Once upon a time, a tiny blackbird-sized dinosaur was caught in a Korean rainstorm. As the raindrops fell, the nimble Minisauripus stepped on firm, sticky mud, leaving a “perfect” impression for researchers to find tens of millions of years later.
Now, researchers say this small set of dinosaur tracks is the first of its kind to have “exquisitely preserved” skin traces for the entire footprint. What’s more, every single impression in the trackway is equally covered in dinosaur skin.
"These are the first tracks ever found where perfect skin impressions cover the entire surface of every track," said researcher Martin Lockley in a statement. Remnants of soft tissue, such as muscles and skin, are rare and often not well preserved. In fact, less than 1 percent of tracks show skin traces
Located near Jinju City, Korea, during large-scale excavations, five separate inch-long tracks were first spotted on a broken slab. In this case, when the dinosaur stepped on the surface of the ground, the skin texture of its foot was reproduced perfectly without any smears.
"The tracks were made on a very thin layer of fine mud," Lockley said, "rather like a coat of fresh paint only a millimeter thick."
Much like the fingerprints of humans, the skin patterns of different groups of dinosaurs varied and served as distinct markers for differences in anatomy. Furthermore, because the shallow and flat-bottomed print is consistently covered in dinosaur skin, it presents a perfect replica of what the foot looked like when the dinosaur was alive and offers insight into how the theropods might have walked.
Publishing their work in Scientific Reports, the authors describe the texture of the skin as resembling the grade of medium sandpaper. Each scale trace measures one-third or a half-millimeter in diameter and is similar to mummified skin found on the feat of feathered birds from China.
The discovery also expands the range of the Minisauripus, adding more to the limited literature on this rare small dinosaur. Dubbed the oldest report of Minisauripus from Korea, the find adds to a total of 95 tracks that are “pivotal to debates over whether small tracks represent small species, as the database suggests, or juveniles of large species.”