University of Tübingen: An Indian otter in Germany

Researchers from the Universities of Tübingen and Zaragoza have come across a previously unknown species of otter from layers 11.4 million years old at the Hammerschmiede fossil site. The excavation site in the Allgäu became known worldwide in 2019 through the discovery of the two-legged great ape Danuvius guggenmosi . The new species published in the Journal of Vertebrate Palaeontology was named Vishnuonyx neptuni , which means something like Neptune’s Vishnu otter. The genus of the Vishnu otter was previously only known from Asia and Africa.

The research team digs in the hammer forge under the direction of Professor Madelaine Böhme from the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tübingen. It has already been able to recover over 130 different species of extinct vertebrates from river deposits, which are attributed to the Ur-Günz. Many of these species are adapted to life in and around the water. The evidence of a Vishnu otter in Bavaria came unexpectedly, as its representative was previously only known from regions outside Europe.

The spread of the Vishnu otters
Every sixth species of today’s predators lives aquatic, either in the oceans such as seals or in fresh water such as the otters. The evolutionary history of the total of 13 otter species occurring today is still comparatively unexplored. Vishnu otters ( Vishnuonyx ) are predators of medium size and weighing ten to 15 kilograms, which were first known from sediments at the foot of the Himalayas. They lived in the great rivers of South Asia 14 to 12.5 million years ago.

Recent finds have shown that Vishnu otters reached East Africa about 12 million years ago. The discovery in the 11.4 million year old layers of the hammer forge has shown for the first time that they also occurred in Europe – they may have spread from India to the entire Old World. Like all otters, the Vishnu otter also depends on water; it cannot cover long distances over land. Its enormous spread of more than 6,000 kilometers across three continents was made possible by the geographic situation 12 million years ago: mountain formations from the Alps in the west to the Iranian Elbrus Mountains in the east created a large sea basin from the Tethys Ocean, the forerunner of Mediterranean and Indian Oceans, separated.

As a result, the Paratethys was formed, a huge Eurasian body of water that stretched from Vienna to beyond what is now the Aral Sea in Kazakhstan. 12 million years ago this had only a narrow connection to the Indian Ocean, the so-called Araks Strait in what is now Armenia. The researchers suspect that Neptune’s Vishnu otter followed this connection to the west and to the west of today’s city of Vienna, via the delta of the ancient Danube, southern Germany, which was then emerging, reached the ancient Günz and the hammer mill.

The teeth of the fish robbers
At the recently founded Center for Visualization, Digitization and Replication in the Geosciences Faculty of the University of Tübingen, the researchers used computer tomographic methods to make the finest details in the tooth structure of the fossils visible. This technique made it possible to observe very small structures in the otter’s teeth. The pointed humps, shear blades, and restricted grinding areas suggest a diet that was primarily fish based. From an ecological point of view, Neptune’s Vishnu otter is more similar to the Eurasian otter than the Pacific sea otter or the African and Asian finger otters – both of these groups prefer crustaceans over fish in their diet.