Fossil Reveals Ostrich Relatives Once Lived in North America

by AMNH on

Research posts

New research reveals that 50-million-year-old bird fossil specimens, some of which are on display in the Museum’s special exhibition Dinosaurs Among Us, are from a previously unknown relative of the modern-day ostrich.

Calciavis grandei fossil
A nearly complete skeleton of Calciavis grandei on display in the Museum’s special exhibition Dinosaurs Among Us.
© AMNH/D. Finnin

The study, published recently in the Bulletin of the American Museum of Natural History, is co-authored by Sterling Nesbitt of Virginia Tech and Julia Clarke of the University of Texas at Austin, both of whom are also research associates at the Museum.

“This is one of the earliest well-represented bird species after the age of large dinosaurs,” said Nesbitt of the specimen, which was found more than a decade ago—with bones, feathers, and even soft tissues intact—in a former lakebed in Wyoming.

Calciavis grandei on a grassy lake shore
Artist's rendering of Calciavis grandei by the shores of the Eocene Fossil Lake about 50 million years ago, with a small rallid in the background. 
© V. Simeonovski

The scientists named the new species Calciavis grandei in honor of famed paleontologist Lance Grande, who has studied fossil fishes from the same ancient North American lake for decades.

“The new bird shows us the group that includes the largest flightless birds of today had a much wider distribution and longer evolutionary history in North America,” said Nesbitt.


Lithornithid skull fossil with an open beak
This Lithornithid skull fossil was recovered from the Green River Formation of Wyoming. 
© S. Nesbitt

Included in the extinct group of early Palaeognathae birds, the Lithornithidae, Calciavis grandei is a very close relative of living ostriches, kiwis, and tinamous now living in the southern continents. It went extinct, along with other tropical birds, after North America’s tropical forests disappeared.

“Relationships among species in this lineage of birds have been extremely contentious,” Clarke said. “We hope the detailed new anatomical data we provide will aid in finding a resolution to this ongoing debate.” 

The Calciavis specimen will be important to interpreting new bird fossils and other fossils from the Eocene epoch that were collected decades ago.