Catalog Number: CG-0025
February 2020 – I have updated this post. I received a more solid identification of Brachycycloceras after a visit to the Carnegie Museum.
June 2020 – I am again updating this post. I shared the photo of CM 29726 with Royal Mapes, who said that the specimen is defiantly not a Brachycycloceras. He said that the “open umbilicus, rate of coiling and the width of the conch” suggest Solenochilus. Going on this, I am reverting my identification of this back to Solenochilus. I contacted the museum and they agreed with Mapes assessment, thus re-labeling the specimen as Solenochilus.
The information below is currently out of date. I will need to update it to reflect the genus Solenchilus.
About Brachycycloceras
First described by Miller in 1933, the genus Brachycycloceras occurs from 326 million years ago up until the Permian extinction, 252 million years ago. This genus is relativity unknown to me. There are 5 valid species under the genus. They are:
| Genus | Species | Year | Describer |
|---|---|---|---|
| Brachycycloceras | curtum | 1869 | Meek and Worthen |
| Brachycycloceras | cyclophorum | 1879 | Waagen |
| Brachycycloceras | normale | 1855 | Miller et al. |
| Brachycycloceras | rustaqense | 1996 | Niko et al. |
| Brachycycloceras | washingtonense | 1964 | Gordon, Jr. |
It’s worth noting that the Encyclopedia of Ancient Life lists Brachycycloceras bransoni as a species.
This is by far the largest identifiable Cephalopod body chamber I have found to date. It came out of the hillside as a boulder but had a familiar body chamber shape. I could quickly identify it as a cephalopod, but I was unsure of the species. This particular specimen measures 5.5 inches wide by 9 inches long.
As usual, a specimen this large is also very fragmented and hard to see in detail past what you can see in the photos below. However, it is positive for being a shelled creature of this size.
US Quarter for scale 
Side view
Online and Offline References on Brachycycloceras
- Taxon Page – Fossilworks
- Genus Page – Digital Atlas of Ancient Life
- Brachycycloceras cf. curtum – Digital Atlas of Ancient Life
- Brachycycloceras normale – Digital Atlas of Ancient Life
- Brachycycloceras bransoni – Digital Atlas of Ancient Life
- 1980, Shimer, H.R., Shrock, R.R., Index Fossils of North America, Page 539
- 1997, Sturgeon, M. T., Windle, D. L. Jr., Mapes, R. H. and Hoare, R. D., Pennsylvanian cephalopods of Ohio. Part 1, nautiloid and bactritoid cephalopods. Ohio Division of Geological Survey, Bulletin 71, p. 1–191.