Crews of workers exploding rock off a highway outside Grahamstown, near the southern coast of South Africa, discovered something historic recently: a trove of fossils, many of which are hundreds of millions of years old, according to News24.

The fossils represent a wide variety of undocumented species, from plants to invertebrates. The majority date to nearly 360 million years ago, when the Earth was made up of supercontinents, and Pangaea had yet to form. 

Most of the fossils are from marine life, which isn’t all that surprising: before animals roamed the land on Earth they swam its oceans. Among the findings was a undocumented species of clam, for example, as well as a very well-preserved fertile material from a tree, according to News24. 

This isn’t the first time road maintenance has led to new fossil discoveries; South African crews have stumbled upon fossils at least four times, one paleontologist told News24. 

After workers are through excavating the fossils from the latest find, they will continue work on what they set out to build: a highway rest stop. There they plan to also post a sign reminding visitors that fossils were once found at this site, and the land they stand on is ancient.