When the plesiosaur died?

PlesiOSaurs, a group of marine reptiles that lived during the Mesozoic Era, went extinct approximately 66 million years ago at the end of the Cretaceous period. This mass extinction event is widely believed to have been caused by a combination of factors, including a catastrophic asteroid impact and extensive volcanic activity, which led to dramatic changes in the Earth's climate and ecosystems. As a result, many species, including plesiOSaurs, could not survive the harsh environmental shifts.