`This needs extensive editing, both for grammar (e.g., ``One of which`` should not be a new sentence) and for technical accuracy.  It would be useful to identify more of the forms which became extinct at this time  off the top of my head, the champsosaurs, sebecosuchids, multituberculates, dinocerates, most creodonts, numerous other mammal families and orders.  Archaeoceti is not a ``subgenus`` but a suborder.  The tag should not be Archaeology but Paleontology or Historical geology. `