The Kasai Rex is a gigantic therapod cryptid from the Democratic Republic of the Congo. It is said to be a surviving theropod dinosaur, such as Tyrannosaurus rex, though it has also been depicted as a huge monitor lizard as well as a terrestrial crocodile.
In 1932, Swedish plantation owner John Johnson (sometimes spelled Johanson) was traveling with a servant in the Kasai Valley. They encountered a rhinoceros and tried to avoid detection when a large creature rushed from the undergrowth and attacked the rhino. Johnson fainted and the servant ran away. When Johnson recovered, he saw the creature eating the rhino.
"It was reddish in color, with blackish-colored stripes," he said later. "It had a long snout and numerous teeth." He decided that the creature, 13 m (43 ft) long, was aTyrannosaurus, and also said "The legs were thick; it reminded me of a lion, built for speed".
However, no tyrannosaurs were known to live in Africa, but one theropod similar to the size report and lived in Africa is none other than the Carcharodontosaurus saharicus. Carcharodontosaurus was the apex predator of Early Cretaceous Africa, and was also known to compete over food with Spinosaurus aegyptiacus.
Note: I decided to go with a T-Rex design for the Kasai Rex. I based its colors of the the T-Rex in the Jurassic Park novel.