where can i get a dull claw? what beast drops it?

try Hunter wolves or creatures around the bluff mines. West of Archo city.

http://www.pwdatabase.com/pwi/items/8105
list of monsters that drop it is right there. No location means it doesn't exist.

i found that the shanlang clutass at 451 723 drop the dull claw more often

I think Midnight Jackalopardite dropped most for me

Well depends on ur lvl...
for 2x midnight jack is the best... 3x medium Sapphire Don

In my experience of all mobs under level 30, Snakevalley Bloodwolf lvl27, drops most Dull Claws of all. About 3-5 Dull Claws per 10 wolfs, never actualy counted average, I used to get about 40 Dull Claws per hour with my veno on them. Reason why they are better then Jackalopardites, is very simple, they die 3 times faster, so in order for Jacks to be better they should have 3 times plus more Dull Claw drop rate. They don't, jacks drop chance for claw is only about 3-4% percent bigger then wolfs. And moreover Snakevalley Bloodwolfs are 100% non agresive mobs, walking amongst some other non-agresive mobs.