If I get assigned a normal type creature task, can I still kill it's corrupted counterpart and have it count?

With the recent Menaphos update to the game, corrupted creatures in the Sophanem slayer dungeon have been added. If you get assigned the slayer task "corrupted creatures," you can kill these for experience (or if you get a direct corrupted creature assignment obviously).

However, what if you are assigned the normal version of the task? For example, lets say I get assigned "Dust Devils." Does that mean I can only kill the regular ones for it to count towards the slayer task or can I also kill the Corrupted Dust Devils as well?

Yes, you will still earn experience and kills towards your task. I received a normal Dust Devil task from Kuradal today (coincidental to my example in my question), and decided to attempt to slay some corrupted versions of them. Happily, I received experience towards Slayer.