Fossil footprints unearth bustling ancient dinosaur ecosystem

Scientists have discovered fossil footprints of a thriving community of dinosaurs along the shores of Scotland's Isle of Skye, unearthing clues about the strolls taken by the giant reptiles, and the region's ecosystem between 174 and 164 million years ago.

According to the study, published in the journal PLOS One, the Isle of Skye was home to dinosaurs, including the plate-backed stegosaurus, that stomped across the ancient coastline during the Middle Jurassic Period. The researchers, including Paige dePolo from the University of Edinburgh in Scotland, said this period was a time of major evolutionary diversification in many dinosaur groups.

However, they said dinosaur fossils from this time period are generally rare, with the exception of the Isle of Skye. This region, the scientists said, yielded body and trace fossils of diverse Middle Jurassic ecosystems, serving as a valuable location for paleontological science as well as tourism. In the study, dePolo and her colleagues described two recently discovered fossil sites preserving around 50 dinosaur footprints on ancient coastal wetlands.

The scientists reported the first record on the Isle of Skye of a track type called Deltapodus, which they said was most likely created by a stegosaurian (plate-backed) dinosaur. According to the researchers, these are the oldest Deltapodus tracks known, and the first strong evidence that stegosaurian dinosaurs were part of the island's Middle Jurassic fauna.

They also found three-toed footprints, representing multiple sizes of early carnivorous theropods, which are dinosaurs characterised by hollow bones and three-toed limbs. The study reported a series of other large tracks as well, tentatively identified as some of the oldest evidence of large-bodied herbivorous bird-hipped, ornithopod dinosaurs.

Considering all the pre-historic footprints, the scientists said these two sites expand the known diversity of what may have been a thriving ecosystem of Middle Jurassic dinosaurs in Scotland -- including at least one type of dinosaur (stegosaurs) not previously known from the region.

The findings, according to the researchers, reflect the importance of footprints as a source of information supplemental to body fossils. By revisiting previously explored regions, they believe, new sites can be found in areas that have long been popular for fossil prospecting.

The scientists noted that in this particular case, the trackways were only recently revealed by storm activity. "These new tracksites help us get a better sense of the variety of dinosaurs that lived near the coast of Skye during the Middle Jurassic than what we can glean from the island's body fossil record," dePolo said. "In particular, Deltapodus tracks give good evidence that stegosaurs lived on Skye at this time," she added.

The new tracksites, the researchers said, provide a much clearer picture of the dinosaurs that lived in Scotland 170 million years ago. "We knew there were giant long-necked sauropods and jeep-sized carnivores, but we can now add plate-backed stegosaurs to that roster, and maybe even primitive cousins of the duck-billed dinosaurs too," said study co-author Stephen Brusatte from the University of Edinburgh.