A recent field trip to Niger turned up rivers of fish fossils for evolutionary biologist Robert Laroche to study.
By Mike Williams
Robert Laroche went fishing in the Sahara. The catch was greater than he dared hope.
The fourth-year Rice graduate student mentored by evolutionary biologist Scott Egan spent three months in the desert in late 2022 with an expedition to discover fossils of all kinds. The now-barren stretches of Niger once teemed with life, and the evidence is plentiful if you know where — and when — to look.
“Some [researchers] had been to Niger before,” Laroche says. “The sand dunes move constantly, sometimes at incredible rates, so when they would revisit a site, it would be completely covered, but right next to it, there would be a whole new area with fossils, like litter, all over.”
Guides led the team of several dozen paleontologists, geologists and evolutionary biologists to three regions that required sometimes arduous journeys across the desert in a caravan of vehicles kitted out for extreme conditions. The payoff at the first site was immediate. “At multiple sites we found a huge number of fish fossils preserved in incredible condition,” he says. “When you have multiple specimens of what looks like the same organism, it deepens our understanding of its biology.”
Laroche mainly hoped to find “articulated” fossils of Actinopterygii, ray-finned fish that are ancestors of almost all fish today, and perhaps part of an even-more-distantly related lobe-finned fish, Sarcopterygii, whose relatives evolved into dinosaurs — and us. While most of the trip focused on the bounty of dinosaur bones, Laroche found what he was looking for on rocky outcroppings hidden deep in the desert. There, he found partial skulls of specimens that he believes may belong to the family Polypteridae, freshwater fish that evolved divergently from the rest of Actinopterygii “with a head that was potentially close to a meter long.”
Everything you think of as a fish today, with the exception of maybe one or two species, falls into this one group called ray-finned fish. Polypterids are interesting because they separated from all other ray-finned fish nearly 400 million years ago. There are living species of them today.
According to Laroche, “Everything you think of as a fish today, with the exception of maybe one or two species, falls into this one group called ray-finned fish. Polypterids are interesting because they separated from all other ray-finned fish nearly 400 million years ago. There are living species of them today.”
Tons of sediment, including blocks of sandstone from a “microsite” loaded with fish fossils in Gadoufaoua, which the team visited twice, were arduously bound in plaster, excavated and put on trucks in up to 130-degree heat. Presently still in Niger, they will be shipped to the United States for study before being put on display in museums planned for Agadez and the Nigerien capital of Niamey. “They’ll take years to study,” says Laroche.
Since returning from the trip funded by Rice’s Expanding Horizons Fellowship Program and a Wagoner Foreign Study Scholarship, Laroche has focused on his thesis with the encouragement of his mentors. But he would like to return to the desert one day. “Part of the excitement is knowing that showcasing the diversity of fossils will lead to future expeditions and research.”
Scott Egan is an associate professor of biosciences at Rice.
Learn more about Laroche’s field research at robertaslaroche.com/blog.