Nothosaurs were 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...

 marine 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...

s that may have lived like seals

Pinniped

Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

 of today, catching food in water but coming ashore on rocks and beaches. They averaged about 3 metres (9.8 ft) in length, with a long body and tail. The feet were paddle-like, and are known to have been webbed in life, to help power the animal when swimming. The neck was quite long, and the head was elongate and flattened, and relatively small in relation to the body. The margins of the long jaws were equipped with numerous sharp outward-pointing teeth, indicating a diet of fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 and squid

Squid

Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

.

Taxonomy

The nothosaurs consist of two suborders:

• 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...
  
  ia, small primitive forms, and
• Nothosauria, (including Ceresiosaurus
  Ceresiosaurus
  Ceresiosaurus, meaning "Lizard of Ceresio" , is an extinct genus of aquatic sauropterygian reptile belonging to the nothosaur order...
  
  , 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...
  
  , and Nothosaurus
  Nothosaurus
  Nothosaurus is an extinct genus of sauropterygian reptile from the Triassic period, approximately 240-210 million years ago, with fossils being distributed from North Africa and Europe to China...
  
  ), which evolved from pachypleurosaurs.

Nothosaur-like reptiles were in turn ancestral to the more completely marine plesiosaur

Plesiosaur

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

s, which replaced them at the end of the Triassic period.