Three Discoveries, Part II: Feathers!
Continuing the story of Inkayacu, we find ourselves in the paleontology lab back in Lima. After being carefully excavated, plastered and transported back to the museum, Pedro the fossil penguin needed to be soaked in water. This helped protect the fossil from the rapid change in environment. After spending several million years in one of the most arid environments on Earth, the fossil was suddenly going to be exposed to the humid airs of Lima. This could spell bad news for the fossil, because salts concentrated in the rock long ago would rapidly expand with moisture – the growing crystals could literally pop the fossil bone apart with tiny fractures, as has happened to desert fossils before. To prevent this, the team soaked the block for several days to draw the salts out into solution, rather then letting them form crystals. Afterwards, the marathon of preparing away the rock could begin. Walter Aguirre of the Museo completed many of the bones, and the US team including Dr. Julia Clarke and students Drew Eddy and Adam Smith (then at NCSU, now at UT Austin), along with Dr. Paul Brinkman and Vince Schneider of the North Carolina Museum or Natural Science traveled several times to join in.
Late into the evening, our team worked in the preparation station of the Museo de Historia Natural painstakingly removing bits of rock matrix from the bones of the penguin using tools like dental picks and needles set in pin vices. Up to this point, we were not sure whether there would be any other soft parts preserved with the skeleton but we proceeded carefully nonetheless, to avoid a careless scratch to the fossil bones. I remember clearing bits of siltstone away from the femur when the moment of revelation came. Julia Clarke flipped over a thin sheet of rock, and there underneath was a spectacular row of wing feathers.
The feathers were so exciting beause they offer our only glimpse into the transition between the normal flight feathers possessed by the flighted ancestors of penguins and the highly modified, scale-like feathers ofmodern penguins. Most living birds have about a dozen large primary flight feathers attached to the bones of the wing tip, but living penguins have several times as many small, stiff feathers in this region, covered by muliple rows of nearly identical scale-like feathers. The rachises, or quills, of the feathers are widened and flattened as well. This helps create a short, stiff flipper – terrible for flying through the air but perfect for propelling the bird through the water.
As preparation of the block continued, we came upon feathers from other parts of the body loose in the matrix. These feathers are body countour feathers, the feathers that help insulate and waterproof the penguin. Several body countour feathers were found near the bones of the leg, but we cannot be sure exactly where they came from because they are no longer attached. These feathers were interesting because of their size. Nearly complete examples measure about 3cm long, which is actually a bit shorter than the feathers of many smaller living penguin species. Possibly, the length of the feathers is related not only to overall size but also to habitat. Playing into this idea, some small Antarctic penguins have countour feathers about 50% longer than those of Inkayacu, which lived in a tropical environment.
The feathers had one more secret in store, and we will cover that in the next post.