In 1902, the first T-rex skeleton was exhumed on a dig led by Barnum Brown, an eccentric — albeit brilliant — scientist who also sat as the senior paleontologist at the American Museum of Natural History.
The T-Rex's fossilized remains were quickly shipped to the AMNH, where they were first displayed (pictured up top), and later tucked away into storage as newer, bigger T-rex specimens were discovered. For years, the dismantled skeleton remained hidden away — each individual bone labeled with the number "973" — until 1941, when Brown sold the completed skeleton to the New York museum's biggest rival - the Carnegie Museum in Pittsburgh. Or at least, that's what everyone thought happened.
Because as it turns out, the Carnegie Museum had actually paid for an incomplete specimen; the T. rex that arrived in Pittsburgh was missing a rib bone featured in the AMNH's original collection.
Since it was just one bone from an otherwise whole skeleton, the missing piece went unnoticed for almost three-quarters of a century, and likely would have gone overlooked indefinitely had a young researcher named Thomas Carr not happened upon it while rummaging through the back rooms of the AMNH.
Carr recently recounted his discovery to NPR's Christopher Joyce:
"When I was going through this process of opening up cabinets and looking through shelves...I came upon this one cabinet." Carr peered inside, and "with unbelieving eyes," he says, he saw some bone fragments. "I knew what it was because of the number, 973..."
You can read more about the history of one of the world's most important paleontological finds, its drawn-out journey from Montana to Pennsylvania, and the long-overdue reunion with its wayward rib bone over at NPR.
Top image via NPR