Three testimonials of sightings exist that took place near the Dongu-Mataba (tributary of the Ubangi River) in the Republic of the Congo. The first one was in 1961; the second ten years later in 1971 by pastor Joseph Ellis. He estimated the length of the (visible) tail-part as 10 meters (32 feet) long (equal to his dugout, no neck or head could be seen), and a diameter of 0.5 to 1 meter. It was described as being grayish-brown. Back in the village, it appeared that the subject was taboo. These and other sightings were gathered by University of Chicago biologist Roy P. Mackal, who led two expeditions to the Likouala swamps in the Republic of Congo, while searching for the Mokele-mbembe. Mackal concluded that the animal has a low-slung body, and therefore is more like a lizard than a snake, as "Ellis was positive the animal never raised itself sufficiently after leaving the water". Mackal also noted that the animal's triangular- or diamond-shaped ridges were similar (but smaller) than those from the Mbielu-Mbielu-Mbielu. This is a common misreading from his book and mixed up at a lot of webpages. Possibly the same animal is described in the 1958 book On the Track of Unknown Animals by Bernard Heuvelmans. In 1928 a snakelike animal called Ngakoula-ngou or Badigui was reported in the Ubangi-Shari area. This report was made by game inspector Lucien Blancou, who later in 1954 also first reported the Emela-Ntouka.According to this report, it killed a hippo in the Brouchouchou river without leaving any sign of a wound. It also crushed a manioc field, leaving tracks 1 to 1.5 meters wide. Similar reports from 1932 (at Bouzoum) and 1934 exist, in which it is called Diba, Songo, Mourou-ngou and Badigui. In the 1934 report, an old man had come to see Blancou, as he was told that he showed interest in the animal. The old man narrated that in about 1890 he was fishing in the Kibi stream (Bakala district), and saw the Badigui eating from a tree, called "roro". He described the neck to be "as thick as a man's thigh", and the underneath of the neck was lighter colored. He could not see the full body, only about 8 meters of the neck. He also said "it does not frequent places where you find hippos, for it kills them". Finally in 1945, the animal's tracks were spotted near Ndélé, by Blancou's gun carrier.
It is believed by some people to be a living dinosaur, most likely a spinosaurid; a genera of rather gigantic crocodile-like theropods that dwelled on riverside, rainforest; coastal and delta habitats, that hunted any prey item available. If Nguma-Monene is a giant member of the spinosaur family this would be an amazing discovery. Nguma-moneme also described to be quite similar to the early land animal/Synapsid; Dimetrodon. It has also been said that it may be an elongated member of the varanidae family, the monitor lizards.
Others suggest the claims are merely misidentifications or heavily exaggerated, and instead simply represent modern crocodiles or nile monitor lizards.
The Badigui sighting may refer to a creature similar to Mokele-mbembe, not Nguma-monene. This is because Mokele-mbembe kills hippos and is a vegetarian - the Mokele-mbembe is said to eat from a type of liana-like plant called malombo.