The researchers set out to find out if the long-extinct Jurassic shark is the missing link between sharks and rays, or just a primitive ancestor of both.
Experts analyzed the rare well-preserved body of an ancient animal to see if it could be the ancestor of modern sharks and rays. However, scientists have received quite unexpected results. It turns out that by that time it was already very highly developed, writes IFLScience.
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The history of sharks is much older and begins long before the dinosaurs, namely about 400 million years ago. As a group, they managed to survive all five mass extinctions, and therefore their “family” ties can be traced in many lines.
However, studying them is quite difficult, because they are cartilaginous fish, that is, they do not have a bone skeleton as such, so in most cases only their teeth can be found in the fossil.
The exception, however, is the Konservat Lagerstätte in Bavaria, where Late Jurassic species (both bony and cartilaginous) are preserved in rock, where impressions of their skin, muscles, and other tissues are visible. As with flower herbarium applications, thanks to this we can get a certain even two-dimensional look of ancient animals, the specimens of which are incredibly rare.
One such species that has been found is Protospinax annectans. However, its place in shark evolution is still shrouded in mystery.
Approximately 150 million years ago, she swam in the expanses of the ocean, and her size reached 1.5 meters.
Approximately 150 million years ago, Protospinax annectans swam in the vastness of the ocean, and its size reached 1.5 meters
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Photo: Sebastian Stumpf
In addition, its place in evolution has been a subject of debate for many years. Was it an ancient ancestor of modern sharks and rays, and the missing link between these species? To find out, the researchers studied this specimen in detail, familiarized themselves with its unknown role through genetic data (mitochondrial DNA) and morphological data to reconstruct the shark family tree.
And here the results stunned the experts. It turns out that neither theory was confirmed, and for this species there is a third way.
Although Protospinax annectans has features of both sharks and rays, it is not a primitive ancestor of both, but a highly evolved shark in its day.
“We tend to think of evolution as a sort of hierarchical system with older groups at the bottom and humans, a very young species compared to others, at the top,” said study author Patrick L. Jambura. In fact, evolution never stopped even for these ancient representatives, because they also continue to evolve day by day due to changes in their DNA. Only thanks to this they were able to adapt to a changing environment and survive to this day.
However, it remains a mystery why Protopinax became extinct when other similar morphologically similar shark species survived. However, in the end, she was not a stepping stone or even a doorstep in the epic story of the sharks’ rich past.
Previously, Focus wrote about the found remains of a giant fish that hunted human ancestors. She could grow to over 2.5 meters in length and lived to about 360 million.
