Modern Sharks Sleeker Than Ancestors: Page 2

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The arrangement of these skeletal features in Ozarcus resembles that of bony fish, so it can now be inferred that the common ancestor of bony fishes and cartilaginous fishes was more like a bony fish than a shark. Bony fishes may then provide greater clues about our first jawed ancestors than modern sharks do.

This is significant, especially for researchers working to unravel the early stages of vertebrate evolution. One such scientist is Philippe Janvier, a vertebrate paleontologist at the Museum National de l’Histoire Naturelle in Paris.

Janvier told Discovery News that “we are probably confronted with a radical change in our views about what is primitive and what is advanced in jawed vertebrate evolution.”

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He and his colleagues are now beginning to consider that “sharks and their allies may well be the anatomically most advanced jawed vertebrates, which evolved through a considerable reduction of their ability to produce bone,” Janvier said.

Without heavy bones, sharks evolved into faster, lighter and more flexible hunters.

Many exhibit what Pradel calls a “fusiform” shape, meaning wider in the middle and tapered at the ends. Most sharks have this streamlined shape, as do tuna, dolphins and certain other swift-swimming predators.

It’s possible, but not likely, that sharks could de-evolve their traits. Species can undergo so-called backward evolution into more “primitive” forms over time, depending on what features best support current conditions. What’s even more essential is that the evolution of a species can keep up with environmental shifts, such as climate change.

Sharks—even with their modern features—tend to repopulate slowly, making them extremely vulnerable to overfishing, climate change and other human-affected threats.

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