Crinoid holdfast seen sideways in the Aigu Beds, Kaugatuma Stage, Pridoli. This structure is like the tap root of a tree. It penetrated the sediment, tapering downwards, and produced lateral branches (radices) which held the crinoid in place in a relatively energetic marine environment. Unlike a tree root system, this crinoid holdfast did not take up nutrients for the organism. Crinoids are animals which filter the seawater for food with a head and arms at the opposite end of the stalk.