roughly about‭ ‬6‭ ‬meters long.
Known locations: Hungary‭ ‬-‭ ‬Csehbánya Formation.
Time period: Santonian of the Cretaceous.
Fossil representation: Almost complete skull and post cranial skeleton.

       The holotype specimen of Pannoniasaurus was first discovered in‭ ‬1999,‭ ‬and finally described to science as a new genus of mosasaur in‭ ‬2012.‭ ‬This description made history in the field of mosasaur research as it marked the first time that a mosasaur had been found in a freshwater deposit.‭ ‬Before this discovery,‭ ‬mosasaurs had only ever been found in marine‭ (‬salt water‭) ‬deposits.
       This discovery confirmed an idea that many people had already had about mosasaurs.‭ ‬Being reptiles,‭ ‬they were air breathers with lungs,‭ ‬and not gills like fish,‭ ‬and so moving from salt to freshwater should have offered no problems in terms of respiration.‭ ‬The only real difference between fresh and salt water is that fresh water does not offer as much buoyancy as salt water,‭ ‬so a Pannoniasaurus‭ (‬and other marine reptile‭) ‬in freshwater may have had to expend a little more energy in swimming and reaching the surface.
       The Pannoniasaurus holotype was found in an area that during the late Cretaceous was a river basin,‭ ‬and while this confirms that this individual Pannoniasaurus was in freshwater at the time of its death,‭ ‬it does not necessarily mean that this genus of mosasaur was restricted to this river system.‭ ‬This individual may have been an occasional visitor,‭ ‬or attracted upstream by the smell of a carcass of a dinosaur that had drowned upstream,‭ ‬or perhaps have been washed into the river by a storm surge,‭ ‬we simply do not know yet how.‭ ‬It is still quite probable however that Pannoniasaurus could have also ventured into the sea,‭ ‬perhaps hopping along coastlines from one river system to the next.‭ ‬This is not that farfetched an idea,‭ ‬in modern times the saltwater crocodile‭ (‬Crocodylus porosus‭) ‬is documented as venturing cross Southeast Asia,‭ ‬swimming across hundreds of miles of open sea to reach new hunting grounds.

Further reading
-‭ ‬The first freshwater mosasauroid‭ (‬Upper Cretaceous,‭ ‬Hungary‭) ‬and a new clade of basal mosasauroids.‭ ‬-‭ ‬PLoS ONE‭ ‬7‭(‬12‭)‬:e51781.‭ ‬-‭ ‬L.‭ ‬Makádi,‭ ‬M.‭ ‬W.‭ ‬Caldwell‭ & ‬A.‭ ‬Osi‭ ‬-‭ ‬2012.


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