In this magical world, rocks that are the same age somehow date differently based on hydrological sorting.
The dinosaurs, even the itty bitty little ones get deposited first, while the pigeons and camels float above waiting their turn.
Weirdly the humans were the very last, even though one might think the mesosaurs, who swam in the ocean for a living, would be the last. Instead, they were deposited much deeper.
But you can't argue with magic.