This needs extensive editing both for grammar eg 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