No one can resist dinosaurs. Even more than dragons (see post from a few days ago), dinosaurs hold our imagination because they were the real dragons - and European and Chinese chroniclers of dragonlore never invented anything more impressive.
Dinosaurs, it is almost universally thought, disappeared 60M years ago following the so-called K-T impact, when the world changed, the dust clouds and cold descended, the dinosaurs died off (not instantly, but pretty quickly in geological terms) and the way was cleared for the ascendancy of mammals and birds. Occasional claims of post K-T dinosaur fossils are written off as mislabeled or reworked from older deposits as land folds, rises, or recedes under the pressures of millions of years' worth of geological processes.
Dr. Karl Shuker, always worth reading on this subject, offered a Top Ten claims of surviving dinosaurs. Some are easy to dismiss: there's no evidence motorists in Chile in 2004 saw velociraptors, or that a "stegosaur" bas-relief carved in Cambodia shows anything except a boring old tapir in front of a bush. Stories from South America and Australia are, in general, sourced from one person, or someone claiming to quote indigenous people who are now long dead. Trying to overturn the dinos-are-dead paradigm with this material is like charging an elephant armed with a broom handle.
The one that pops up as relatively well-sourced is mokele-mbembe, known by several other names as well and described from various places in the Congo River basin in Africa. I say "relatively" because there are some 20th-century sighting reports, and there are some photographs and videos, taken (either unfortunately or expectedly, depending on your point of view) from too far away to show anything useful. Dr. Roy Mackal, who went on an arduous expedition but didn't see the creature, thought it could be a small sauropod or possibly a huge monitor lizard. He wrote an undeniably intriguing book on the subject.
And yet - many expeditions later, we don't have a good sighting by an outside scientist, a good image, any remains of an animal. Paleontologist Louis Jacobs, in the only book on African dinosaurs, ridiculed it, arguing this area is not a "lost world" unchanged since the Mesozoic.
My take? We're not going to find a dinosaur. Not in Africa, not anywhere. I think we are going to find more large land animals, but if we've already seen the best evidence, we haven't seen enough to support anything as science-shattering as living dinosaurs.