Neosauropterygia

Neosauropterygia is an extinct clade of marine reptiles that lived during the Triassic and Jurassic periods. This group is part of the larger sauropterygian order, which also includes the more primitive placodonts and pachypleurosaurids. Neosauropterygians are characterized by their paddle-like limbs, adaptations for a marine lifestyle, and typically long necks. They ranged in size from relatively small, otter-like creatures to much larger, more elongated forms.

The most well-known members of Neosauropterygia are the plesiosaurs and their sub-group, the pliosaurs. Plesiosaurs are generally recognized by their long necks and small heads, while pliosaurs had shorter necks and larger heads, often armed with formidable teeth. These reptiles were widespread in the world's oceans during the Mesozoic Era, occupying a variety of ecological niches from filter feeders to powerful predators. Their fossil record is extensive, providing valuable insights into the evolution of marine vertebrates. The precise phylogenetic relationships within Neosauropterygia are still a subject of ongoing research, but their distinct adaptations and evolutionary success highlight their importance in the history of marine life.