And now one of the strangest objects in the Rover collection. Look what decided to poke its head out of the sand to take a look at the little robot that must surely be disturbing it.

Another Rock! If I didn't know better I'd say that looks like some type of reptile,
so I laughingly call it "the Turtlehead", knowing such things are impossible on Mars

 however, notice that the sand covering it was dislodged by its motion, and look behind it.
Have you ever been buried in the sand at the beach?
What happens to the sand covering your arms and legs when you move them a little?

But of course, Rocks don't move

Might that look a bit like what's happening here?

Below it may just be another, only it is still buried.

 
Notice there's some type of "tube" sticking out of the ground just above midway up the rover antenna's shadow, below the exposed "Turtlehead". Here are two comparative views from slightly different times.

Were there life on Mars, I'd imagine it may survive by being burrowed into the moist warm and fluffy dust, coming out to sun itself and hunt on the warm surface occasionally. Surely it would be well adapted to its native world, and perhaps quite hardly. We know Mars has subsurface water, we know its dust is light bodied and its gravity much less, Perhaps we've been looking at creatures all along and nobody noticed?