Dinosaurs did not take over terrestrial ecosystems in one sudden event. In the Polish Basin, the change from Late Triassic communities to dinosaur-dominated Early Jurassic faunas unfolded through a sequence of ecological shifts. Fossilised digestive remains, bite traces, bones and plant records let researchers study what animals ate and when different feeding roles appeared.
What digestive fossils can reveal
Coprolites, cololites and regurgitated remains are grouped as bromalites. They can preserve pieces of plants, insects, fish or bones that an animal swallowed. Their contents provide direct evidence of ingestion, but identifying the producer can be difficult. A coprolite is not automatically attributable to the most familiar animal from the same quarry.
A 2024 study analysed more than 500 bromalites and other feeding fossils from five vertebrate assemblages in the Polish Basin. Synchrotron imaging and careful fossil comparisons helped researchers reconstruct changing food webs across about 30 million years. The record is unusually valuable because it combines traces of feeding with fossils of the animals and plants in the same regional succession.
A gradual reorganisation of food webs
Early in the sequence, dinosaur precursors were a minor part of communities dominated by other reptile groups. Small opportunistic animals with varied diets appeared before large dinosaur herbivores and predators became common. Later assemblages contain evidence for insect- and fish-eating theropods, small omnivores, large sauropodomorph herbivores and early ornithischians.
Climate and vegetation changed during the same interval. As plant communities shifted, animals with different feeding adaptations gained or lost access to food. The authors suggest that dietary flexibility helped some dinosaur groups exploit new resources. Their study does not show a single contest in which dinosaurs simply defeated every rival. Climate, extinction, dispersal, anatomy and chance all contributed to the regional pattern.
Did dinosaurs become ecosystem engineers?
Large herbivores consume vegetation, break branches and move nutrients. In principle, those activities can alter plant structure and the resources available to smaller animals. Modern large herbivores provide models for the kinds of effects that may be possible, but they cannot prove exactly how a dinosaur changed a particular Mesozoic landscape.
For deep time, the strongest claims connect a proposed effect to evidence: feeding damage on leaves, plant material in gut contents, changing vegetation in sediment records, or repeated shifts in associated animal communities. A trampled path or a seed dispersed in dung is not demonstrated merely because a dinosaur was large. Direct evidence is uneven, and the scale of an effect is difficult to measure from fossils.
Regional history, not a universal template
The Polish sequence documents a clear local progression, but the authors caution that the rise of dinosaurs may have been uneven across Pangaea. Different basins preserve different rocks, climates and animals. The fossil record also favours some body sizes and burial settings over others.
This makes the case study useful without making it a rule for every continent. It shows how feeding fossils can turn a vague story about dominance into testable questions about diet and ecological roles. For a broader comparison of predator-prey links, see our overview of dinosaur food webs.
Frequently asked questions
Did dinosaurs dominate ecosystems as soon as they evolved?
No. In the Polish Basin record, dinosaurs and close precursors increased their ecological roles in stages over tens of millions of years.
What can a dinosaur coprolite prove?
Contents can show that food was swallowed. They usually do not identify the producer with certainty or reveal the animal's full diet across its life.
Did dinosaurs reshape vegetation by trampling and spreading seeds?
Those effects are plausible for large animals, but each claim needs direct evidence. Fossil size alone does not prove a specific ecosystem change.
Does the Polish Basin study explain dinosaur dominance everywhere?
It gives a detailed regional record. The authors propose that some patterns may be broader, but the timing differed between regions and needs comparison with other basins.