Elasmosauridae


Classification

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Elasmosauridae

The Elasmosauridae sre characteristically very long-necked plesiosaurs. They form a major component of Late Cretaceous plesiosaur assemblages.
The definition of Elasmosauridae has changed in recent years as our understanding of plesiosaur evolution has improved.
Older definitions included many Jurassic long-necked forms (Bardet et al. 1999; Cruickshank et al. 2002). However, today Elasmosauridae has a more restricted
definition and contains exclusively Cretaceous taxa. Synapomorphies (shared derived characters) of the clade Elasmosauridae include (Bardet et al. 1999):

  • Ventral cheek margin weakly excavated
  • Pterygoids on palate closed anteriorly (lacks anterior pterygoid vacuity)
  • Platycoelus (flat articulation surfaces) to the vertebrae
  • Greater than 40 cervical vertebrae
  • cervical centrum length greater than height
  • Anterior cervical vertebrae with lateral keel

Elasmosaurid genera

Several elasmosaurid genera are considered nomina dubia or are regarded as junior synonyms of other genera. The following names are therefore invalid :

  • ‘Woolungasaurus’ = Elasmosauridae indet.
  • ‘Alzadasaurus’ = ?
  • Aprosaurus ?
  • Ogmodirus ?
  • Fresnosaurus ?