Nematonotus is a small to medium sized fish. The characteristic feature of this species (when present) is the first fin ray of the dorsal fin, which elongates to form a spine. The dorsal fin is located slightly anterior to the middle of its basically flat body. The pectoral fins also possess an elongated first fin ray. The pelvic and anal fins are small.
This species was a predatory fish in the Late Cretaceous. It is found only in Lebanon near the villages of Hakel and Hajula. This fish has no living relatives; it died out in the late Cretaceous.
James W. Davis first described Nematonotus longispinus in 1887, under the name Pseudoberyx longispina. In 1903 Oliver Perry Hay reinvestigated the type specimens Pseudoberyx longispina and Nematonotus bottae (first described by Woodward in 1899). In comparing the specimens collected by Professor Day, he concluded that many specimens previously named Nematonotus bottae were indeed the same as the specimens previously named Pseudoberyx longispina. He then concluded that the species longispinus belonged in the genus Nematonotus.
This specimen is nicely presented with the fossil eel Hayenchelys germanus.