Isn't there a chart for Knowledge Checks?

[Jhulae]

I thought the formula was 10+CR. Doesn't make a whole lot of sense to base it off HD.

Nope.

In many cases, you can use this skill to identify monsters and their special powers or vulnerabilities. In general, the DC of such a check equals 10 + the monster’s HD. A successful check allows you to remember a bit of useful information about that monster.

For every 5 points by which your check result exceeds the DC, you recall another piece of useful information.

Which means.. if your knowledge check is a 24 (for example) and you recall no useful information, you still figured out *something*...

 

[lottrbacchus]

Hmmm, the autopsy thing and special abilities. You'd have to decide if the creature has some special organs or if it is just channeling some magical energy.