mezozoic
Webster's Dictionary (GCIDE)
Reptilian \Rep*til"i*an\ (-an), a. Belonging to the reptiles. [1913 Webster]
Reptilian age (Geol.), that part of geological time comprising the Triassic, Jurassic, and Cretaceous periods, and distinguished as that era in which the class of reptiles attained its highest expansion; -- called also the Secondary or Mezozoic age. [1913 Webster]