The Dinosaur in the Warehouse
A fossil discovered in 1932 was ignored for decades. Now, it’s revealing how gamebirds evolved in an ancient America. How did it go overlooked for nearly a century?
When you’ve waited millions of years to be discovered, what’s another century of waiting?
That’s the story of Centuriavis lioae, a fossil bird described by Daniel Ksepka and his colleagues in the Journal of Paleontology this October. Centuriavis was a chunky, ground-dwelling bird that lived 11 million years ago. Ksepka didn’t find this fossil underground, however; he found it in the backrooms of the American Museum of Natural History.
The bird had been gathering dust on a shelf since being unearthed in Nebraska in 1932. Until Ksepka took interest, no one had given it a proper look. Now, it is shaping our understanding of gamebird evolution and revealing what life was like millions of years ago.
“I assumed when I looked at it that it was already described, just because it was such a nice specimen,” Ksepka said. He was an associate researcher with the AMNH at the time, poking around the museum’s collection when he stumbled upon the fossil. “I was like, ‘This is so beautiful’,” he said.
Even after finding this fossil, it took Ksepka more than a decade to have enough time to study it. In 2022, as curator of the Bruce Museum in Greenwich, Connecticut, he described it and named it Centuriavis lioae: Centuriavis, or “century bird” for how long it had waited to be studied, and lioae in honor of Suzanne Lio, the managing director of the Bruce Museum.
Bird fossils like Centuriavis are incredibly rare. While mammals have thick bones and solid teeth that hold up well over millions of years, birds’ hollow bones and keratinous bills degrade quickly. Miraculously, this fossil had a tail, collarbone, wingbones, and a skull. The skeleton’s completeness helped the researchers identify what this animal was: an ancient version of modern-day gamebirds like turkeys and grouse.
“It’s probably representing the ancestral lineage…that gave rise to these big, charismatic gamebirds,” Ksepka said. Centuriavis is not quite an ancestor of turkeys and grouse, but rather represents an ancient branch on the gamebird family tree. Centuriavis had spiny leg bones like those of turkeys and grouse, but its shoulder blades had hooks on them, which modern gamebirds lack. It seemed like a bird that was one step away from becoming a turkey.
But scientists could discern more about the bird than just its relatives. Its skull was so intact that Dr. Catherine Early from the Science Museum of Minnesota could perform a CT scan on it.
A CT scanner is kind of like a digital deli slicer: it uses x-rays to capture hundreds of cross-sections of Centuriavis’s brain cavity, which Early could then combine into one 3-D image. This model revealed that the bird’s brain had small olfactory bulbs, meaning it had a poor sense of smell and likely relied on its vision. “It probably lived and behaved very similarly to its modern relatives,” Early said.
Ksepka believes this fossil holds one more piece of information: how Centuriavis mated.
The 1932 expedition that found this fossil also turned up some similar, smaller bones, which Ksepka thinks belonged to a female Centuriavis. In modern game birds, when males are larger than female, they are forced to compete for mates with elaborate displays. Male greater sage-grouse inflate their yellow throat sacs, while sharp-tailed grouse perform elaborate dances, all to attract females. It seems that, millions of years ago, male Centuriavis might have done its own strange performance.
That Centuriavis went undiscovered for so many years is not surprising, according to Early. “There’s so much that goes into keeping a museum running…. studying every fossil that comes in on an expedition is not always top of that list.” There are surely many future discoveries in the backrooms of these facilities, waiting to change our understanding of the past.
“Fossils…give [us] an idea of diversity that existed in earlier slices of time,” said Edward Braun, a molecular biologist at the University of Florida. Nebraska was a very different place 11 million years ago. It was hot and arid and full of rhinos and camels. But in this foreign landscape, the relatives of some of the most quintessentially American birds made their home. Without fossils like Centuriavis, we would never have known what our world once held.
