Fossilised droppings tell the story of dinosaurs’ rise to power

200-million-year-old feces and vomit contents are helping to reveal how dinosaurs took over the world at the start of the Jurassic Period.

Well-preserved plants, bones, fish fragments and even whole insects embedded in the very different shapes and sizes of ancient animal droppings show that the dinosaurs survived their extensive diets in a changing ecosystem compared to other animal groups. This then led them to grow and eventually establish a “dynasty on the ground,” he says Martin Qvarnström at the University of Uppsala, Sweden.

Fossil evidence shows that the first dinosaurs – marked by hip joints that place the legs under the body like mammals, instead of extending out to the sides like lizards – appeared. more than 230 million years ago During the Triassic period. For tens of millions of years, these early dinosaurs blended into a landscape filled with many other types of reptiles. About 200 million years ago, however, the dinosaurs essentially took over the planet, while most other reptiles disappeared. Extinction at the end of the Triassic at that time

What led to this domination has remained somewhat of a mystery. Qvarnström and his colleagues suspected that significant clues could be found hidden in bromalites – fossilized feces and vomit – among dinosaurs and other animals. So they collected 532 saved examples Polish Geological Institutewhich were collected by the first research teams between 1996 and 2017 in eight sites in Poland.

The team estimated the age of each bromalite from the layers of sediment they found and then used its size – ranging from a few millimeters to “fairly large masses of faeces” – and shape to match the animal that likely produced it. The researchers then 3D scanned the fossils to explore their contents. “We realized they are full of leftovers,” says Qvarnström.

Combined with the known fossil record and past climate information, the researchers determined that the rise of the dinosaurs occurred in several steps. First, the ancestors of the early dinosaurs began to be more omnivorous than the non-dinosaurs. Then they became the first meat-eating and plant-eating dinosaurs.

At that time, the increase in volcanic eruptions and the displacement of tectonic plates led to the development of floods and waterways. As a result, moisture and climate change appear to have resulted in a greater variety of plants, leading to larger and more diverse herbivorous dinosaurs. Meanwhile, the non-dinosaurs – like the one-ton plant-eating dicynodont. Lisowic, whose droppings contained mainly the remains of conifers – which were unable to adapt to the ever-changing vegetation.

As the herbivorous dinosaurs grew, so did their predators. When large carnivorous dinosaurs began to appear at the beginning of the Jurassic Period – about 30 million years after the first dinosaurs appeared – the transition to a dinosaur-dominated world was complete, says Qvarnström.

“Research shows how climate primarily affected dominant plants, which in turn provided opportunities for new herbivores at certain points,” he says. Michael Benton at the University of Bristol, UK, who was not involved in the study.

While it is difficult to be sure that the researchers have matched the droppings to the right animals, the findings nevertheless support earlier work in South America, which suggests that dinosaur species were expanding significantly before the great climate change. “But it took the late Triassic mass extinction to set the last steps of the takeover in motion.”

In fact Emma Dunne At Germany’s Friedrich-Alexander University, research helps answer long-standing questions about the rise of the dinosaurs. “It’s not every day you see fossil poo in such an influential journal,” says Dunn, who was not involved in the research. “Of course it’s fun, but it’s also very useful for understanding prehistoric environments. So if you think of the early evolution of dinosaurs as some kind of puzzle with missing pieces, just throw a lot of new pieces in there.