All large Mesozoic animals were dinosaurs

The Mesozoic Era hosted diverse animal groups beyond dinosaurs. Pterosaurs were flying reptiles, plesiosaurs were marine sauropterygians, mosasaurs were marine squamates, ichthyosaurs were marine reptiles, and mammals also thrived (though remaining small). Additionally, Mesozoic oceans and skies contained numerous other lineages. Only members of the clade Dinosauria (including both non-avian dinosaurs and modern birds) are technically dinosaurs. This common conflation results from 'Mesozoic' being colloquially called 'The Age of Dinosaurs,' but multiple major reptile lineages coexisted throughout the era.