Cainozoic vs Cenozoic?
It appears to be a variant and original term for Cenozoic derived from a Greek kainos meaning “new, fresh, recent, novel".
The name "Cenozoic" (originally: "Kainozoic") was proposed in 1840 by the British geologist John Phillips (1800–1874). (Wikipedia).
We observe that Lyell, in his geological works, even the most recent, uses the word Cainozoic instead of Coenozoic or Cenozoic. Why the propounder of the terms Eocene, Miocene, etc., should thus spell the word is incomprehensible. If he is right in it, then to be consistent he ought to say Eocain, Miocain, Pliocain, Post-pliocain; for all have the same root καινός. [American Journal of Sciences and Arts, 1873]
(Etymonline)