curious about icon tot he left of monster's name

Secrets_ - Dreamweaver

i've seen at least 4 different types of "wings" as you would call it to the left of monsters sometimes
a little baby wing
a sharp wing
a large thick wing

also noticed a little white skull

highlighting them do not display anything except the skull (which i can't remember atm)

it bugs me not to know what the differences are or mobs marked with those wings are referred to and their differences.

Nowitsawn - Heavens Tear

The skull means the target is a boss monster, which means that it does more damage than its level suggests. Same with the wings, bigger wings means a more dangerous boss.