Ancient giant salamanders lived on land and water unlike their modern day counterparts, finds a new study.

Researchers from University of Tübingen, Germany, studied the fossil remains of the oldest known giant salamander, aviturus exsecratus, collected from the northwestern Gobi Desert in southern Mongolia.

Giant salamanders are the largest living amphibians. While one of the species is found in the United States, the Asian species are more commonly found in Japan and China. These giant species can grow up to 6 feet (2 meters) long and can live up to 100 years.

Most of the fossil remains of their ancestors are found in Eurasia. By studying the 56-million-year-old specimens of the ancient salamanders, researchers were able to determine certain features of the amphibian.

Earlier studies have shown that the ancient salamanders had almost similar lifestyles as that of the modern salamanders. However, the modern ones prefer to live in fast-flowing mountain streams with high oxygen content whereas the fossil remains of the ancient salamanders were found in rocks formed from water's-edge sediments. This suggested that the ancient amphibian lived in rivers and lakes in lowlands.

Now, the research team has found another difference in the salamanders that they hunted for prey on the land and in the water, which is not known among the modern day salamanders that live only in water.

Examining the shape of the fossil's lower jaw, researchers concluded that they fed on fish and other invertebrates in the water and also preyed on insects. The fossil had the longest limbs and strong bones that helped them to move on land. They also had a well-developed sense of smell and their palate bone was stronger showing more evidence that the ancient salamanders were also terrestrial animals.

Experts pointed out that the development in the aviturus exsecratus first occurred during the Paleocene-Eocene Thermal Maximum, a short period of global warming that occurred 55.8 million years ago when the global temperatures saw a rise of 10 degrees Fahrenheit (6 degrees Celsius) after the extinction of the dinosaurs.

They noted that giant salamanders first appeared as a terrestrial animal during the warm period, but as the temperatures cooled, they stayed in the water and did not further develop or venture out on land, becoming an aquatic creature, according to a report in LiveScience 

The findings of the study, "Pronounced Peramorphosis in Lissamphibians-Aviturus exsecratus (Urodela, Cryptobranchidae) from thePaleocene-Eocene Thermal Maximum of Mongolia", are published in the journal PLOS ONE.