Scientists Discover First Freshwater Mosasaur

An international team of paleontologists has described a new species of mosasaur that lived in freshwater environments about 84 million years ago.

According to scientists, the newly discovered species Pannoniasaurus inexpectatus is the first mosasaur to have lived in freshwater environments. This picture shows another species of mosasaur – Aigialosaurus bucchichi. The inset shows fossils of Pannoniasaurus inexpectatus found in Hungary, scale bar is 1 cm (Michael B.H. / CC BY-SA 3.0 / Makádi L et al)

Until now mosasaurs, large extinct reptiles, were only thought to have lived in ancient seas and oceans. But according to a new study published in the journal PLoS-ONE, the new mosasaur species from Hungary is the first known example of this group to have lived in freshwater river environments similar to modern freshwater dolphins.

The team found several fossils of the new species, ranging from small juveniles to large adults that suggest that this species had limbs like a terrestrial lizard, a flattened, crocodile-like skull, 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

The newly discovered species, named Pannoniasaurus inexpectatus, is only the second specimen of a mosasaur to have been found in rocks that were not once deposited in the ocean.

“The evidence we provide here makes it clear that similar to some lineages of cetaceans, mosasaurs quickly adapted to a variety of aquatic environments, with some groups re- invading available niches in freshwater habitats,” said lead author Dr Laszlo Makadi of the Hungarian Natural History Museum.

“The size of Pannoniasaurus makes it the largest known predator in the waters of this paleo-environment,” he said.

“Even in the modern world, scaly reptiles in the aquatic world are extremely rare. Only a few species live in the water, and even fewer, like marine iguanas 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.”


Bibliographic information: Makádi L, Caldwell MW, Ősi A. 2012. The First Freshwater Mosasauroid (Upper Cretaceous, Hungary) and a New Clade of Basal Mosasauroids. PLoS ONE 7 (12): e51781; doi: 10.1371/journal.pone.0051781