Dinosaurs once dominated the world — but they spent their first 30 million years stranded on its geographic fringes. Large dinosaurs flourished near the poles, but only a few small ones, no larger than ostriches, managed to gain a foothold in the hotter low latitudes. nature 
Tracking ancient plant growth by analyzing carbon isotopes in nodules of petrified soil in the rock layers revealed repeated spikes and dips in the amount of ‘heavy’ carbon-13, a sign of major ecological disruption. These spikes lined up with sudden changes in fossil pollen trapped in the rocks, indicating periodic shifts between plant species adapted to wet conditions and those that preferred an arid environment.
This unstable environment could have prevented large dinosaurs from surviving. Big dinosaurs required a constant supply of food as they grew from hatchlings to as large as 4,000 kilograms over 10–20 years.
By comparison, the much smaller reptiles that inhabited what is now the southwestern United States rarely topped 1,500 kilograms. They grew more slowly and needed less food. In these hot, dry, fluctuating climates, things that are small have a better chance of surviving.
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I deleted all of the proper citation from these paragraphs to see how it might read.
See Traveling Python for an article with rampant code-centric citation, an equal distraction in story telling unless it is too the story.