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Re: Extinction Question and a Thank You!

T. Michael Keesey wrote:

closest common ancestor of all crocodylians which survived the end of
the Mesozoic appeared during the Cretaceous, as did the closest common
ancestor of all Cenozoic sharks, if I am not mistaken.

The most recent common ancestor of modern sharks (Neoselachii) probably first appeared in the Triassic or Jurassic. But many modern shark orders and families do not make an appearance in the fossil record until the Cretaceous.