Recently, the identification of two extinct bird species — fossils dating from 52 million years ago — revealed telling information about the evolution of perching birds, the most species-rich bird group we know today. They are the feathered friends we typically find in our backyards, like finches and sparrows, and they are distant relatives of the early archaic perching bird group Passeriformes.
Indeed, so important were the findings of this study that they were published in the journal Current Biology in February. Learning of the fossil discovery and subsequent naming prompted a visit to the Bruce Museum in Greenwich during which I met with Daniel Ksepka (November 2015 WAG), a co-author of the paper. Among his fossils and the treasure trove of artifacts and specimens in the storage facility beneath the museum, this affable paleontologist offered me an introduction to his specialty.
Ksepka has a formidable pedigree that includes a bachelor of science degree from Rutgers University, a master of science and doctorate from Columbia University and a stint at the American Museum of Natural History. As a child, he had an early and brief interest in trains, until he became fascinated with dinosaurs. He credits that fascination with starting his journey to paleontology.
Though he has conducted research and taught, Ksepka said, “I always wanted a museum home.” The Bruce, where he is curator of science, has been his home since 2014.
Ksepka’s research has always centered on the evolution of birds — our modern link to dinosaurs. For years, he has collaborated with Lance Grande, a curatorial scientist in the Integrative Research Center of The Field Museum in Chicago — his co-author on the perching bird fossil paper — on countless examinations of the findings from Fossil Lake. This is a fossil-dense body of water, Ksepka said, that encompassed a 60-mile span at its peak and, as part of the Green River Lake System, covered parts of present-day Wyoming, Utah and Colorado.
While it is more common to find fossil fish in this lake — as featured in a past Bruce Museum exhibit, “The Secrets of Fossil Lake” — the fossil bird finding in Wyoming, in its perfect intact form, was indeed something special, Ksepka said. Seeing the specimen, I found it impossible, even as a novice observer, not to notice every detail of this long extinct species.
As reported in the announcement from the Bruce Museum, the two extinct species of perching bird that have been identified are Eofringillirostrum boudreauxi, from Wyoming, and Eofringillirostrum parvulum, discovered in Germany. Ksepka clarified the naming: “The species name boudreauxi is in honor of Terry Boudreaux, who donated the fossil to The Field Museum. It belongs to The Field, but it has been on loan to me for study at the Bruce. “Only a tiny fraction of animals is preserved in the fossil record.”
The reason that specimens from this particular lake could remain intact has to do with the optimum conditions for discovery in its depths, he says. “When you get to the bottom, the water is oxygen-free, so no one scavenges there.”
Without predators, a fallen bird would remain unscathed at the bottom of the lake’s plate and, over this vast period of time, would become fossilized.
What these recently discovered species highlighted was the differentiation in these birds from 52 million years ago to modern times. Their beak formations revealed much about how the species evolved as one that would have sipped nectar, cracked seeds and sought out bugs.
The foot formation in the fossil presented a huge distinction, Ksepka said. The ancient form most likely nested within a tree’s cavity, unlike their modern-day counterparts, which have a variety of nesting strategies. “In the fossil, the first and fourth toes faced backwards and the second and third face forwards, whereas in modern perching birds only the first toe faces backwards.”
Studies such as this one, Ksepka’s 49th scientific paper, “provide us with a historical record of how things changed over time and how ecosystems responded to change.”