The specimen remained at a Russian museum for years until, approximately one and a half years ago, the museum organized a traveling exhibit that came to the University of Kansas Natural History Museum. Martin specifically requested that they bring along Longisquama.
Martin and his coauthors pored over every detail of the fossils, which included most of the skeleton except for the hind end, and impressions made by the skin. The scientists found three key clues that convinced them that the structures along the animal's back were feathers instead of scales.
First, the appendages showed some of the most recognizable features of a modern-day feather. The scientists identified a long, thin tube called a "shaft" running down the center of each appendage. A short distance from the base, a dense row of fine strands called "pinnae" project from either side. Neither the shaft nor the pinnae are typically thought to be features of reptilian scales. The shaft also comes to a point at the base and appears to poke into a follicle in the skin. In contrast, modern scales form in continuous sheets.
The Science authors also discovered that the base of the shaft was divided into several subsections, which is thought to be a signature of the complex developmental patterns unique to feathers.
The third clue also indicated that the appendages followed the same growth pattern of modern feathers. The pinnae of modern feathers first develop inside a tube called a feather sheath and then unfurl as the feather grows. The Longisquama fossil shows a new feather that seems to be developing in the same manner. At the base end, the entire structure is preserved and only the surface of the outer wall is visible. Nearer to the center, the wall is broken off, exposing the pinnae inside. Further toward the tip, the pinnae seem to have flaked off, and the wall of the op
Contact: Heather Singmaster
American Association for the Advancement of Science