My little brother found this on our family's property in Arkansas. It appears to be some kind of fossil, any guesses as to what it is exactly? I don't know much about fossils so I'd appreciate any insight. I can take more pictures later if needed.
Those are fossil crinoid stems. There are still about 600 species of crinoids (sea lilies) living today. Nice find.. You might have some of the crinoid "heads" in there also.
@smokeythecat has it right. Note that, despite the use of terms like 'stem' and 'sea lily', these are animals not plants, and loosely related to starfish and sea urchins. The 'stem' is more usually called the 'columnal'.
Crinoids of this type first appeared in the Ordovician period around 480 million years ago and, although as said they aren't extinct, there are no known fossils which are more recent than 200 million years (and not from America).