Ancient Hippo Tracks
Researchers in Kenya have uncovered fossilized animal tracks, which they believe may have been left by swimming hippos 1.4 million years ago.
Bottom-Walker
Recent excavations in the Koobi Fora region near Lake Turkana revealed dozens of animal tracks. A majority of the prints, like the one shown here, appear to have been left by a four-toed animal "bottom walking" in a shallow water body, the researchers say.
Toenails
Toenail marks were visible in some of the tracks. The central two toes are more prominent in hippos, and these digits may have scratched at the lake bottom during swimming.
Swimming Hippos
For a modern comparison, the researchers videotaped two female common Nile hippopotamues (Hippopotamus amphibius) through the side of a glass walled tank at the Adventure Aquarium in Philadelphia in 2008.
Hippo Feet
Hippos have distinctive feet with four digits.
Gliding Hippo
Underwater, the Nile hippos would glide with their limbs folded beneath their bodies, occasionally pushing off the bottom of the tank with one leg, only making contact with their digits.
Pushing Off
Sometimes, the hippos would thrust upwards towards the water surface using both hind feet placed firmly apart.
