The Ostriches of Wyoming

Small as a chicken, this fossil ratite shows exquisite preservation and new puzzles for evolution.

There may be living ostriches in Wyoming zoos, but not many ones made of stone. This fossil from the Green River Formation is said to be 50 million years old, but its discoverers link it with flightless ostriches on the other side of the world. Science Daily says,

The bird fossils were found more than a decade ago, completely intact with bones, feathers, and soft tissues in a former lake bed in Wyoming. Nesbitt cannot hide a grin as he calls the fossil a once-in-a-lifetime discovery for paleontologists.

Sterling Nesbitt is the main guy behind a paper on this fossil. What does it tell him about evolution? For one thing, Africa and the Middle East are not the only playgrounds for large, flightless birds. And it lost its flight not long after the extinction of the dinosaurs in the evolutionary timeline.

“The new bird shows us that the bird group that includes the largest flightless birds of today had a much wider distribution and longer evolutionary history in North America,” Nesbitt said. “Back when Calciavis was alive, it lived in a tropical environment that was rich with tropical life and this is in stark contrast to the high-desert environment in Wyoming today.”

The Calciavis skeleton will be important to interpreting new bird fossils and other fossils from the Eocene epoch that were collected decades ago. “This spectacular specimen could be a ‘keystone’ that helps interpret much of the sparse fossil of birds that once lived in North America millions of years ago,” said Nesbitt.

A paper by the American Museum of Natural History describes it in more detail. The abstract mentions another evolutionary conundrum:

Thus, regardless of the position of Tinamidae, Lithornithidae is recovered at the base of the clade. However, evidence that many, if not all, of these “ratite” lineages independently evolved similar morphologies related to large size and flight loss suggests that the proposed position of the Lithornithidae remains tentative.

Tentative means subject to change without notice pending new discoveries.

Let’s stop the jargon charade. “Calciavis” means “stone bird.” “Lithornithidae” means “class of stone birds.” So StoneBird is a member of the class of StoneBirds. Got it? You, too, can be a scientist. Just learn some Latin and teach a stone to fly.

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