Three Discoveries, Part III: Fossil Color
In the last two posts, we recounted the discovery of the fossil and its feathers hiding in the block. Inkayacu provided one last surprise in the lab. Not only were feathers and skin intact, but the feathers preserved some microscopic structures giving us a glimpse into the color of an extinct penguin.
After finding several different types of feathers, our team carefully removed small samples to explore with Scanning Electron Microscopy. Matthew Shawkey and Liliana D’Alba (working at the University of Akron) and Jakob Vinther (working at Yale University) analysed the microstructure of the feathers and discovered that melanosomes were preserved in some samples. Melanosomes are microscopic organelles that carry pigments. These bean-shaped structures are responsible for generating certain colors in bird feathers, such as black, grey and red. We have melanosomes ourselves, and they play a role in determining hair color. Different sizes and shapes of melanosomes generate different colors in bird feathers, so by measuring the dimensions of the fossil melanosomes, team members were able to estimate the color these fossil feathers would have been in life. Reconstructions of samples from the feathers on the underside of the flipper support a reddish-brown hue, while isolated body contour feathers found in the block of rock encasing the penguin skeleton appear to have been colored grey and reddish brown.
Finding evidence for these colors was unexpected, because most living penguins are black and white. This is a good color scheme for an aquatic predator, because the white underside makes the animal harder to see from below and the black back makes it harder to see from above. A black and white countershaded pattern is employed by many other animals that hunt underwater, such as Razorbills (auks), Killer Whales, and many sharks. We don’t know the entire color scheme of Inkayacu because we only have wing feathers and a few body contour feathers to study. Because the contour feathers were loose in the sediment, we can’t tell whether they were from the front, back or side of the bird. Still, the presence of reddish brown feathers on the underside of the wing suggests an unusual color pattern, perhaps foregoing the standard countershading to create a more seal or dolphin-like solid outline.
It is interesting to note that brown and grey colors do characterize the hatchlings and juveniles of some penguin species. For example, King Penguins in their second molt look like big brown piles of leaves. This raises the question of whether the first specimen of Inkayacu is actually an immature individual. So far, that seems to be unlikely, because all of the bones have a finished texture and elements that remain separate in young birds are fully fused together in the Inkayacu specimen. This evidence strongly supports adult status.