Knowledge Fossilized droppings describe the rise of the dinosaurs

Experts have reconstructed the early development of dinosaurs using fossilized faeces, vomit and intestinal contents. More than 500 such fossils have been examined, paleontologists write in the journal "Science".

Undigested food remains, plants and parts of prey animals were identified in the fossilized faeces. The analysis was real detective work, said Martin Qvarnström from Uppsala University in Sweden. "The ability to study what the animals ate and how they interacted with their environment helps us to understand what enabled the dinosaurs to succeed."

Beetles and charcoal in the remains

In addition to the digestive remains, the researchers used bone finds, footprints, bite marks, plant fossils and climate data to gain insights into the animal communities of the time. Lead author Grzegorz Niedzwiedzki explains: "The research material was collected over 25 years; it took us many years to piece it together into a coherent picture."

The research team used state-of-the-art imaging techniques to visualize the inner parts hidden in the fossils. They discovered the remains of fish, beetles, larger animals and plants. Based on the dietary preferences of early dinosaurs, they tried to find out more about life at that time.

They also discovered some surprising things. For example, the excrement of the first large herbivorous dinosaurs, the long-necked sauropods, not only contained large quantities of tree ferns, but also charcoal. The researchers suspect that the charcoal was ingested to detoxify the stomach contents, as ferns can be poisonous to herbivores.

Initially still in the minority

In the end, they divided the development of the dinosaurs into five phases. In the first phase, 231 to 228 million years ago, the immediate ancestors of dinosaurs such as the silesaurids lived. They tended to be small to medium-sized, herbivores or omnivores and were greatly outnumbered by other reptiles.

In the second phase, 220 to 210 million years ago, the first small carnivorous dinosaurs appeared, according to the study, which belong to the theropods and thus to the predecessors of birds. In the third phase, from 210 to 205 million years ago, the first large theropods and herbivorous or omnivorous bird dinosaurs appeared.

Up to this point, dinosaurs and their ancestors were not yet so dominant. But by the fourth phase, 204 to 202 million years ago, they began to make up the majority of animals, according to the study. Small four-legged lizard pelvic dinosaurs appeared, from which the largest land animals on earth would later emerge.

According to the researchers, the fifth phase began 201 million years ago, i.e. at the Jurassic boundary: at that time, various dinosaurs of all sizes and species dominated the ecosystems.

Changes in the environment as a trigger

The phases relate to present-day Poland, where most of the finds studied come from, but the scientists suspect similar sequences in other parts of the world. They attribute the changes in the animal world to upheavals in the environment, such as climate change.

At the end of the Triassic, one of the five great mass extinctions in the history of the earth occurred, presumably due to intense volcanic activity. The carbon dioxide content of the air and the acidification of the oceans rose sharply as a result. The researchers suspect that the dinosaurs were better able to cope with the new environmental conditions than their food competitors and that they were able to make better use of the new food supply due to changes in the plant world.

SDA