This is not something you see every day. Footprints measuring up to 1.25 meters in length, were found on the ceiling of a cave in a karstic cave in southern France, on the Causse Méjean plateau. It is suspected that they were left by a kind of Titanosaur. Artists reconstruction of a Titanosaur walking on the ceiling is to the right.
This prints date to the Bathonian age (ca. 168–166 Ma), which is near the middle of the Jurassic. Some of the tracks, found in three different trackways, are very detailed. And yes, it is possible (and not terribly uncommon) to erect a new species on the basis of footprints. In this case, the new species is Occitanopodus gandi, igen. et isp. nov.
The environment at the time is reconstructed to have been a lake, near the shore. I’ve only read the summaries, so I’m not sure of the exact context and orientation, but limestones from the middle Jurassic in Southern France are sometimes very tilted, so I suppose this could be an upside down (or at least, tilted over 90 degrees) layer. The find is some 500 meters below the surface, which counts as deep in a cave.
Moreau, Jean-David et al. 2020.
Middle Jurassic tracks of sauropod dinosaurs in a deep karst cave in France. Journal of Vertebrate Paleontology. Article: e1728286 | Received 29 Oct 2018, Accepted 13 Dec 2019, Published online: 25 Mar 2020.