New research into fossilized feces, vomit, and stomach contents has revealed how dinosaurs gradually rose to dominate Earth, providing insights into a 30-million-year evolutionary transition. This study, published in Nature, analyzed more than 500 fossilized remains, known as bromalites, from the Polish Basin. These remains preserved direct evidence of ancient diets, ecosystems, and interactions, offering clues to how early dinosaurs adapted and thrived in a changing environment.
Dinosaurs first appeared at least 230 million years ago during the late Triassic period but did not become dominant until the start of the Jurassic, around 200 million years ago. The transition from small omnivorous species to the towering herbivores and fierce carnivores of the Jurassic has been a subject of scientific debate. The fossilized remains examined in this study contained traces of insects, plants, fish, and small animals, revealing a diverse diet among early dinosaurs and their ancestors.
One of the key findings involved an early dinosaur relative, Silesaurus, a small omnivorous creature weighing around 15 kilograms. In a world dominated by large, barrel-chested herbivores like dicynodonts, Silesaurus had a significant advantage: its adaptability. By consuming insects, fish, and plants, it could adjust to environmental changes better than its herbivorous competitors. This adaptability became crucial during periods of environmental upheaval, such as the Carnian Pluvial Episode, a time of increased rainfall that spurred the growth of new plant species. While larger herbivores struggled to adapt, Silesaurus and other early dinosaurs thrived, exploiting the new food sources.
The study revealed that the bromalites increased in size over time, reflecting the growth of the animals producing them. This growth marked a transition in ecosystems, with larger plant-eating dinosaurs emerging, followed by larger carnivores that preyed upon them. By the start of the Jurassic, dinosaurs had firmly established themselves as the dominant life forms, reshaping the landscape with their presence.
Two primary theories have long been proposed to explain the rise of dinosaurs. One suggests that dinosaurs had inherent evolutionary advantages, such as upright posture, that allowed them to outcompete other species. The other argues that environmental changes, such as volcanic activity or climate shifts, wiped out many competing species, creating opportunities for dinosaurs to thrive. This study supports a combination of both theories. Early dinosaurs used their adaptability and evolutionary traits to capitalize on environmental disruptions that weakened their rivals, gradually ascending to dominance.
Despite these findings, the study is not without limitations. The research focused exclusively on the Polish Basin, a northern region of the ancient supercontinent Pangea. Further studies in other regions, such as the southern parts of Pangea where dinosaurs first appeared, could provide additional context and expand the model developed by the researchers.
Fossilized bromalites offer a rare and invaluable glimpse into the ancient world, revealing details about diet, predator-prey relationships, and ecological changes. By linking the contents of these remains to their producers, scientists can reconstruct ancient food webs and understand how species interacted in their environments. This study highlights the power of trace fossils to unlock secrets of evolution and sheds light on the critical period when dinosaurs began their journey to becoming Earth’s dominant animals.