Researchers may have evidence that reveals the origin of the face.
A research team revealed a series of fossils that documents the "step-by-step" development of the face, an Uppsala University news release reported. The fossils show how vertebrates transformed from "jawless" to "jawed" creatures.
A 410 million-year-old armored fish named Romundina is at the heart of this series. The only jawless vertebrates left today are lampreys and hagfishes; there are about 50,000 vertebrates with jaws, including human beings.
"It is known that jawed vertebrates evolved from jawless ones, a dramatic anatomical transformation that effectively turned the face inside out," the news release reported.
When jawless vertebrates are in the embryo stage blocks of tissue develop on either side of their brains. They meet in the middle to form a "big upper lip" that surrounds a lone nostril in front of the eyes.
Embryonic jawed vertebrates have the same tissue, but it grows forward in the midline below the brain and pushes the nasal sacks to either side. If this did not happen our nose would just be a single hole in the center of out faces.
Until now researchers knew very little of the development of this type of face. The Romundina, wich was an armored fish found in arctic Canada, had two nostrils that sit far back, similar to a jawless creature.
"This skull is a mix of primitive and modern features, making it an invaluable intermediate fossil between jawless and jawed vertebrates," Vincent Dupret of Uppsala University, one of two lead authors of the study, said in the news release.
The team imaged the ancient creature's skull at the European Synchrotron Radiation Facility using X-rays.
Jawed vertebrates have a longer front part of the brain than those without jaws; that causes the nose to be positioned at the front of the face instead of far back and between the eyes. The team found the Romundina's brain had a short front end resembling a jawless vertebrate.
"In effect, Romundina has the construction of a jawed vertebrate but the proportions of a jawless one", says Per Ahlberg, also at Uppsala University and the other lead author of the study; "this shows us that the organization of the major tissue blocks was the first thing to change, and that the shape of the head caught up afterwards," Dupret said.
The researchers were able to map out the transition by putting the Romundina in the series. The series ended with a modern vertebrate face.
