Final answer:
The split between nodosaurids and ankylosaurids occurred by the Cretaceous period, which followed the Jurassic, the 'Golden Age of Dinosaurs'.
Step-by-step explanation:
The evolutionary split between nodosaurids and ankylosaurids is believed to have taken place by the Cretaceous period. This period saw many significant events in dinosaur evolution, including the flourishing of dinosaurs during the Jurassic, which was known as the 'Golden Age of Dinosaurs', followed by the emergence of new species and families in the Cretaceous, as evidenced by the diversity of dinosaurs, including the appearance of nodosaurids and ankylosaurids. The diversity of dinosaurs continued until the mass extinction event at the end of the Cretaceous.