Heads up! Scientists have discovered the prehistoric footprints of a colossal dinosaur on the roof of a cave in France. Nope, this doesn't mean that giant dinosaurs were dancing on the ceilings of caves like a sticky-footed Spiderman, although it goes to show the wealth of prehistoric discoveries that could be found lurking in the geology all around us.

Recently reported in the Journal of Vertebrate Paleontology, researchers from the University of Burgundy–Franche-Comté discovered the three dinosaur trackways during an expedition in 2015 around the labyrinth-like Castelbouc Cave beneath the Causse Méjean plateau in southern France.

The tracks, made some 166 million to 168 million years ago, are extremely well-preserved, complete with impressions of digits, pads, and even claws. At a stonking 1.25 meters (4 feet) long, the prints belonged to some of the largest known dinosaurs worldwide.

It’s not certain what species of sauropod was responsible for the tracks, not least because they date to an age in the Middle Jurassic when sauropod evolution is hazy. However, their size suggests they might have belonged to a titanosaur, a diverse group of long-necked sauropods that includes the largest land animals known to have ever existed, such as the 37-meter-long (121-foot) Patagotitan that roamed southern Argentina. 

So, how did these gentle giants' footprints end up on the cave roof? Back when sauropods was treading the Earth, the site was on the planet’s surface, but geological processes have since buried the sediments over the course of millions of years. With a bit of luck, the processes create a scenario where it appears the impression of the feet is embossed on the ceiling. 

Reaching this portion of the cave nowadays is not so easy. The tracks are found some 500 meters (1,640 feet) beneath Earth’s surface, only accessible after traversing a winding network of caverns that are often flooded with water after rainy spells. As the researchers note, finding dinosaur tracks in this kind of environment is extremely rare, but it suggests that the scarcely explored caves of the world could be home to much more paleolithic treasures than thought.  

“This discovery demonstrates the great potential of prospecting in deep karst caves that can occasionally offer larger and better-preserved surfaces than outdoor outcrops,” the study authors write. 

It’s not the first time dinosaur footprints in unusual circumstances have been discovered though. Back in February, researchers published another paper documenting a set of smaller dinosaur tracks imprinted on the roof of a cave near Mount Morgan in Queensland, Australia, and curious footprints found in a Texas quarry seem to suggest these giant dinosaurs traveled in water by punting themselves along the bottom.