Birds are vertebrate, warm-blooded, walking, jumping or maintained only on the hind limbs while the forelimbs are modified as wings, like many other anatomical features, are adaptations for flying, but not all fly. Their bodies are covered with feathers and today's birds, a toothless horny beak. To reproduce lay eggs, which hatch to hatch.
The taxonomic group called for the systematic class Aves classic but current phylogenetic systematics this clade has no range, and is included to turn on within clades: Theropoda, Dinosauria, Archosauria, Sauropsida, Tetrapoda, etc., but more nesting intermediate term.
The birds originated from bipedal carnivorous dinosaurs of the Jurassic, 150-200 million years ago. Its subsequent evolution resulted, after a strong radiation at about 10,000 extant species.
