A fossil discovered in Hungary is providing the first evidence that there were mosasaur species that lived in freshwater. Mosasaurs were scaled reptiles that lived in marine environments, and apparently also in freshwater rivers as the new fossil shows.
“The species lived about 84 million years ago, the largest specimens reached about 20 feet in length, and belongs to a family called ‘mosasaurs’, conventionally thought of as gigantic finned marine lizards, similar and perhaps even related to present day monitor lizards. The researchers discovered 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 fossil was found in an open-pit mine located in the Bakony Hills of Western Hungary. This area was once flood plains. “This is the first fossil evidence to suggest that mosasaurs lived in freshwater, and 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. The size of Pannoniasaurus makes it the largest known predator in the waters of this paleo-environment.”
“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.”
The research was just published December 19th in the open-access journal PLOS ONE.
Source: Public Library of Science
Image Credits: Makadi L, Caldwell MW, Osi 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