A new mosasaur species discovered in Hungary is the first known example of this group of scaled reptiles¹（爬行动物） to have lived in freshwater river environments similar to modern freshwater dolphins, according to research published December 19 in the open-access journal PLOS ONE by Laszlo Makadi from the Hungarian Natural History Museum, Hungary and colleagues from the University of Alberta, Canada and MTA-ELTE Lendület Dinosaur² Research Group, Hungary. The species lived about 84 million years ago, the largest specimens⁴ reached about 20 feet in length, and belongs to a family called 'mosasaurs（沧龙）', conventionally thought of as gigantic finned⁵ marine⁶ lizards⁷, similar and perhaps even related to present day monitor lizards. The researchers discovered several fossils of the new species, ranging from small juveniles⁹ to large adults that suggest that this species had limbs like a terrestrial lizard⁸, a flattened¹⁰, crocodile-like skull¹¹, and a tail unlike other known members of the mosasaur family.

 

The fossils were recovered from an open-pit mine in the Bakony Hills of Western Hungary, which were once flood-plains. According to the study, this is the first known mosasaur that lived in freshwater, and only the second specimen³ of a mosasaur to have been found in rocks that were not once deposited in the ocean. Makadi says, "The evidence we provide here makes it clear that similar to some lineages of cetaceans（鲸目动物）, mosasaurs quickly adapted to a variety of aquatic¹²（水生的） environments, with some groups re- invading available niches¹³ in freshwater habitats. The size of Pannoniasaurus makes it the largest known predator¹⁴ in the waters of this paleo-environment."

 

Even in the modern world, scaly¹⁵ reptiles in the aquatic world are extremely rare. Only a few species live in the water, and even fewer, like marine iguanas¹⁶ and sea kraits, live in the oceans. The new species described here probably adapted to freshwater environments similarly to river dolphins, such as those now inhabiting the Amazon, Ganges and Yangtze rivers.

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