Big dinosaurs, it turns out, avoided the tropics for millions of years due to chaotic, unpredictable climates. Such drastic changes in the climate would have been detrimental to survival, causing the larger dinosaurs to avoid such regions for tens of millions of years. Small carnivorous dinosaurs could have been found in the tropics, but researchers discovered that the larger plant eating dinosaurs stuck to high latitudes during the Triassic period. Climate, it turns out, was to blame for such dinosaur distributions.
Researchers came to this conclusion by looking at rocks from Ghost Ranch, New Mexico, particularly with the Chinle Formation cliffs. This area is full of fossils from the aforementioned Triassic period, and quite an attractive spot for researchers studying the period.
Using the data from rocks, a detailed report of the ecology and climate from the period was assembled — everything from pollen that was present to wildfire temperatures was deduced. Together the data paints a picture of the climate at the time — one that was marked by sudden and drastic changes, resulting in plants alternating from being common in the region to rare and back again.
Wildfires would have been common at the time, according to the researchers, having happened every fifty or so years. In addition, droughts and wet seasons alternated frequently.
All of this would have made survival difficult for the plant eating dinosaurs, as plants would have had trouble growing in any significant numbers for the dinosaurs to feed on. Even better, though, is that such details could lend a better understanding of how climate change could affect the present world.