They focus too much on special characteristics and ignore common rules.

Not only current authors, but the writers of ancient myths also do that (we should give them more tolerance because there was not much of science at that time).

Fictional worlds, more or less, are based on our own world.

*Whisper* It is said in our fandom that if you find a picture of the western part of (Third Age) Middle-earth and rotate it 45 degree anticlockwise, you will have special discoveries.

But it’s fiction, so it has to have special things. Writers usually create fantastic things and beings by focusing on some special aspects of things in our world and exaggerate them, or put them together.

That’s fine, it’s fiction! But we have to give our fictional creatures some ways to live their lives, right?

Like… I truly feel sorry for the mermaids. They are charming, poetic, but their lives are not easy.

Fish, whales and ichthyosaurs (ancient reptiles shaped like fish) keep balance using their dorsal fins. But in most versions the mermaids have fish-like tails but don’t have dorsal fins. That will make them easy to turn aside and difficult to swim properly. (They can use hands but it’s slower and takes more energy.)

Moreover, human vocal organs are nearly useless underwater (try it yourself). So the mermaids can’t sing like humans. I suppose they sing like dolphins.

Centaurs. (The one on the right is one of them.)

Fascinating creatures. They are mammals, right? However… they actually have six legs! Where did they get the additional ones? Poor kids!

Samodivas.

(Rare case of an offspring of a Samodiva/Veela. She is astonishingly beautiful, it’s hard to imagine how her grandma would be like.)

Recorded Samodivas are all female, and they hardly mate any human. They only exhaust them and gain their energy. So…How do they reproduce? Do they clone themselves? Or perform parthenogenesis? Like…

Finally…Looookiiii!

…And his whole nation of icy giants.

In Marvel movies they seem to be huge on their planet, along with some animals even larger than them. No plants and smaller animals are shown. They appear to jump out from nowhere. And there is not much of solar power. In the original Norse Mythology Jotunheim is not such a barren place. But in the movies…??

These creatures are all part human combined with a certain feature or aspect of nature. Unluckily, writers often exaggerate this feature so much that it makes their species unable to survive.

P.s. I truly love fantasy. I just hope the works can be more “real”.