Movie is called The Land before Time Critique.

What geologic era is this movie based upon?

The Land Before Time suggests that the series takes place at the end of the Mesozoic Era

The Great Valley is said to be the most beautiful and perfect place in all the leaf-eater dinosaurs world. Littlefoot's reaching it is the goal of the first film and it has been his home and the home of his friends ever since. Littlefoot and Spike would have lived during the Late Jurassic period, which spanned from around 165 to 145 million years ago, while many of the others would have actually lived during the Late Cretaceous period, which spanned from around 100 to 66 million years ago.

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