So what is the function of this grappling hook-like structure of this crinoid!? Well, rather than have suckers or roots to attach to the sea floor, paleontologists think this structure probably swiveled on the sea floor and hooked on to coral, seaweed, or other objects and thus held the animal in place. The specimen in the photo, called Ancyrocrinus, was collected in Clark Co., Indiana and is from the mid-Devonian (385 – 406 million years ago).