It might be a place where we often get a glimpse of the future, but NASA’s Goddard Space Flight Center has just opened a window into the past.

In the parking lot of the major research laboratory, a local dinosaur track expert spotted a slab of rock jutting out of the ground to the side of the tarmac as he was dropping his wife off at work in 2012. After a quick look, he identified a 30-centimeter-wide (12-inch) dinosaur track. Following excavations, researchers have been studying a slab that contains some 70 prints, and have published their results in Scientific Reports.

Despite being only a few square meters in size, the trackway has preserved the footprints of an astonishing number of species, and even offers insights into their behavior. The team found the tracks from what they think are at least eight different species of dinosaur, mammal, and pterosaur, providing a wonderful snapshot of a few days some 100 million years ago.

At one point, an adult nodosaur – a large well-armored, heavily built herbivore – passed through what back then would have been the edge of a wetland. Astonishingly it seems that the nodosaur likely had a baby in tow, which seems to have slipped on the edge of the adult's footprint and slid into it. A long-necked sauropod sauntered past, as pterosaurs landed in the mud and started grubbing for food.

Four small crow-sized theropods padded across the mud flats, most likely on the hunt for creatures such as the small mammals that were scurrying through the swamp, pausing occasionally to sit on their haunches. And it is these imprints, made by our distant ancestors, that are the most exciting part of the trackway.  

So far, researchers have been able to identify a total of 26 mammalian tracks, making this one of the highest concentrations of mammal tracks ever discovered. Not only that, but with one print measuring 26 square centimeters (4 square inches), the trackway also contains the single largest mammal track found from the Cretaceous period. The animal that made it all that time ago was probably around the size of a modern-day raccoon.

“The concentration of mammal tracks on this site is orders of magnitude higher than any other site in the world,” said Martin Lockley, who co-authored the new paper. “I don't think I've ever seen a slab this size, which is a couple of square meters, where you have over 70 footprints of so many different types. This is the mother lode of Cretaceous mammal tracks.”

It is thought that back then, the carpark was likely the edge of a swamp or wetland that would eventually become the suburbs of Washington DC, and that during one day – or perhaps over two – the menagerie of prehistoric creatures all crossed this one spot, leaving their indelible marks behind.