Possible Clues:

• Period of the first dinosaurs
• Terrible crisis at time dinosaurs appeared
• First period of the Mesozoic Era
• The stair gets broken like this for an age
• Time sorted out a crisis related to old age
• Time between Permian and Jurassic; at crisis (anag.)
• Secondary system's spasm circumscribes Scripture simpleton
• By the sound of it, try and get silly, I see, for an age
• Of the period when dinosaurs first appeared
• It came between Permian and Jurassic