Angels in most renditions have bird wings (i.e. arms) growing from their backs in addition to normal arms and legs.

They could be extensions of the scapula. This would make the renditions where pegasus appears to be galloping while flying more accurate.

No alien species counts as an animal taxinomically. A similar extraterrestrial ecosystem would likely result in reclassifications to add planet of greatest ancestral origin. Life seeders would make taxonomy even harder.

Exactly.

I'd argue centaur world is its own tree of life until proof exists that earth life and centaur world life had a common ancestor.

sigh Okay scientist, you can look at my dragon dick

... For science

"Wait, what's the mould for?"

You mean, “sea bugs?”

Don't most of them have 8 or more limbs?