When UChicago paleontologist Paul Sereno set out for the central Sahara in 2019, following clues from a decades-old report—a fossilized tooth and a dot on a map—he did not expect the expedition to culminate in the discovery of a new dinosaur species.

But for Sereno, the discovery was just the latest in a long career uncovering prehistoric life. “I’ve found so many dinosaurs that I don’t find them anymore—they find me,” Sereno said.

A paper published in the journal Science on February 19 describes Spinosaurus mirabilis, the first new member of the Spinosaurus genus to be found in over a century. A 20-person team led by Sereno, a professor of organismal biology and anatomy at UChicago, excavated the fossil in Niger in 2022.

According to the paper, S. mirabilis lived roughly 95 million years ago, during the late Cretaceous period. Its most distinctive feature is a tall, scimitar-shaped crest—a bony structure on top of the skull—which the scientists believe was enveloped by brightly colored keratin.

Another defining trait of the species is its dentition: the lower teeth fit between those of the upper teeth, much like those of a crocodile, in what scientists call an interdigitating pattern. This jaw structure is common among fish-eating animals.

While other spinosaurids have generally been found in coastal areas, leading scientists to believe that they were aquatic, S. mirabilis is believed to have lived in an inland habitat with river sediments. Sereno hypothesizes that the dinosaur was a “shoreline hell-heron,” spending its days wading in shallow rivers to hunt fish, rather than being a deep-sea diver.

The discovery marks a major addition to the fossil record of the spinosaurid family. “No one had found enough parts of a skull to reconstruct the whole snout of the animal—nobody,” Sereno said.

Sereno told the Maroon in an interview that the expedition originated from a 1966 monograph in which French geologist Hughes Faure described his 1950s fieldwork in Niger. Faure had reported coming across a fossilized tooth in the desert resembling those of the Carcharodontosaurus species and marked the location on an old map without additional figures or photographs.

“That tooth and that dot on the map sent me back there,” Sereno said.

In 2019, the map led Sereno and his team to the center of the Sahara in Niger. “We get to the spot, and it’s completely flat and barren—nothing all the way to the horizon,” Sereno said.

After driving around the area and scanning carefully for objects, they finally encountered an area with dozens of Carcharodontosaurus teeth.

“It’s a game of visualization,” Sereno said. “You have to interpret a knob and see a dinosaur.”

After collecting about 30 teeth, Sereno prepared to leave, content with his findings. Back at camp, however, a local Tuareg man approached the team and offered to take them to a site further out in the desert where he claimed to have seen fossil bones. According to Sereno, they questioned him carefully and ultimately decided to follow him.

“After a day and a half, we were beginning to panic [and were] running out of gas, but then he drove us, almost like an arrow, up to this gigantic skeleton,” he said. “It was black, and the femur was bigger than anything I’d ever seen in all my 30 years in this field.”

Sereno and his colleagues collected what they could, including teeth, jaw pieces, and what they later realized was the base of a crest, not immediately realizing the significance of their discovery. After years of delays during the COVID-19 pandemic, the team returned to the site in 2022, where they confirmed the discovery of a new species of Spinosaurus, which they named Spinosaurus mirabilis, after a Latin word meaning “astonishing”.

“We went back, and the rest is history,” Sereno said. “In an hour, it all fell into place. It was so overwhelming that there were team members crying.”

Back at Sereno’s Fossil Lab in Chicago, his team scanned the teeth and bones to create a digital rendering of the skull.

Two replicas of S. mirabilis based on that digital rendering are currently displayed at “‘Unicorn’ Spinosaurus Discovered!”, an exhibit by the Fossil Lab at the Chicago Children’s Museum. Sereno arranged for the replicas to be displayed as part of his goal to “take this [discovery] from the cover of Science to the kids of Chicago.” The exhibit will be on display through September 14.

“It’s going to be wonderful to see children dragging their parents to see this amazing thing. This is part of the thrill of working and making your science available,” Sereno said. “Seeing it do something.”

Beyond Chicago, Sereno is also working to help establish the Museum of the River, a new national museum in Niamey, the capital of Niger. He hopes that the project will help showcase the country’s rich archaeological and paleontological heritage and “celebrate something that Niger has for the world.”