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Palaeontology: Faecal forensics document the rise of dinosaurs (N&V) *IMAGES*
Fossilized samples of faeces and vomit have been used to reconstruct the rise of the dinosaurs to become the dominant players in Earth’s ancient ecosystems, as reported in a Nature paper this week.
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.
Martin Qvarnström, Grzegorz Niedźwiedzki and colleagues investigate this transition by reconstructing food webs using over 500 fossilized remains of digestive material (such as faeces or vomit), known as bromalites, from the Polish Basin, which span the Late Triassic to earliest Jurassic. 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 authors 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. Further research using this method could help to clarify this evolutionary history in other parts of the world.
