Picture a catfish. Now try to picture a catfish that's 5 feet long. Once you have that, try to picture a catfish that's 5 feet long and lives in the Sahara Desert. Such a creature did exist there, though it was 50 million to 100 million years ago when what is now one of the most arid places on earth was under water, reports the Guardian. Archaeologists have uncovered a slew of fossils from the desert in northern Mali showing that the region was not only teeming with sea creatures, it was teeming with big sea creatures. In addition to the huge catfish, 40-foot-long sea snakes and 4-foot-long bony fish known as pycnodonts thrived, specimens far larger than their modern-day counterparts. Back then, what is now the Sahara looked more like Puerto Rico, with a sea that covered more than 1,150 square miles at a depth of about 160 feet.
"Fossils found on the expeditions indicate that the sea supported some of the largest sea snakes and catfish that ever lived, extinct fishes that were giants compared to their modern day relatives, mollusk-crushing fishes, tropical invertebrates, long-snouted crocodilians, early mammals and mangrove forests," says lead researcher Maureen O’Leary of Stony Brook University in a release. She also talks about the expeditions and shows off fossils in this video. So why did the creatures get so big? In their paper in the Bulletin of the American Museum of Natural History, the scientists note that the "Trans-Saharan Seaway" was isolated from other major seas, which seems to have led to the phenomenon of gigantism typically associated with animals on remote islands. (It's possible an ancient Saharan river system could flow again someday.)