Are dinosaurs reptiles or birds?

Yes, birds are reptiles, but let me explain a bit. Biologists use two types of classification systems, the Linnaean and the phylogenetic. The Linnaean system was developed by Carolus Linnaeus in the 1730's. read more

Many scientists consider birds to be reptiles. Because all birds share a common ancestor – a dinosaur – then many scientists today also consider birds to be dinosaurs! Are Dinosaurs Reptiles: Conclusion. On this page, we’ve looked at how animals are classified, what makes a reptile a reptile, and the evolution of dinosaurs. read more

Dinosaurs (including birds) are quite different from reptiles - they are endothermic, feathery, lay hard-shelled eggs and have their legs drawn in directly under the body, none of which is true of reptiles. read more

So birds aren't just closely related to dinosaurs, they really are dinosaurs! This is what most people mean when they say that birds are reptiles, although technically according to the phylogenetic system mammals are also reptiles. read more