The first specimen with skin preserved of Lariosaurus (Eusauropterygia) from the Middle Triassic of Monte San Giorgio (Switzerland) allows inferences about its swimming method

Abstract

A new virtually complete specimen of the eosauropterygian nothosauroid Lariosaurus valceresii is described. The specimen was collected in the Kalkschieferzone of the Meride Limestone (Ladinian, Middle Triassic) in the UNESCO World Heritage area of Monte San Giorgio (Switzerland/Italy). The new specimen is the first L. valceresii collected in Switzerland and the first known Lariosaurus specimen with remains of the skin. The skin is preserved as a carbon film revealing the shape of the scales. It outlines the body and limbs, showing that the hands and feet were webbed. The skin is present postaxial to both the humeral shafts and the anterior portion of the trunk suggesting the possible presence in life of large and very strong retractor muscles for the forelimbs indicative that Lariosaurus could have performed a paraxial, otariid-like, "flying-rowing" swimming for rapid acceleration.