Big Bend is rich in fossils. Probably the most famous and awesome is that representing a winged creature called a Pterosaur. This extinct dinosaur weighed about 150 pounds and had a 36-foot wing span. In other words, the distance from one wing tip to another was about the same as the height of a four-story building. Like a huge bat, the Pterosaur had wings consisting of sickle-shaped membranes attached to one long finger on each hand.
This flying reptile had no feathers. Its body was probably covered with fur. It had no teeth. Its neck was disproportionately long, much like that of a modern-day giraffe.
According to the National Park Handbook, “Splashing about in the freshwater were amphibious and semi-aquatic species. Probably commonest was the duckbill dinosaur, an enormous reptile that walked on huge hind legs. It has as many as 2,000 teeth. Specially adapted for grubbing up and munching freshwater plants, these flat grinders occurred in batteries in the duckbill’s jaw. As a tooth wore out, another popped into place.”Other dinosaur fossils, including Allosaurus, Ichthyosaur, and Brontosaurus, have also been found in Big Bend.Before the dinosaurs arrived on the scene in the Cretaceous Period, Big Bend was intermittently underwater. Fossils from this earlier period include oysters, snails, ammonites—a sort of coiled shellfish—and giant clams with shells three feet across. According to the National Park Handbook, “Sea turtles, sharks, and a 9-meter (30 foot) marine lizard that swam in the open ocean have left their remains in the yellowish badlands near the park’s western entrance.”
A more recent fossil, from around 50 million years ago, is that of a small primate. It’s a type of prosimian, dubbed Roonei viayhaensis by its discoverers. This creature lived in the trees near Mariscal Mountain; although at that time, the mountain may have been just the beginning of a little rise in the land. At that time, that area was probably covered with broadleaf evergreen forests, tropical forests more akin to those in Central America than to what you’ll see in the Chihuahuan desert today.
But fossils aren’t all that remain of Big Bend’s ancient life. The Rio Grande river is still home to garfish and turtles that lived here 50 million years ago.