This video says about itself:
Body elongation in early fish evolution
7 Oct 2013
In Saurichthys, an early ray-finned fish, the vertebral arches of the axial skeleton are doubled, resulting in the elongation of the body and giving it a needlefish-like appearance. This video illustrates the hypothetical evolutionary transformation from a generalized fish in the late Permian to the specialized vertebral column and body shape of Saurichthys in the early Triassic.
Saurichthys: Unusual 240-Million-Year-Old Fossil Fish
Oct 8, 2013 by Enrico de Lazaro
A newly discovered fossil of an early ray-finned fish, named Saurichthys curionii, from the Middle Triassic of Switzerland reveals a previously unknown mechanism of axial skeleton elongation.
The extreme elongation of body axis occurred in one of two ways: through the elongation of the individual vertebrae of the vertebral column; or through the development of additional vertebrae and associated muscle segments.
Unlike other known fish with elongate bodies, the vertebral column of Saurichthys 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.
“Previously, we only knew about an increase in the number of vertebrae and muscle segments or the elongation of the individual vertebrae.”
According to Dr Maxwell and his colleagues, Saurichthys was certainly not as flexible as today’s eels and, unlike modern oceanic fishes such as tuna, was probably unable to swim for long distances at high speed.
Based upon its appearance and lifestyle, the roughly half-meter-long fish is most comparable to the garfish or needlefish that exist today.
- Fish Fossil Shows New Evolutionary Mechanism (scienceblog.com)
- Exceptional fossil fish reveals new evolutionary mechanism for body elongation (eurekalert.org)
- New fish fossil reveals unknown mechanism of spinal elongation (examiner.com)
- Ancient Fish Fossil Reveals How Elongate Animals Like Eels and Snakes May Have Evolved (scienceworldreport.com)
- New fossils push the origin of flowering plants back by 100 million years to the early Triassic (phys.org)