Deadly Nadder

A Deadly Nadder (Psittacodracus Ingenus) is an extinct species of bipedal dragon and one of the only known dragons, along with the Hideous Zippleback, of post-KT Earth to have only two legs and two wings, probably having some forms of mutations disappearing from its six-limbed ancestors. Like all dragons, it was carnivorous and mainly fed on wide variety of terrestrial prey items as well as fish. It was about the size of an elephant yet much lighter in weight due to hollow bones, so, along with its well-developed wings and flight bladder, allowed it to fly. It had a spiky tail, which probably shot out of its tail against predators or for hunting prey items. Their fire breath was the hottest in the dragon world, being about half as hot as lava.

Extinction
Despite having flourished in most of the Pleistocene, their habitats were being destroyed by human farmers for the farmer's livestock. Due to having hunted livestock, human knights and vikings killed off the Deadly Nadders.

However, just like some dragons, Deadly Nadder sightings in modern times continues, even though they're still considered cryptids.