informal term for a subgroup of flying reptiles (Pterosauria (pterosaur)) known from the Late Jurassic (Jurassic Period) through Late Cretaceous periods (Cretaceous Period) (145 million to 65 million years ago).

Pterodactyls, or, more correctly, pterodactyloids, are distinguished from basal pterosaurs by their reduced teeth, tail, and fifth toe. Pterodactyloid metacarpals (metacarpal) (palm bones) were more elongated than those of earlier pterosaurs, which instead had elongated phalanges (finger bones). There are also proportional differences in the skull, neck, pelvis, and wing bones. Pterodactyloid genera include Pterodactylus, a Late Jurassic form from Germany with a wingspan ranging from 50 cm (20 inches) to well over 1 metre (3.3 feet). It is likely that all fossils of Pterodactylus represent different stages of growth within a single species. Pteranodon, a Late Cretaceous form found in North America, had a long cranial crest and a wingspan exceeding 7 metres. Other crested genera are found in Late Cretaceous deposits of Brazil and include Tupuxuara, Anhanguera, and Santanadactylus; Dsungaripterus and several other crested forms have been discovered in China. A group of Late Cretaceous pterodactyloids called azhdarchids includes Montanazhdarcho and Quetzalcoatlus from North America, Europe, and Africa. The wingspan of these reptiles ranged from 2 to 11 metres, which makes them the largest-known flying animals.