A collection of fossilized footprints preserved on an ancient shoreline in northwestern Italy is providing new evidence that dinosaurs may have risen to ecological dominance far earlier than scientists once believed.
The findings, published in the journal Gondwana Research, are based on a reanalysis of trackways discovered near the coastal town of Lerici. Researchers concluded that dinosaurs had already become the most successful large terrestrial animals in the region more than 230 million years ago during the earliest stages of the Late Triassic period.
The study was led by Lorenzo Marchetti of the Museum für Naturkunde Berlin and suggests that Lerici may represent the oldest known site where dinosaurs clearly dominated an ecosystem.
Unlike many dinosaur discoveries that rely on fossilized bones or teeth, the research focused entirely on fossil footprints preserved in a rock surface measuring only about six square meters.
Although relatively small, the site contains an unusually rich collection of tracks that allowed scientists to reconstruct the diversity of animals living in the area during a critical period of evolutionary history.
Paleontologists who study fossil tracks use a classification system known as ichnospecies, which groups footprints based on shared characteristics rather than direct links to skeletal fossils.
While identifying the exact species responsible for a footprint is often impossible, the shape and structure of tracks frequently provide enough information to determine the broader group of animals that created them.
At Lerici, researchers identified five distinct ichnospecies.
Two of the track types were attributed to non-dinosaur reptiles. One appears to have been made by a pseudosuchian, a distant ancestor of modern crocodiles and alligators. Another likely belonged to a lepidosauromorph, a reptile lineage more closely related to modern lizards than to dinosaurs.
The remaining three ichnospecies were identified as dinosaur tracks.
One set of footprints was attributed to a theropod, the group that would eventually produce predators such as Tyrannosaurus rex. The other two track types were linked to early sauropodomorphs, ancestors of the giant long-necked dinosaurs that later became iconic during the Jurassic Period.
The distribution of the tracks suggests that dinosaurs not only outnumbered their reptilian competitors at the site but also displayed greater ecological diversity.
Researchers argue that this level of diversity indicates dinosaurs were already expanding rapidly and establishing themselves as dominant members of terrestrial ecosystems.
To explain how dinosaurs achieved such success so quickly, the research team pointed to a major climatic event known as the Carnian Pluvial Episode, or CPE.
According to the study, massive volcanic eruptions approximately 234 million years ago dramatically altered Earth’s climate. Increased atmospheric temperatures boosted ocean evaporation, leading to exceptionally high levels of rainfall across Pangaea, the supercontinent that existed at the time.
Scientists believe these wetter conditions persisted for roughly one to two million years and fundamentally reshaped ecosystems worldwide.
Before the Carnian Pluvial Episode, dinosaur lineages appear to have been largely restricted to southern regions of Pangaea. Vast desert systems created natural barriers that limited their expansion into northern territories.
Meanwhile, other reptile groups occupied many ecological niches without significant competition from dinosaurs.
The climatic shift associated with the Carnian Pluvial Episode transformed many of those deserts into wetter and more hospitable environments.
Researchers argue that dinosaurs, particularly early sauropodomorphs, took advantage of these new conditions by rapidly expanding both their geographic range and species diversity.
The Lerici footprints appear to have been created during this transitional period when dinosaurs were beginning to spread into new habitats and establish ecological dominance.
One of the study’s most significant challenges involved demonstrating that the tracks truly belonged to dinosaurs rather than other reptiles living at the same time.
The answer, researchers say, lies in the anatomy reflected in the footprints themselves.
Early dinosaurs possessed relatively rigid ankle structures that limited rotational movement in their feet. Because of this, they no longer relied on a curved fifth toe, a feature commonly found in pseudosuchians.
Over evolutionary time, that fifth digit became reduced and eventually disappeared in dinosaurs.
The absence of this anatomical feature in the Lerici tracks provided one of the strongest pieces of evidence supporting the conclusion that the footprints were made by dinosaurs rather than their reptilian relatives.
Beyond its implications for dinosaur evolution, the study also proposes revisions to how certain sauropodomorph ichnospecies are classified.
Researchers say those changes could help improve the interpretation of fossil track sites around the world and provide a clearer picture of how dinosaur communities evolved during the Triassic Period.
The findings add a new dimension to scientists’ understanding of the rise of dinosaurs, suggesting that their ascent to ecological dominance may have begun earlier and progressed more rapidly than previously recognized.
For decades, paleontologists have debated exactly when dinosaurs transitioned from relatively minor members of Triassic ecosystems into the dominant terrestrial vertebrates that would rule the planet for more than 160 million years.
The fossil footprints at Lerici offer a rare snapshot of that transformation in progress.
Rather than depicting a world where dinosaurs were merely one group among many competing reptiles, the tracks suggest they had already become the leading large animals in at least some ecosystems shortly after major climatic changes reshaped the ancient world.
If confirmed by future discoveries, the Lerici site may stand as the earliest known evidence of dinosaurs establishing the ecological supremacy that would define much of the Mesozoic Era.
