What a coincidence - I happen to be reading Exploration Fawcett, the edited personal notes from Col Percy Fawcett's exploration and mapping expeditions in the unexplored jungles of Brazil, Peru and Bolivia, 1906-1925. As you know, Fawcett, a meticulous observer of facts, not only killed and measured a 62-foot long Anaconda on the Rio Abuna in 1907, but also later reported what he identified as a Diplodocus in the Beni swamps of Madre de Dios, having observed the living animal and its three-toed tracks. Was Fawcett just a kook wandering in the jungle? No, he was a British army officer, professional surveyor, cartographer and Fellow of the Royal Geographic Society, whose job it was to establish the legal boundaries between the three countries in the Amazon headwaters country. One peek at the exquisite official maps he prepared during this period reveals the work of a very capable hand.
That's not to say Fawcett wasn't trashed by his contemporaries for his surprising claims, but the fact remains he is generally accepted as more than a credible witness. [His obsession with the Lost City of Z and his unexplained disappearance are also ammunition for character assassins, but those topics are best discussed elsewhere]
Of course, the early 20th century existence of Diplodocus (or Apatasaurus) in South America was also attested to other explorers by numerous native witnesses, but since these are merely jungle savages, I guess we can ignore their testimonials. Right, Joe?
Is Diplodocus extinct? Most likely. Was it 150 million years ago, or 100 years ago with the settling of the Amazon headwaters? Damned good question. If the latter, then maybe the Tucson sword image isn't a slam dunk game killer, but a strange anomaly. I've tended to ignore these artifacts in the past, but I'm thinking we don't have a consensus regarding their provenance.
That said, I see nothing to support the Superstition Mountains fairy tales that this forum's Oz advocate has tacked on to the Tucson items.