New Evolutionary Mechanism for Body Elongation Discovered

By examining an especially well-preserved fossil, paleontologists have discovered a new method behind body elongation. The 240-million-year-old specimen from Switzerland further revealed that the fish, known as Saurichthys curionii, was not as flexible as today's eels, or as fast as a tuna.

The physical traits that comprise an elongated body have evolved many times and independently during the past 500 million years, though current wisdom points to one of two sources behind current examples of extreme elongation of the body axis. The first is through the elongation of the individual vertebrae of the vertebral column, and the second through the creation of additional vertebrate.

Using the fossil, the team from the University of Zurich have identified a third mechanism that played a role in the early evolution of fish -- the doubling of the vertebral arches of the axial skeleton.

According to Erin Maxwell, a post-doctoral student and co-author, "This evolutionary pattern for body elongation is new. Previously, we only knew about an increase in the number of vertebrae and muscle segments or the elongation of the individual vertebrae."

This discovery was made possible through the fortunate fact that the tendon and tendon attachments surrounding the animal's muscles survived, in addition to the skeletal parts. Based on their shape and arrangement, the researchers were also able to determine how flexible the fish was and how well it swam. The animal, according to the scientists, was not very flexible and was unable to swim for long distances. At half a meter long, the fish is most similar to the garfish or needlefish, which are still alive today.

The fossil came from the Monte San Giorgio find in Ticino, declared a world heritage site in UNESCO in 2003.