Undersea Animal Gardens

       Most people who walk along here go past without even noticing me, but you heard me because you were bending over. You looked so interested in what you were doing that I wanted to help you, and so I asked you what you had picked up. You showed me the little object that you held in your hand.

       Perhaps you have seen such objects quite often along the beaches of Lake Michigan: small, round, flat little stones with a hole in the middle. Sometimes the children put them on strings and call them Indian beads. To look at these little stones you probably would never guess that they are parts of animals that lived here in Chicago ages ago. Of course there was no Chicago then. There weren't even any people, as a matter of fact, or any animals like the ones you know about today. The animals that lived then were very strange.

       The little round stones are parts of one of these strange animals. The name of the animal is crinoid, and perhaps it will be a surprise when I tell you that its nickname is sea-lily. That certainly seems like a strange name to use for an animal, but you wouldn't think the name so very strange if you could see one of the sea-lilies alive and whole. The crinoid or sea-lily was an animal that might easily fool you because it looked very much like a beautiful underwater plant.

       Crinoids lived together in groups, and a garden of these sea-lilies, although rather weird, was very beautiful, for crinoids were brilliantly colored. Some of them were patterned in many different ways.

       Try to imagine the strange but beautiful undersea gardens of plants that were really animals. Now think how a starfish would look if it were on its back, mouth up, because the sea-lily belongs to the same family as the starfish. The top or flower-like part of the ancient crinoid had five movable arms surrounding its mouth. Each arm branched into many more arms, all of them covered with feathery whips that swept microscopic animals down into the mouth of the crinoid.

       A stem was attached at one end to the middle of the crinoid's back or under side. The other end of the stem could fasten itself to the ocean bottom. Some of the prehistoric sea-lilies became anchored to one spot in this way. Some of them had almost no stems at all and others had extremely long stems. Most of the sea-lilies, however, had stems that were from one to three feet long. When the sea-lily was very young, it swam around in the shallow warm sea water; but when it grew older, it attached this long stem-like piece of itself to the ocean bottom. This stem was made of limy plates or segments, and each of them was like the one that you are holding in your hand.

       Besides the stem segments the crinoids had many hard parts that became fossilized. Unfortunately, these fossil pieces easily fell apart, and for this reason very few complete fossil crinoids have ever been found. Sea-lilies, however, are still living in many parts of the world, and so we know exactly how the prehistoric ones looked. But today these attached plant-like animals are very seldom seen because they live only in the deep parts of the oceans. Most of the crinoids that live now do not have stems and can swim freely in shallow water. They move about by folding and unfolding their arms.

       Of course, I haven't seen any of my ancient crinoid acquaintances around here for millions of years. But I am very often reminded of them when someone comes by and picks up part of their fossil remains.

Crinoid fossils in Crawfordsville, Indiana.