<skos:note xml:lang="en">The class of vertebrate animals that are typically bipedal and warm-blooded, lay large-yolked hardshelled eggs, often arboreal, and possessing feathers, hollow bones, forelimbs adapted for flight (although some have lost the ability to fly) and hindlimbs for perching and locomotion, a four-chambered heart, keen vision, a horny beak without teeth, and a large muscular stomach. Birds arose from theropod dinosaurs, which were an order of carnivorous dinosaurs.</skos:note>