Paleontologists spent decades dragging the largest dinosaurs of all time out of the water. From the 1970s on, during the fevered height of the Dinosaur Renaissance, experts pointed to anatomy and trackways to show that Brontosaurus and its kind were not swampbound layabouts as they had been portrayed for much of the 20th century. These were terrestrial animals who browsed along the fringes of conifer forests, the extensive system of airsacs running their their bodies actually making them unstable in water. A new generation of experts flipped conventional wisdom on its head. The idea that Diplodocus and other sauropods were habitual waders was overturned, putting the dinosaurian giants on solid ground.
Of course, dinosaurs have a habit of surprising us. Jurassic tracks from Scotland suggest that some sauropods regularly got their feet wet to wade through the ancient shallows.
The ancient footprints, Middle Jurassic in age and dating to about 170 million years ago, look like petrified potholes. That’s how they escaped attention until 2016, as they looked like nothing more than divots along the shore of the Isle of Skye. Impressions left by dinosaurian toes indicate that these aren’t just any impressions, though, and paleontologist Paige dePolo and colleagues argue that the prints were made by sauropod dinosaurs who tromped through Jurassic lagoons.
Dinosaurs often left tracks along ancient bodies of water. Lakes and streams were excellent places for footprints to accumulate, the moisture allowing the sediment to hold footprints and regular sedimentation covering the impressions. In this case, dePolo and coauthors point out, the track-bearing layers of limestone are fine-grained, contain the shell fragments from contemporary invertebrates, and show signs of burrowing by small marine organisms. The upshot is that the dinosaur tracks indicate that the dinosaurs were walking through shallow water along the accessible portions of an ancient lagoon.
This doesn’t mean that the sauropods were happily swimming along. The roughly 50 tracks represent four-on-the-floor locomotion. We’re not going back to images of Brachiosaurus neck-deep in Jurassic lakes. But these dinosaurs clearly weren’t aquaphobic. They ambled along through the salty water as they went about their Jurassic business. It’s an image between the traditional and Dinosaur Renaissance views, further reminding us that living creatures will always defy our expectations.