Cyclocystoids – Mysterious Fossils from the Cincinnatian Series
Posted On: 05/12/2017 - 2:06pm, Posted By: Brenda Hunda, Curator of Invertebrate Paleontology
You might think that after over 150 years of scientific research on our local rocks and fossils (Cincinnatian Series, 450 million years old) that scientists recognize and understand all the different species of fossil organisms that make up the ancient marine community in our local strata. Not so. This region is still a hotbed of scientific research. Paleontologists are constantly developing new insights into evolutionary relationships, community organization, and the paleobiology of some of the most common, and our favorite, fossil organisms. In addition, there are still new fossil organisms being discovered. Some species are so rare, we know very little about them.
Zygocycloides magnus from the Cincinnatian Series (450 million years old), Cincinnati area, CMC PT620.
One such fossil group are the cyclocystoids. Never heard of them? That’s okay. Most people have not. These fossils are so rare that a recent donation of three specimens by a member of the Dry Dredgers (our local amateur paleontological association) increased the number of these specimens in the Invertebrate Paleontology Collection at Cincinnati Museum Center by twenty percent.
Cyclocystoids are a little understood group belonging to the Phylum Echinodermata, along with starfish, sand dollars (echinoids), and crinoids. Features such as five-fold radial symmetry and a skeleton made up of interlocking calcium carbonate plates identify cyclocystoids as echinoderms. They range in age from the Early Ordovician (~470 million years ago) to the Early Carboniferous (~340 million years ago) and occur in North America and Europe. They are one of the rarest of Cincinnati's echinoderms. A ring of heavy plates that have small bumps around the outside and a middle portion that has radial lines characterizes them. They are small (about the size of a penny), delicate, and typically preserved as a ring of plates, making them easily overlooked in the field.
Reconstruction of the cyclocystoid Zygocycloides magnus. Sketch by Dr. Colin Sumrall, University of Tennessee. Courtesy of DryDredgers.org.
Paleontologists rely on hard part morphology and analogy with related, modern organisms (i.e. other living echinoderms) to reconstruct soft part anatomy and the biology of fossil organisms. Because cyclocystoids are typically found with incomplete hard parts and their odd structure is unlike any known modern echinoderm, their biology, soft part anatomy, and lifestyle is poorly understood. Even their digestive system (i.e. anus and mouth arrangement) isn't completely known. However, scientific studies continue to reveal more information about these rare creatures as more complete specimens are found. Recent research has shown that cyclocystoids were mobile, lived with their oral surface (mouth region) on the bottom, and most likely gathered food from the sediment surface.
If you are out collecting fossils, keep a lookout for cyclocystoids. You never know, the specimen you find might be the one to unlock all the clues to the mysterious lifestyle of this rare Cincinnatian fossil!