In an international collaboration, researchers at Uppsala University have been able to identify undigested food remains, plants and prey in the fossilised faeces of dinosaurs. These analyses of hundreds of samples provide clues about the role dinosaurs played in the ecosystem around 200 million years ago. The findings have been published in the journal Nature.
"Piecing together 'who ate whom' in the past is true detective work," says Martin Qvarnström, researcher at the Department of Organismal Biology and lead author of the study. "Being able to examine what animals ate and how they interacted with their environment helps us understand what enabled dinosaurs to be so successful."
Palaeontologists from Uppsala University, in collaboration with researchers from Norway, Poland and Hungary, have examined hundreds of samples using advanced synchrotron imaging to visualise the hidden, internal parts of the fossilised faeces, known as coprolites, in detail. By identifying undigested food remains, plants and prey, they have recreated the structure of the ecosystems at the time when dinosaurs began their success story.
The study focused on a previously underexplored region, Polish Basin, located in the Late Triassic time in the in the northern parts of the then supercontinent Pangea. The researchers built up a comprehensive picture of the Triassic and Jurassic ecosystems (from about 230 to 200 million years ago) by combining the information from the coprolites with climate data and information from other fossils: plants, bite marks, vomit, footprints and bones.
"The research material was collected over a period of 25 years. It took us many years to piece everything together into a coherent picture," says Grzegorz Niedźwiedzki, researcher at the Department of Organismal Biology and the study's senior author. "Our research is innovative because we have chosen to understand the biology of early dinosaurs based on their dietary preferences. There were many surprising discoveries along the way."
The coprolites contained remains of fish, insects, larger animals and plants, some of which were unusually well preserved, including small beetles and semi-complete fish. Other coprolites contained bones chewed up by predators that, like today's hyenas, crushed bones to obtain salts and marrow. The contents of coprolites from the first large herbivorous dinosaurs, the long-necked sauropods, surprised the researchers. These contained large quantities of tree ferns, but also other types of plants, and charcoal. The palaeontologists hypothesise that charcoal was ingested to detoxify stomach contents, as ferns can be toxic to herbivores.
The research addresses a significant gap in current knowledge: the first 30 million years of dinosaur evolution during the Late Triassic period. Although much is known about their lives and extinction, the ecological and evolutionary processes that led to their rise are largely unexplored. The study results in a five-step model of dinosaur evolution that the researchers believe can explain global patterns.
The team emphasises that understanding how the first dinosaurs achieved their success can offer valuable insights into prehistoric ecosystems and evolutionary processes in general. The results show that dietary diversity and adaptability were crucial survival traits during the environmental changes of the Late Triassic.
"Unfortunately, climate change and mass extinctions are not just a thing of the past. By studying past ecosystems, we gain a better understanding of how life adapts and thrives under changing environmental conditions," says Qvarnström.
"The way to avoid extinction is to eat a lot of plants, which is exactly what the early herbivorous dinosaurs did. The reason for their evolutionary success is a true love of green and fresh plant shoots," Niedzwiedzki concludes.
