Inspiration can come from the oddest places.
Last weekend was my nephew's birthday. My parents brought him a book, one of those pseudo-documentary-style books about dragons. It was actually a pretty well-done variant on the subject for young readers, touching lightly on dragon mythology from cultures all over the world, mostly pointing toward how misunderstanding of dinosaur fossils gave rise to said mythology. But there were some minor references to cryptozoology, as well, particularly a little gem about the legendary article in the Tombstone Epigraph about two cowboys who may have shot a "Thunderbird" back in 1890.
So, of course I promptly went home and did a web search for the article. Apparently it's a well-known tidbit in Fortean circles. There's a well-written, thorough, and recent exploration of the mystery over at Strangemag.com which strongly suggests the whole thing is an urban myth, and of course in the digital age it's almost impossible to suss out--at least at my level of tech-savvy--what's authentic and what's merely mirrored.
The article in the Epigraph seems to be authentic enough; the nice people of Tombstone, Arizona who have a vested interest in promoting the history of the town have digitally scanned in a century's worth of back-issue newspapers, and the article is right there in the April 26, 1890 issue, page 3. Of course, fifty years earlier a major New York newspaper was bamboozling readers for months with stories of the great civilization found on the moon, so I can't put too much stock in the veracity of the story or the cowboys who reported the hunt.
Still, it's a wonderful image--a couple of cowboys encountering a giant flying lizard. I actually have a story planned for later in the Trace saga that was needing something right along those lines, and I didn't want to go with flying vampires or giant bats.