For decades, scientists have worked to understand the demise of the dinosaurs. But what about the circumstances that ushered in the dinosaurs?

Decidedly less is known about how the dinosaurs first arrived, or how they quickly came to dominate the planet. New research, however, suggests they benefited from another mass extinction, some 232 million years ago.

The earliest dinosaur species show up in the fossil record around 245 million years ago, at the beginning of the Triassic Period. Dinosaurs were relatively rare, however, until roughly 13 million years later.

A survey of ancient rock deposits in Northern Italy's Dolomites revealed the suddenness with which dinosaurs overwhelmed the landscape. There are almost no dinosaur footprints in the Triassic Period, but after the seismic events during the Carnian, the earliest age of the Late Triassic epoch, dinosaur footprints become ubiquitous.

Surveys of the fossil records recovered from rocks in Argentina and Brazil revealed a similarly timed explosion of dinosaur skeletons.

"We were excited to see that the footprints and skeletons told the same story," Massimo Bernardi, a researcher at the University of Bristol, said in a news release. "We had been studying the footprints in the Dolomites for some time, and it's amazing how clear cut the change from 'no dinosaurs' to 'all dinosaurs' was."

The rise of the dinosaurs corresponds with the tail end of the Carnian Pluvial Episode, a series of cataclysmic climate shifts that inspired dramatic biotic turnover on land and in the seas. Previous studies suggest a series of explosive volcanic eruptions in western Canada precipitated periods of global warming and acid rain.

During the latest study, scientists found evidence of dramatic climatic shifts in the rock sequences collected from the Dolomites.

"There were four pulses of warming and climate perturbation, all within a million years or so," said Piero Gianolla, from the University of Ferrara. "This must have led to repeated extinctions."

Researchers published their findings in the journal Nature Communications.

"The discovery of the existence of a link between the first diversification of dinosaurs and a global mass extinction is important," said Bristol professor Mike Benton. "The extinction didn't just clear the way for the age of the dinosaurs, but also for the origins of many modern groups, including lizards, crocodiles, turtles, and mammals -- key land animals today."

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