Fossilized Giant Penguin Feathers Reveal Color, Feather Structure of Ancient Birds

A North Carolina State University researcher is part of a team that has discovered fossilized feathers from a giant penguin that lived near the Equator more than 36 million years ago. These feathery fossils reveal color patterns in an ancient extinct penguin species, and offer clues to how modern penguin feathers evolved.

The penguin in question – dubbed Inkayacu paracasensis, or Water King – dates from the late Eocene period and stood almost five feet tall. The fossil was discovered near the Paracas Reserve, located along the eastern coastline of Peru. A research team led by Dr. Julia Clarke from the University of Texas at Austin, which included scientists from NC State, Yale University and the University of Akron, discovered the feathers while preparing the specimen.

The researchers’ findings appear in the Sept. 30 edition of Science.

“We recovered feathers still attached to the wing, as well as some smaller body contour feathers, which in modern-day penguins serve to waterproof them and regulate their body temperature,” says Dr. Dan Ksepka, NC State research assistant professor of marine, earth and atmospheric sciences, research associate with the N.C. Museum of Natural Sciences, and co-author of the paper. “In terms of size, these feathers are really no larger than the ones you would find on a ‘normal-sized’ penguin; in fact, some small modern penguins’ feathers are longer than the ones on this animal.”

By looking at the fossilized feathers’ melanosomes, tiny pigment-carrying structures within cells that give bird feathers their hues and our hair its color, team members from Yale and Akron determined that unlike modern penguin feathers, which are predominately black and white, I. paracasensis feathers were a softer gray or reddish-brown color – shades associated today with penguin babies, not adults.

“Some of the feathers we found were loose, so we can’t totally ‘color in all the lines’ on the penguin yet, or tell which feathers may have been part of a brighter display pattern on the bird, like the eye and neck bands on some modern species of penguin,” Ksepka says. “But features of the bones tell us that this particular fossil was a fully-grown adult, not a juvenile, so finding brown and gray colors was a surprise.”

The researchers also found that the fossil’s melanosomes were much smaller than those found in modern penguins, leading to questions about how and why penguin feathers changed over time.

According to Ksepka, “The fossil record shows us that Inkayacu and other giant penguins were very successful during the Eocene – they ranged all over the Southern Hemisphere. But for some reason, they didn’t continue to thrive into the present, and all of the giant penguins are now extinct. By looking at the way these fossilized feathers differ from those of living penguins, we may be able to learn more about why species like Inkayacu became extinct, while the smaller modern species continue to survive today.”

The research was funded by grants from the National Science Foundation and National Geographic Society. The Department of Marine, Earth and Atmospheric Sciences is part of NC State’s College of Physical and Mathematical Sciences.

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Note to editors: Abstract of the paper follows

“Fossil Evidence for Evolution of the Shape and Color of Penguin Feathers”

Authors: Julia Clarke, University of Texas at Austin, Daniel Ksepka, North Carolina State University, Matthew Shawkey, University of Akron, et al.
Published: Sept. 30 in Science

Abstract:
Penguin feathers are highly modified in form and function, but there have been no fossils to inform their evolution. A giant penguin with feathers was recovered from the late Eocene (~36Ma) of Peru. The fossil reveals that key feathering features including undifferentiated primary wing feathers and broad body contour feather shafts evolved early in the penguin lineage. Analyses of fossilized color-imparting melanosomes reveals that their dimensions were similar to those of non-penguin avian taxa and that the feathering may have been predominantly gray and reddish-brown. By contrast, the dark black-brown color of extant penguin feathers is generated by strikingly large, ellipsoidal melanosomes previously unknown for birds. The nanostructure of penguin feathers was thus modified after earlier macrostructural modifications of feather shape linked to aquatic flight.