Some of these names are not much used and usually people dislike them (Koala bear, instead just Koala). But most of them are widely used. Euphorbia cactus is much less used than any of them, I never saw it before. Everybody call them just "Spurges" (with some exceptions, like Pasque flower), or use the scientific "Euphorbia".
Anyway... these are only common names. So, no rules, no chances to be valid or invalid. Everybody can call an organism like he want
Some of these names are not much used and usually people dislike them (Koala bear, instead just Koala). But most of them are widely used. Euphorbia cactus is much less used than any of them, I never saw it before. Everybody call them just "Spurges" (with some exceptions, like Pasque flower), or use the scientific "Euphorbia".
Anyway... these are only common names. So, no rules, no chances to be valid or invalid. Everybody can call an organism like he want
Quite correct in everything you said (except for two things), I was merely pointing out that there are many similar names in common usage.
The two exceptions - Flying Fox, Mountain Chicken, Sand Fish, Horned Toad, Sea Lion and Guinea Pig are all in very common usage; and in Uganda at least, "Euphorbia Cactus" is the common name there, and it's what the local Parks & Wildlife Rangers call it too.
However, you'll see I've changed the title of the image to it's botanical name.
