It's not a new argument, though.
Similar arguments have arisen from the fact that octopedes and alligators haven't changed much in millions of years, either. The basic idea is that if you can show that some organism hasn't evolved, therefore it follows that evolution is wrong.
This argument is operating under an assumption, one for which, once realized, quickly dismantles the argument - evolution doesn't say everything must evolve at all times.
The above visual aid will help me explain the relationship between evolutionary change and the environment.
Evolution, as a mechanism, trends the organism form towards being adapted to the environment. "The environment" is the sum total of factors that the organism has to deal with - such as the climate, the predators and prey in the area, incidents like a forest fire, or other events that comprise or change the surroundings over time.
If the environment doesn't change, there's no pressure for the organism to change. It'll tend to converge and stabilize in a particular form until the environment changes again.
For organisms like sharks and octopedes, this may be due to the fact that the environment of the ocean doesn't tend to change much, compared to land.
That might not account for alligators, though, however, some forms, like the basic concept of a fish, is well suited for multiple environments. Alligators don't have many predators, the basic concept of the environment has remained steady, and the food supply has remained basically the same (birds, fish, etc).
In short, there's nothing contradictory about a line of descent that hasn't experienced a lot of change in a few million years with evolution. In fact, this actually falls right in line with what we would expect from evolution.
It would be like saying that Fluid Dynamics (the study of the flow of water) is falsified because you found a stagnant puddle that isn't moving. It's silly.
What could falsify evolution, you ask? Off the top of my head, there are a number of things:
- If the fossil record showed the same creatures that exist now existed always (some can die off but we shouldn't see new ones appearing)
- If genetics showed that we had no relation to one another (though the fact that we all have this DNA/cell basis in common is an indicator of common ancestry)
- If it was shown that the Earth is too young to allow enough time for evolution (some do believe this, oddly)
Sadly for creationists, all evidence supports evolution, unambiguously.