Can a signet of capture work on a non-boss?

I've searched and did not find the answer for this one. Basically, I want earthquake.

Skel Sorcs in a mission in Krytia use this skill. I was wondering if I could capture from them or if the signet was limited to bosses only.

One can only capture skills from bosses

Bosses only. Sucks other wise you could get some really good skill really early.

Well, the boss version of a monster usually carries the skills of the ordinary monster. You might find earthquake on a boss skeleton sorc.