(zoology) the cavity (in birds, reptiles, amphibians, most fish, and monotremes but not mammals) at the end of the digestive tract into which the intestinal, genital, and urinary tracts open
extinct primitive toothed bird of the Jurassic period having a long feathered tail and hollow bones; usually considered the most primitive of all birds
an extinct reptile of the Jurassic and Cretaceous having a bird-like beak and membranous wings supported by the very long fourth digit of each forelimb