Synarmocrinus cobbani, a New Species of Crinoid


A friend, Bill Bateman, found a complete crinoid cup in the Minturn Formation, near the town of McCoy, Colorado. The Minturn Formation is Middle Pennsylvanian in age (about 300 million years old). A basal view of the cup, which is 38 mm wide, is shown above. The specimen is at the Denver Museum of Nature and Science. We have found some other specimens that are probably of the same species, but none of them compare in completeness or preservation to this one. After a lot of library research and some consultation with Gary Webster of Washington State University, we decided that it was a new species. Bill named it Synarmocrinus cobbani, after Dr. William Cobban, an invertebrate paleontologist who specializes in Cretaceous ammonites. The formal species description was published in an article titled "Synarmocrinus cobbani, a new crinoid from the Minturn Formation (Middle Pennsylvanian) of Colorado" by W. M. Itano and W. D. Bateman, in The Mountain Geologist, vol. 38, April 2001, p. 71-76. The Mountain Geologist is published by the Rocky Mountain Association of Geologists. The abstract of the article is given below:

"Synarmocrinus cobbani, new species, is reported from the Minturn Formation (Pennsylvanian, late Atokan), McCoy, Eagle County, Colorado. This is the second species of Synarmocrinus and the eighth cromyocrinid reported from the Minturn Formation. The holotype is a complete cup, which is medium globe-shaped, has a shallow basal concavity, and contains two anal plates. The primanal is large and quadrangular; the secundanal is narrow, extends above the cup, and makes a narrow contact with the CD basal. S. cobbani is distinguished from all other species of Synarmocrinus by the surface ornament, which consists of numerous, widely- spaced nodes, sometimes connected by ridges, and by other details of the cup shape and cup plates."

Wayne Itano

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Last modified: May 28, 2001. Send comments to