Scientists analyze more than 500 fossilized gut remains from Late Triassic and Early Jurassic, revealing early dinosaurs’ diets, adaptability and how environmental shifts helped them dominate Earth’s ecosystems for over 30 million years
Dinosaurs first appeared in the fossil record during the Middle Triassic period, approximately 247 to 237 million years ago. However, it wasn’t until around 30 million years later, in the Early Jurassic, that they began to dominate terrestrial ecosystems.
During this time, many non-dinosaur tetrapods—four-limbed vertebrates—were gradually displaced. Yet, the reasons behind this dramatic shift in dominance have long puzzled scientists.
“Piecing together ‘who ate whom’ in the past is true detective work,” said Uppsala University paleontologist Martin Qvarnström. “Being able to examine what animals ate and how they interacted with their environment helps us understand what enabled dinosaurs to be so successful.”
To investigate this evolutionary transition, Dr. Qvarnström and his team reconstructed ancient food webs by analyzing over 500 fossilized digestive remains, known as bromalites, from the Polish Basin. These remains, which include fossilized feces and vomit, span the Late Triassic to the earliest Jurassic period and provide a unique window into the diets and ecological roles of early dinosaurs.
“The research material was collected over a period of 25 years,” said Dr. Grzegorz Niedźwiedzki, a paleontologist at Uppsala University and the Polish Geological Institute. “It took us many years to piece everything together into a coherent picture.”
(Photo: Martin Qvarnström)
“Our research is innovative because we have chosen to understand the biology of early dinosaurs based on their dietary preferences,” he added. “There were many surprising discoveries along the way.”
Using advanced techniques, including 3D imaging to examine the internal structures of the bromalites, the researchers identified undigested food remains and compared them to existing fossil records. They also incorporated data on climate and plant life to estimate changes in the size and abundance of vertebrates during this critical period. Their findings suggest that the omnivorous ancestors of early dinosaurs gradually displaced non-dinosaur tetrapods, evolving into the first carnivorous and herbivorous dinosaurs by the end of the Triassic.
The researchers propose that environmental changes, such as increased volcanic activity, played a significant role in this transition. These changes likely led to a greater diversity of plant life, which provided new food sources for herbivorous dinosaurs. Over time, this dietary expansion supported the evolution of larger and more diverse herbivores, which in turn paved the way for the emergence of larger carnivorous dinosaurs by the start of the Jurassic period. This step-by-step process ultimately established dinosaurs as the dominant species in terrestrial ecosystems.
“Our results support the idea that stochastic processes coupled with a competitive advantage enabled the enormous evolutionary success of dinosaurs,” the authors wrote. “The dinosaurs rose to supremacy in a stepwise fashion across 30 million years of evolution.”
The study highlights how the ecosystems of the Polish Basin provide a detailed snapshot of this evolutionary shift. The researchers believe that the processes observed in this region may reflect global patterns, offering new insights into how environmental factors shaped the rise of dinosaurs and their eventual gigantism.
“We suggest that the processes shown by the Polish data may explain global patterns, shedding new light on the environmentally governed emergence of dinosaur dominance and gigantism that endured until the end-Cretaceous mass extinction,” the authors concluded.
As reported by Ynetnews