Although dinosaurs are clearly reptiles, there has been a tendency in recent years to recast their biology and physiology as birdlike or mammallike. The scientific case for warm-blooded dinosaurs was presented in a series of publications beginning in 1971. In 1974, there were proposals for the scientific community to recognize the Dinosauria (including dinosaur descendants, the birds) as a class separate from the reptiles from which they were derived. This has led to confusion in popular literature as to whether or not dinosaurs were actually reptiles.