To save myself time, just gonna link this:
Bogleech: Dragons (2013)

So you could just look at that and see the images. Notice how Dragons have gone through an "image adjustment", just like Unicorns. Whereas Unicorns started out as just ordinary bovids who happened to have one central horn, Dragons seem like an inversion of the Unicorn's case. The two are often mentioned together, in reference to "legendary things that are spoken of as if they were once real back in medieval castle days, and today they're regarded as jokes". The dragons however, were probably chimeras. From labs, not created species.

It's said that reptiles just grow indefinitely, and some suspcious hybrid mammals (which I've never seen IRL, only photos and articles full of 33 orange and baffos) are said to do the same, like Tigons. Old depictions of dragons aren't always reptilian in nature. "Dragons" was probably a catch-all term for a variable "family" of chimeras that were made with genetic meddling (however that was done, probably with blood, not rainbow-magic-spiral dicks n ass) that just got out and terrorized the place. Imagine what a HOUSE CAT can do in Australia or some small island. Imagine what harm rabbits and rats cause when they end up someplace that's not ready for them. Imagine what a dragon could do.

They probably were non-reproducing, and they were said to be obsessed with hoarding shiny objects. They were probably really smart. Dogs, monkeys, and pigs are chimeras, you know. Human/wolf, human/boar, human/lemur. Why do you think those "animals" are so anomalous, even if they're commonplace and people don't give them a second thought.

The image and reputation of the Dragon, has shifted from some foul, unnatural THING that shouldn't exist, that could be wyrms, wyverns, hexapods, or drakes (tetrapods). Some were mammalian, others birdlike, many were reptilian. Probably also some invertibrate-based dragons out there, too. There's no way those things could reproduce, so it's easy to see why they'd all be gone by now. Pop culture today has given Dragons a makeover. You'll notice how Hollywood and mainstream media will glorify things like witchcraft, or being a freak, and of course the moral of ALL their stories is "fame, money, popularity are super good". Even if they try to make a "see, it's okay to be a slave pleb in low standing, it's okay to be poor" message to pump out at the lower classes to watch on TV, or on Youtube or whatever. Anyhow. Can you think of a certain group of people that everyone IRL bashes on them, they're traditionally hated by all, but MSM paints them all as saints and noble? Hmmmm.

So yeah. Created before the Great Flood, many chimera monsters terrorized the people, animals, and environments, and were slayed by heroes. They don't make those things anymore, but now we have Giraffes and fursuits, and severely inbred human-chimeras.