Fossilized Digestive Contents Shed Light on Rise of Dinosaurs

Paleontologists from Sweden and Poland have examined hundreds of fossilized samples of feces and vomit from the Polish Basin in central Europe to reconstruct the rise of the dinosaurs to become the dominant players in Earth’s ancient ecosystems.

Fossil records show that dinosaurs evolved during the middle part of the Triassic period (247 to 237 million years ago).

However, the domination of dinosaurs in terrestrial ecosystems was not seen until approximately 30 million years later, early in the Jurassic period.

Many non-dinosaur tetrapods (four-limbed vertebrates) were displaced during this time, but what caused dinosaurs to dominate the ecosystem has remained in question.

“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.”

Dr. Qvarnström and his colleagues investigated this transition by reconstructing food webs using over 500 fossilized remains of digestive material (such as feces or vomit), known as bromalites, from the Polish Basin, which span the Late Triassic to earliest Jurassic.

“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.”

“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.”

Analyses of these remains (including 3D imaging of their internal structures to reveal undigested food contents) were compared to the existing fossil record, along with climate and plant data, to estimate the changes in size and abundance of vertebrates during this period.

These data indicate that non-dinosaur tetrapods were displaced by the omnivorous ancestors of early dinosaurs, who evolved to become the first carnivorous and herbivorous dinosaurs towards the end of the Triassic era.

At this point, the researchers suggest that environmental changes linked to increased volcanic activity may have led to a more diverse range of plants to feed on, followed by the emergence of larger and more diverse herbivore species.

This, in turn, led to the evolution of larger carnivorous dinosaurs by the beginning of the Jurassic period, and completed the transition to dinosaur domination within the ecosystem.

This analysis sheds light on the emergence of dinosaur dominance within the ecosystem of the Polish Basin.

“Our results support the idea that stochastic processes coupled with a competitive advantage enabled the enormous evolutionary success of dinosaurs,” the authors said.

“The dinosaurs rose to supremacy in a stepwise fashion across 30 million years of evolution.”

“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 team’s paper was published in the journal Nature.

_____

M. Qvarnström et al. Digestive contents and food webs record the advent of dinosaur supremacy. Nature, published online November 27, 2024; doi: 10.1038/s41586-024-08265-4