An item in the usual science news reveals that snake and eel body plans have evolved separately many times over 500 million years.
My, my. Lotta years that.
And a 240 million year old fossil fish find shows a third way it could happen, according to reports:
A team of paleontologists from the University of Zurich headed by Professor Marcelo Sánchez-Villagra now reveal that a third, previously unknown mechanism of axial skeleton elongation characterized the early evolution of fishes, as shown by an exceptionally preserved form. Unlike other known fish with elongate bodies, the vertebral column of Saurichthys curionii does not have one vertebral arch per myomeric segment, but two, which is unique. This resulted in an elongation of the body and gave it an overall elongate appearance. “This evolutionary pattern for body elongation is new,” explains Erin Maxwell, a postdoc from Sánchez-Villagra’s group. “Previously, we only knew about an increase in the number of vertebrae and muscle segments or the elongation of the individual vertebrae.”
The researchers think the fish wasn’t as flexible as eels or snakes.