The evolution of the face isn’t something many people stop to consider often. We take for granted one of the most important and defining features of not only our species, but also most recognizable species of today’s world.
French and Swedish scientists have teamed up and published a study online in Nature, which examines the origin of the face. They hypothesized that the first step in evolving the face was the evolution the jaw. To unravel the beginnings of the face they looked at a 415 million year old fish.
Romundina is an ancient fish that was about 8 inches long. It was completely armored and had a small spine on its back for additional defense. This fish flourished in the late Silurian and Devonian periods and disappeared about 360 million years ago. Jaws were present in this fish, but instead of teeth the fish had plates used for crushing small crustaceans and other invertebrates like worms.
Using powerful X-rays to view the fossilized remains of this animal, researchers were able to create a 3D model of the specimen. Through analysis of the internal skull anatomy of Romundina, the team proposed that evolution of a jawless animal to a jawed animal with a face occurred in three steps. The first step was the transition from a single nostril that opened all the way under the brain to a double opening on the front of the face and a solid plate under the brain. This step was demonstrated by the Romundina specimen – indicating that it was one of the initial transitional organisms.
The second step is evident in more evolved armored fishes. This step involves the movement of the nostrils to right above the upper jaw. The third and final step is characterized by a lengthening of the face and increased size in the foremost area of the brain. Even though Romundina only represents the first step in the evolution of a face, Vincent Dupret, one of the researchers who worked on the study, comments, “When you look at Romundina, it’s like looking at yourself in the mirror, but with a 415 million year old image… It’s your ancestor.”
Source:
Dupret, V., Sanchez, S., Goujet, D., Tafforeau, P., & Ahlberg, P. E. (2014). A primitive placoderm sheds light on the origin of the jawed vertebrate face. Nature. doi:10.1038/nature12980
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