New research reveals that a well-preserved 52-million-year-old bird fossil specimen from the early Eocene of Wyoming, the United States, is from a previously unknown relative of turacos, a group of birds that is presently endemic to sub-Saharan Africa.
Turacos, also known as banana eaters, are brightly colored medium-sized fruit-eating birds.
They make up the bird family Musophagidae, with around 24 currently recognized species.
The ancient relative of turacos, Foro panarium, was originally discovered in western North America in 1982, and named in the 1990s.
However, only now has the fossil been firmly placed in its evolutionary context.
“Foro panarium exhibits an enigmatic mix of anatomical features that has prevented a robust assessment of its affinities,” said Dr. Daniel Field of the Milner Centre for Evolution and Dr. Allison Hsiang from the Swedish Museum of Natural History.
“The fossil not only shows that turacos formerly resided well outside of their present geographic range, but also that early turacos had long legs, suggesting they may have been ground dwelling.”
“All the modern turacos live in trees and have relatively short legs suited for perching on branches,” Dr. Field added.
“The fact that their ancestors had long legs indicates they most likely lived on the ground, suggesting that turacos may have moved into the trees much later.”
This finding ties in with Dr. Field’s recent research into how birds transitioned to tree dwelling following the asteroid strike that killed dinosaurs 66 million years ago.
Dr. Field and Dr. Hsiang used the fossil record and genetic data of modern birds to trace the evolutionary tree of life for these birds.
“It’s a really exciting time to be studying bird evolution. Modern techniques allow us to study 3D scans of fossils in great detail, and sequence large amounts of genetic data,” Dr. Field said.
“This fossil raises almost as many questions as it’s answered — why are the modern descendants of these birds now restricted to the tropics when they were previously found in the Northern Hemisphere too?”
“We think changes in climate might be partly responsible for fluctuations in the distributions of these birds, but need to study this further.”
The research is published in the journal BMC Evolutionary Biology.
Daniel J. Field Allison Y. Hsiang. 2018. A North American stem turaco, and the complex biogeographic history of modern birds. BMC Evolutionary Biology 18: 102; doi: 10.1186/s12862-018-1212-3