Fossilized samples of feces and vomit were used to reconstruct the rise of the dinosaurs, who became the dominant players in Earth’s ancient ecosystems, according to an article published in Nature.
Fossil records show that dinosaurs evolved during the middle part of the Triassic period (247 to 237 million years ago). However, the dominance of dinosaurs in terrestrial ecosystems only occurred about 30 million years later, in the early Jurassic period.
Many tetrapods (vertebrates with four limbs) that were not dinosaurs were displaced during this period, but what led the dinosaurs to dominate the ecosystem remains a mystery.
Martin Qvarnström, Grzegorz Niedźwiedzki, and colleagues investigate this transition by reconstructing food webs using more than 500 fossilized remains of digestive material (such as feces or vomit), known as bromalites, from the Polish Basin, spanning from the Late Triassic to the Early Jurassic.
The analyses of these remains (including 3D images of their internal structures to reveal undigested food contents) were compared with the existing fossil record, together with climatic and plant data, to estimate changes in the size and abundance of vertebrates during this period.
These data indicate that non-dinosaur tetrapods were displaced by the omnivorous ancestors of the earliest dinosaurs, which evolved to become the first carnivorous and herbivorous dinosaurs by the end of the Triassic.
At this point, the authors suggest that environmental changes linked to increased volcanic activity may have led to a greater diversity of plants for feeding, followed by the appearance of larger and more diverse herbivorous species. This, in turn, led to the evolution of larger carnivorous dinosaurs in the early Jurassic and completed the transition to dinosaur dominance in the ecosystem.
This analysis sheds light on the emergence of dinosaur dominance in the ecosystem of the Polish Basin. Other investigations using this method could help clarify this evolutionary history in other parts of the world.
