Hydra

Not what you expect, or?
The real hydra is extinct in the wild but a few specimens are alive in zoos (not normal zoos )
But how is it possible that the old greeks see something like this: [link]

The answer is, again, easier as the most think.
When the mating season is coming the smaller males of the region comes together and build a mating ball with one or two females (maybe you know that behavior from anacondas). And even in this state they can be very aggressive.
Dendroaspis is a member of the mambas and is able to rise the front half of it's body.