Ceresiosaurus, meaning "Lizard of Ceresio" (Ceresio is the name of the Lake Lugano

Lake Lugano

Lake Lugano is a glacial lake in the south-east of Switzerland, at the border between Switzerland and Italy. The lake, named after the city of Lugano, is situated between Lake Como and Lago Maggiore...

, in Switzerland

Switzerland

Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

), is an extinct genus of aquatic sauropterygia

Sauropterygia

Sauropterygia were a group of very successful aquatic reptiles that flourished during the Mesozoic before they became extinct at the end of the era. They were united by a radical adaptation of their shoulder, designed to support powerful flipper strokes...

n reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

 belonging to the nothosaur

Nothosaur

Nothosaurs were Triassic marine sauropterygian reptiles that may have lived like seals of today, catching food in water but coming ashore on rocks and beaches. They averaged about in length, with a long body and tail. The feet were paddle-like, and are known to have been webbed in life, to help...

 order. Its fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s have been found in Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, and was named by Bernhard Peyer in 1931.

Ceresiosaurus lived during the Anisian

Anisian

In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 245 million years ago until 237 million years ago, approximately...

 stage of the middle Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

.

Olivier Rieppel suggested that Ceresiosaurus is a synonym of Lariosaurus

Lariosaurus

Lariosaurus is an extinct genus of nothosaur from the Triassic period of northern Italy. With a length of just , it was one of the smallest known nothosaurs...

.

Palaeobiology

Ceresiosaurus was much more elongated than its relatives, reaching 4 metres (13.1 ft) in length, and had fully developed flippers with no trace of visible toes. It had multiple elongated phalanges, making the flippers much longer than in most other nothosaurs, and more closely resembling those of the later plesiosaur

Plesiosaur

Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...

s. Ceresiosaurus also had the shortest skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

 of any known nothosaur, which further increased its resemblance to plesiosaurs.

Although possessing a long neck and tail, Ceresiosaurus may not have swum by undulating

Undulation

Undulation may refer to:* Lateral undulation, the most primitive of vertebrate locomotor patterns* Law of Undulation, an invention of C. S. Lewis* Undulation of the geoid, the separation between the geoid and the reference ellipsoid of the Earth...

 its body. Analysis of the bone structure of the hips and powerful tail suggest that it instead propelled itself through the water much like a penguin

Penguin

Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...

. The evidence of pachypleurosaur

Pachypleurosaur

Pachypleurosaurs were primitive sauropterygian reptiles that vaguely resembled aquatic lizards, and were limited to the Triassic period. They were elongate animals, ranging in size from 20 cm to about a meter in length, with small heads, long necks, paddle-like limbs, and long deep tails. The...

s in the preserved stomach of Ceresiosaurus remains lend credence to the theory of it being a fast swimmer.