QUOTE(wcturnersr @ Oct 25 2005, 09:11 PM) [snapback]902532[/snapback]
Dinosaurs were not reptiles... and I do believe that they were warm-blooded.
Way back when, sometime around 370 mya, give or take, the amniotic egg evolved, which allowed life to reproduce on land, unlike amphibians, who needed to lay eggs in water. These first amniotes had simple, box-like skulls with only openings where they were needed for eyes, nostrils, etc, and were called anapsids. (There's a raging debate about whether turtles are surviving anapsids or not, but I'll not bother with that. However, if turtles are not anapsids, the anapsids are now extinct.)
Eventually, the anapsids produced two new lineages, each of which had extra holes in their skulls, which served to lighten them and to provide additonal sites for muscle attachment. One group had a single hole, th synapsids, and they evenually became mammals. The other group, diapsids, had two holes, and these have a more interesting history.
The Diapsids split again into two groups. One, the lepidosaurs, are modern snakes and lizards. The other is called the Archosaurs, or "ruling reptiles", and for good reason. This group has evolved into some of the most successful and frightening predators ever, including the rauisuchids, ornithosuchids, popsaurids (all 3 of which would best be imagined as giant, fast-running land crocodiles, often over 20 feet long), crocodiles, phytosaurs (similar to crocs, but with a nostril near their eyes rather than at the tip of the snout), pterosaurs, dinosaurs, and birds.
So, technically, dinosaurs weren't lizards, but they *were* reptiles, close cousins of the crocodile and ancestors of the bird.