Climate change was essential for dinosaurs to spread across the planet, says study

Climate change was essential for a group of dinosaurs called sauropodomorphs spread across the planet about 230 to 180 million years ago.

The data are from a study with the participation of researchers from the University of São Paulo (USP), published in the scientific journal Current Biology.

Based on data obtained from fossils and meteorological simulations that allow estimating the climatic conditions of our planet in the past, experts estimate that 230 million years ago, tropical regions had large variations in temperature and rainfall. This factor limited the presence of sauropodomorphs to places with a milder climate, far from the tropics.

However, the scenario changes with the increase in humidity, related to the emergence of new oceans from the fragmentation of the supercontinent Pangea, around 200 million years ago. The changes allowed the group to reach areas with a tropical climate.

Paleontologist Pedro Godoy, one of the authors of the work, explains that the period covered by the research extended from the Upper Triassic to the end of the Lower Jurassic, between 230 and 180 million years before present times.

“It was selected because it encompasses the first million years of dinosaur evolution, the extinction event that took place in the transition from the Triassic to the Jurassic, 200 million years ago, and the period of expansion of the geographic distribution of some groups, during the Jurassic. Inferior”, says Godoy, a postdoctoral fellow at the Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, in a statement.

“During this period, what we see in the layout of the continents is that the supercontinent Pangea was divided into two main blocks: Laurasia to the North, which included North America, Europe and Asia, and Gondwana to the South, which included South America, Africa, Antarctica, Australia, India and Madagascar”, he continues.

For the estimates, scholars used climate data such as average annual temperature and precipitation, in addition to seasonal temperature variation. “They come from models that combine environmental information from the fossil record and meteorological simulations to generate highly accurate data. Thus, we have ‘paleoclimatic’ data for each of the locations where dinosaur fossils were found”, explains Godoy.

The paleontologist adds that the Triassic period was a hotter and drier period, while the Jurassic is characterized by an increase in humidity, related to the fragmentation of the supercontinent Pangea, which gave rise to new oceans. “Some studies also suggest that the Triassic had more drastic seasonal variations, even in tropical regions,” he says.

tropical journey

The main change in the distribution of dinosaurs in the period occurred in relation to the sauropodomorphs. The group includes herbivores and long-necked animals, such as Apatosaurus. However, during the Upper Triassic, the first representatives of the group were much smaller, still without such long necks, says the paleontologist.

“In terms of geographic distribution, during the Upper Triassic they were more restricted to temperate regions, that is, more distant from the tropics. In fact, one of the most important regions for us to understand the origin of dinosaurs is Rio Grande do Sul, in Brazil, where some of the oldest specimens in the world were found.”

In the Lower Jurassic, the researchers observed that the sauropodomorphs were more spread across the globe, also inhabiting tropical regions. According to Godoy, this pattern is different from that observed for other dinosaurs and also for other tetrapods, which already inhabited tropical regions before the end of the Triassic.

“What our results show is that this change in geographic distribution was possibly due to changes in climate that occurred in the transition from the Triassic to the Jurassic”, he points out. “As explained, tropical regions during the Late Triassic had more extreme seasonal variations, which possibly limited the occurrence of the group in these regions. With increased humidity during the Jurassic, they were finally able to occupy these regions closer to the equator.”

Godoy states that the study opens the way for new research on how climate changes may have influenced the decline of other species.

“Easy access to this data also allows us to investigate the effects on other groups of animals and plants, which strengthens our knowledge on the subject and helps us build better predictions about possible future extinctions, such as those resulting from the current process of changes climate,” he concludes.

(With information from the Journal of USP)