More than 160 million years ago, long-necked dinosaurs called sauropods lumbered through the ancient lagoons that dotted what is now Great Britain. Now, dozens of their footprints have been found on the forbidding, wave-pounded coast of Scotland's Isle of Skye.

Standing on Skye's rocky shores, you might mistake the huge footprints for tidal pools—except that on second glance, you'd see that the pools trace the toes and fleshy heels of dinosaurs.

“These tracks were sort of hiding in plain sight for years,” says University of Southern California paleontologist Michael Habib, who wasn't involved with the discovery. “It goes to show how sauropods are so much larger than everything else, that we field paleontologists are rarely looking for something of that scale at first.”

Amid the large prints, the team also found distinctive three-toed footprints made by theropods, likely creatures that were older cousins of the Cretaceous-period Tyrannosaurus rex.

The full suite of footprints, unveiled in the Scottish Journal of Geology on April 2, provides a rare glimpse into the Middle Jurassic, a period spanning 164 to 174 million years ago that so far has yielded few dinosaur fossils of any kind. The latest discovery helps cement the Isle of Skye as a key region for bringing this little understood era to life.

“The Middle Jurassic was a pretty important time: It was some time around then that the first birds took to the sky, the first tyrannosaurs were evolving, [and] the first really colossal sauropods were getting their start,” says study co-author and National Geographic grantee Steve Brusatte, a paleontologist at the University of Edinburgh.

“Skye is one of the few places you can find these fossils.”

Water, Water Everywhere

In April 2016, researchers Davide Foffa and Hong-Yu Yi stumbled across the new footprints at a site called Rubha nam Brathairean, or Brother's Point. In 2017, Brusatte and his student Paige dePolo returned to map the site and interpret its tracks in fieldwork funded by the National Geographic Society.

To some, the word “fieldwork” may invoke an image of Indiana Jones standing in a desert. But on Skye, being in the field involved cold, rain-flecked winds constantly swirled overhead, tossing around the drones that the researchers had been hoping to use for mapping the region. High tides also regularly flooded the coastal trackways.

“I had a timepiece on my backpack, and we were always checking the time. 'Right about now is when the water is supposed to rise—oh, there it is,'” says dePolo, the study's lead author and a visiting researcher at the Nevada State Museum Las Vegas. “You get used to it.”

To scan the tracks during low tides, dePolo invented what she calls the intervalometer: two offset cameras mounted on an easily portable pole. Just as our two eyes let us see depth, the two cameras allowed dePolo and a colleague to map the trackways in 3-D as they walked.

Successful Sauropods

Like Skye's only other known set of sauropod footprints, the newfound prints were made in fine-grained lagoon sediments. Based on these similarities, dePolo and Brusatte say that sauropods in Skye—and perhaps elsewhere—regularly waded in coastal shallows.

In a way, the discovery brings scientists' understanding of sauropods full circle. In the early 1900s, paleontologists incorrectly viewed long-necked dinosaurs as lumbering brutes confined to swamps, their heavy bodies buoyed by water. Based on evidence gathered since then, it seems the behemoths did walk on terra firma, and they achieved global distribution. Sauropod bones and footprints have been found on all seven continents—including Antarctica.

“It wasn't that the water was the only place they could live and just had to languish,” says Brusatte. “Instead, we're now saying that they were so dynamic and so energetic—that they were so successful—that they were probably exploring whatever environments they could.”

Even more footprints will probably emerge from Skye. Brusatte's team has already identified additional candidate trackways, and dePolo will be leading their study when she returns to Edinburgh this fall to pursue her Ph.D.