Polycotylids have been traditionally classified as pliosaurs because of their short necks and relatively large heads. However, cladistic analyses that take into account a broader suite of anatomical characters have revealed that they are probably plesiosauroids, and therefore more closely related to the long-necked elasmosaurids and cryptoclidids than to pliosaurs.

All polycotylids share a number of features including an elongate rostrum and short postorbital region. They had a worldwide distribution in the Cretaceous Period.

Polycotylid genera

  • Brancasaurus (according to Ketchum and Benson, 2011)
  • Dolichorhynchops
  • Edgarosaurus
  • Eopolycotylus
  • Georgiasaurus
  • Umoonasaurus
  • Pahasapasaurus
  • Palmulina
  • Polycotylus
  • Sulcusuchus
  • Thililua
  • Trinacromerum